WO2012078517A1

WO2012078517A1 - Inks for solar cell inverted structures

Info

Publication number: WO2012078517A1
Application number: PCT/US2011/063300
Authority: WO
Inventors: Caton C. Goodman; Edward S. Yang
Original assignee: Plextronics, Inc.
Priority date: 2010-12-06
Filing date: 2011-12-05
Publication date: 2012-06-14

Abstract

Compositions and devices comprising at least one conjugated polymer and at least one fluorosurfactant, providing improved wettability. Compositions can be applied to substrates and used in HTL layers in organic electronic devices such as inverted photovoltaic devices. The conjugated polymer can be a polythiophene. The fluorosurfactant can be a perfluorobutane sulfonate fluorosurfactant. Improved methods of making and using the HTL ink composition are provided.

Description

INKS FOR SOLAR CELL INVERTED STRUCTURES

BACKGROUND

Although useful advances are being made in energy saving devices such as, for example, organic-based organic light emitting diodes (OLEDs), polymer light emitting diodes (PLEDs), phosphorescent organic light emitting diodes (PHOLEDs), and organic photovoltaic devices (OPVs), further improvements are still needed in providing better processing and performance for commercialization. It is important to have very good control over the solubility of alternating layers of polymer (e.g., orthogonal or alternating solubility properties among adjacent layers). In particular, for example, hole injection layers and hole transport layers can present difficult problems in view of competing demands and the need for very thin, but high quality, films.

A need exists for a good platform system to control properties of hole injection and transport layers such as adhesion, solubility, thermal stability, and electronic energy levels such as HOMO and LUMO, so that the materials can be adapted for different applications and to function with different materials such as light emitting layers, active layers, and electrodes. In particular, good adhesion, solubility, intractability, and thermal stability properties are important. The ability to formulate the system for a particular application and provide the required balance of properties are also important. For example, the inverted solar cell structure is a particular application which provides particular demands in performance.

SUMMARY

Embodiments described herein include, for example, compositions, devices and articles, methods of making devices, compositions, and articles, and methods of using devices, compositions, and articles.

For example, provided herein is a device including a substrate, a first electrode formed on the substrate, a hole blocking layer formed on the first electrode, a active layer formed on the hole blocking layer, a hole transport layer formed on the active layer, and a second electrode formed on the hole transport layer, wherein the hole transport layer comprises at least one conjugated polymer and a fluorosurfactant. In some embodiments, the hole transport layer is disposed between the active layer and the anode.

Another embodiment provides a method of forming a device including the steps of providing a substrate, forming a first electrode on the substrate, forming an hole blocking layer on the first electrode, forming a active layer on the hole blocking layer, forming a hole transport layer on the second active layer, and forming a second electrode on the hole transport layer, wherein the hole transport layer comprises at least one conjugated polymer and a fluorosurfactant.

In one embodiment, an ink composition for forming the hole transport layer of an inverted photovoltaic device is provided, wherein the composition comprises hole transport materials and a fluorosurfactant.

Another embodiment provides an ink composition for forming the hole transport layer of a photovoltaic device, the composition comprising at least one solvent and dissolved components, the dissolved components comprising at least one conjugated polymer and a fluorosurfactant

Another embodiment provides a method of forming an ink usable for deposition as the hole transport layer of a photovoltaic device, the method comprising: (A) providing a first solvent, (B) providing a conjugated polymer, (C) providing an organic polymer different from (B), (D) providing a fluorosurfactant, (E) providing a second solvent, and (F) combining in any order (A), (B), (C), (D) and (E) to form an ink composition.

At least one advantage in at least on embodiment is better wetting of HTL layer.

At least one more advantage in at least one embodiment is ease of spinning the HTL layer on to the anode or the active layer or possibly other coating methods.

At least one more advantage in at least one embodiment is reduce or eliminate the need for pretreatment of active or electrode layers, which involves additional steps and can be deleterious to device performance.

At least one more advantage in at least one embodiment is improved device manufacturing.

At least one more advantage in at least one embodiment is better stability and lifetime.

Additional advantages include improved adherence and film uniformity. BRIEF DESCRIPTION OF FIGURES

Fig. 1 is a schematic of a conventional solar cell structure.

Fig. 2 is a schematic of a conventional inverted solar cell structure.

DETAILED DESCRIPTION

INTRODUCTION

Various terms are further described herein below:

"About," as used herein in conjunction with a stated numerical value, refers to a value within ±10% of the stated numerical value.

As used herein, and unless otherwise specified, "a" or "an" refers to "one or more."

"Alkyl" can be for example straight chain and branched monovalent alkyl groups having from 1 to 20 carbon atoms, or from 1 to 15 carbon atoms, or from 1 to 10, or from 1 to 5, or from 1 to 3 carbon atoms. This term is exemplified by groups such as for example methyl, ethyl, n-propyl, z^'so-propyl, n-butyl, t-butyl, n-pentyl, ethylhexyl, dodecyl, isopentyl, and the like.

"Optionally substituted" groups can be for example functional groups that may be substituted or unsubstituted by additional functional groups. For example, when a group is unsubstituted by an additional group it can be referred to as the group name, for example alkyl or aryl. When a group is substituted with additional functional groups it may more generically be referred to as substituted alkyl or substituted aryl.

"Substituted alkyl" can be for example an alkyl group having from 1 to 3, and preferably 1 to 2, substituents selected from the group consisting of alkyl, substituted alkyl, alkoxy, substituted alkoxy, aryl, substituted aryl, aryloxy, substituted aryloxy, hydroxyl.

"Aryl" can be for example a monovalent aromatic carbocyclic group of from 6 to 14 carbon atoms having a single ring (e.g., phenyl) or multiple condensed rings (e.g., naphthyl or anthryl) which condensed rings may or may not be aromatic provided that the point of attachment is at an aromatic carbon atom. Preferred aryls include phenyl, naphthyl, and the like.

"Substituted aryl" can be for example to an aryl group with from 1 to 5 substituents, or optionally from 1 to 3 substituents, or optionally from 1 to 2 substituents, selected from the group consisting of hydroxy, alkyl, substituted alkyl, alkoxy, substituted alkoxy, alkenyl, substituted alkenyl, substituted aryl, aryloxy, substituted aryloxy, and sulfonate

"Alkoxy" can be for example the group "alkyl-O-" which includes, by way of example, methoxy, ethoxy, n-propyloxy, z^'so -propyloxy, n-butyloxy, t-butyloxy, n- pentyloxy, 1-ethylhex-l-yloxy, dodecyloxy, isopentyloxy, and the like.

"Substituted alkoxy" can be for example the group "substituted alkyl-O-."

"Alkylene" can be for example straight chain and branched divalent alkyl groups having from 1 to 20 carbon atoms, or from 1 to 15 carbon atoms, or from 1 to 10, or from 1 to 5, or from 1 to 3 carbon atoms. This term is exemplified by groups such as methylene, ethylene, n-propylene, z^'so-propylene, n-butylene, t-butylene, n- pentylene, ethylhexylene, dodecylene, isopentylene, and the like.

"Alkenyl" can be for example an alkenyl group preferably having from 2 to 6 carbon atoms and more preferably 2 to 4 carbon atoms and having at least 1 and preferably from 1-2 sites of alkenyl unsaturation. Such groups are exemplified by vinyl, allyl, but-3-en-l-yl, and the like.

"Substituted alkenyl" can be for example alkenyl groups having from 1 to 3 substituents, and preferably 1 to 2 substituents, selected from the group consisting of alkoxy, substituted alkoxy, acyl, acylamino, acyloxy, amino, substituted amino, aminoacyl, aryl, substituted aryl, aryloxy, substituted aryloxy, cyano, halogen, hydroxyl, nitro, carboxyl, carboxyl esters, cycloalkyl, substituted cycloalkyl, heteroaryl, substituted heteroaryl, heterocyclic, and substituted heterocyclic with the proviso that any hydroxyl substitution is not attached to a vinyl (unsaturated) carbon atom.

"Aryloxy" can be for example the group aryl-O- that includes, by way of example, phenoxy, naphthoxy, and the like.

"Substituted aryloxy" can be for example substituted aryl-O- groups.

"Alkylene oxide" can be, for example, the group -(R^a-0)_n-R^b where R^a is alkylene and R^b is alkyl or optionally substituted aryl and n is an integer from 1 to 6, or from 1 to 3. Alkylene oxide can be for example groups based on such as groups as ethylene oxides or propylene oxides.

"Salt" can be, for example, derived from a variety of organic and inorganic counter ions well known in the art and include, by way of example only, sodium, potassium, calcium, magnesium, ammonium, tetraalkylammonium, and the like; and when the molecule contains a basic functionality, salts of organic or inorganic acids, such as hydrochloride, hydrobromide, tartrate, mesylate, acetate, maleate, oxalate and the like.

In substituted groups described above, polymers arrived at by describing substituents with further substituents to themselves (e.g., substituted aryl having a substituted aryl group as a substituent which is itself substituted with a substituted aryl group, etc.) are not intended for inclusion herein. In such cases, the maximum number of such substituents is three. That is to say that each of the above descriptions can be constrained by a limitation that, for example, substituted aryl groups are limited to -substituted aryl-(substituted aryl)-substituted aryl.

Similarly, the above descriptions are not intended to include impermissible substitution patterns (e.g., methyl substituted with 5 fluoro groups or a hydroxyl group alpha to ethenylic or acetylenic unsaturation). Such impermissible substitution patterns are well known to the skilled artisan.

All references described herein are hereby incorporated by reference in their entirety.

One skilled in the art can employ the following references in the practice of the various embodiments described herein. In particular, several references describe conducting polymers, polythiophenes, regioregular polythiophenes, substituted polythiophenes, and OLED, PLED, and PV devices prepared from them, and these can be used in the practice of one or more of the present embodiments. In reciting a conducting polymer name, the name can also include derivatives thereof. For example, polythiophene can include polythiophene derivatives.

Electrically conductive polymers are described in The Encyclopedia of Polymer Science and Engineering, Wiley, 1990, pages 298-300, including

polyacetylene, poly(p-phenylene), poly(p-phenylene sulfide), polypyrrole, and polythiophene, which is hereby incorporated by reference in its entirety. This reference also describes blending and copolymerization of polymers, including block copolymer formation.

Homopolymers are generally known in the art. See for example Elias, An Introduction to Polymer Science, VCH, 1997, Chapter 2. Copolymers and copolymer architecture are also generally known in the art. See, for example, Billmeyer, Textbook of Polymer Science, 3rd Ed, 1984 (e.g., Chapter 5); Concise Encyclopedia of Polymer Science and Engineering, (Kroschwitz, Ed.), 1990 "Copolymerization" and "Alternating Copolymers." As an example, copolymers include block copolymers, segmented copolymers, graft, alternating copolymers, random copolymers, and the like. Copolymers include polymers with two or more different types of repeat groups, including terpolymers.

Conjugated polymers are also generally known in the art. The homopolymers and copolymers described herein are examples. Other examples include

polythiophenes (including regioregular polythiophene derivatives), polypyrroles, poly(phenylene vinylenes), polyanilines, and the like.

U.S. Patent 6,166,172 describes the GRIM method of forming, for example, a regioregular poly (3 -substituted thiophene) from a polymerization reaction. The method proceeds by combining, for example, a soluble thiophene having at least two leaving groups with an organometal, e.g., organomagnesium, reagent to form a regiochemical isomer intermediate, and adding thereto an effective amount of, for example, Ni(II) complex to initiate the polymerization reaction.

US Patent Application 11/826,394 filed July 13, 2007 to Sheshadri, incorporated by reference in its entirety, describes compositions, methods, and polymers comprising, for example, regioregular, sulfonated poly(3-substituted thiophene). .

Organic electronic devices are known in the art. OPV devices are generally described in, for example, Sun and Sariciftci (Eds), Organic Photovoltaics,

Mechanisms, Materials, and Devices, 2005, CRC Press.

Donors and acceptors are described in US Patent Application 11/745,587 to Laird et al, filed May 2, 2007, and US Patent Application 12/340,587 to Laird et al, filed December 19, 2008, both of which are incorporated by reference in their entirety.

Additional description of methods may be found in, for example, McCullough et al, J. Org. Chem., 1993, 58, 904-912, and U.S. Pat. No. 6,602,974, including formation of block copolymers, to McCullough, et al.

Additional description can be found in the articles, "The Chemistry of Conducting Polythiophenes," by Richard D. McCullough, Adv. Mater. 1998, 10, No. 2, 93-116, and references cited therein, and Lowe, et al, Adv. Mater. 1999, 11, 250, which are hereby incorporated by reference in its entirety. The Handbook of Conducting Polymers, 2nd Ed., 1998, Chapter 9, by McCullough, et al, "Regioregular, Head-to-Tail Coupled Poly(3-alkylthiophene) and its Derivatives," pages 225 258, is also hereby incorporated by reference in its entirety.

Solar cell panels or modules are well known in the art and are used widely to convert sunlight into electrical power. The panels or modules can comprise a plurality of solar cells, wherein each solar cell can be characterized by parameters known in the art including conversion efficiency and lifetime (T₅o). A solar panel or module can comprise a front side made of, for example, glass, interconnected solar cells, an embedding material, and a rear-side structure. See for example U.S. Pat. No. 7,049,803. The front-side glass can provide protection against mechanical and atmospheric influences. The glass may also provide suitable absorption and transmission of sunlight.

Photovoltaic modules or panels are generally known. See for example U.S. Pat. No. 6,329,588 to Zander et al; U.S. Pat. No. 6,391,458 to Zander et al; U.S. Pat. No. 7,049,803 to Dorner et al. Large-area photovoltaic cells are generally known. See for example U.S. Pat. No. 4,385,102 to Fitzky et al. Additional examples of solar cell panels are described in for example U.S. Pat. Nos. 4,830,038 to Anderson et al;

5,008,062 to Anderson et al; and 4,638,111 and 4,461,922 to Gay.

Solar cell materials are generally described in M. A. Green, Third Generation Photo voltaics; Advanced Solar Energy Conversion, Springer-Verlag, Berlin, 2004. Solar farms are generally known in the art and can be large-scale commercial power production sites. Solar farms can be used, for example, on rooftops or in open fields. A solar farm can employ methods known in the art, and raising and tilting solar panels to track the sun, concentrating the sunlight, converting DC to AC by inverters, etc.

Solar panels have been in large-scale use in solar farms for harvesting solar energy. Solar active materials having high energy conversion efficiency and long lifetimes are preferred. This invention relates, in some embodiments, to inverted solar cell structures in which the active inversion layer or the depletion layer is at the rear of the solar cell away from the incident light direction.

Printed solar panels are described in U.S. Patent Application Pub. No.

2005/0247340 to Zeira et al.

Electron-hole pairs (excitons) are typically bound unless they dissociate at the interface of a donor (p-type) and acceptor (n-type) semiconductors. Thus, exciton dissociation is dependent on the efficient diffusion of excitons generated toward the interface. However, exciton diffusion length is typically very short relative to the thickness of donor and acceptor material layers. To achieve optimum device performance, it has been thought desirable to have multilayer structures having discrete hole transport layer (HTL), emissive layer (EML), and hole blocking layer (HBL) or electron transport layer (ETL) functions. Conventionally, a HTL layer is introduced between the anode and the polymeric active layer in order to reduce the potential barrier at the polymer-HTL contact interface. The role of the HTL is not only to maximize hole injection from the anode, but also to block efficiency-depleting electron overflow from, and to confine excitons within the EML. Typical small- molecule HTLs are triarylamine-based materials such as NPB or TPD, which are known to have appreciable hole-transporting and electron-blocking capacity, because of their relatively high-lying LUMO levels and large HOMO-LUMO gaps.

DEVICE STRUCTURE

Various devices can be fabricated in many cases using multilayered structures which can be prepared by for example solution or vacuum processing, as well as printing and patterning processes. In particular, use of the embodiments described herein for hole transport can be carried out effectively. In particular, applications include hole injection layer for OLEDs, PLEDs, photovoltaic cells, supercapacitors, cation transducers, drug release, electrochromics, sensors, FETs, actuators, and membranes. Another application is as an electrode modifier including an electrode modifier for an organic field effect transistor (OFETS). Other applications include those in the field of printed electronics, printed electronics devices, and roll-to-roll production processes.

For example, photovoltaic devices are known in the art. The devices can comprise, for example, multi-layer structures including for example an anode such as ITO on glass or PET; a hole injection layer; a P/N bulk heterojunction layer; a conditioning layer such as LiF; and a cathode such as for example Ca, Al, or Ba. Devices can be adapted to allow for current density versus voltage measurements.

Similarly, OLED devices are known in the art. The devices can comprise, for example, multi-layer structures including for example an anode such as ITO on glass or PET or PEN; a hole injection layer; an electroluminescent layer such as a polymer layer; a conditioning layer such as LiF, and a cathode such as for example Ca, Al, or Ba. Methods known in the art can be used to fabricate devices including for example OLED and OPV devices. Methods known in the art can be used to measure brightness, efficiency, and lifetimes. OLED patents include for example US Patent Nos. 4,356,429 and 4,539,507 (Kodak). Conducting polymers which emit light are described in for example US Patent Nos. 5,247,190 and 5,401,827 (Cambridge Display Technologies). See also Kraft et al, "Electroluminescent Conjugated Polymers - Seeing Polymers in a New Light," Angew. Chem. Int. Ed., 1998, 37, 402- 428, including device architecture, physical principles, solution processing, multilayering, blends, and materials synthesis and formulation, which is hereby incorporated by reference in its entirety.

In conventional OPV devices the architecture is as shown in Figure 1, wherein an anode 120 such as a transparent conducting electrode, for example ITO, is formed on a substrate 110, such as glass or PET. A hole injection layer(HTL) 130 is formed on and in electrical contact with the anode. The active layer 140, such as a P/N bulk heterojunction, is formed on the hole injection layer. A cathode comprising, for example, Ca, Al or Ba, is formed on the active layer. The cathode may be a bilayer cathode comprising a first layer 150 of, for example Ca, and a second layer 160 of, for example Al. In a typical process, the ITO pattern on glass is spin coated with the Hole Transport Layer and annealed. The active ink is then spin coated on top of the HTL and annealed and cathode layer is then vapor deposited on to the active layer.

An inverted structure, shown in Figure 2, comprises substrate 110 such as glass or PET with an cathode 120, comprising for example ITO, formed on the substrate. An hole blocking layer (HBL) 170, comprising for example ZnO, is formed on the cathode. A active layer 140, such as a P/N bulk heterojunction, is formed on the hole blocking layer. The HTL 130 is formed on to the active layer and an anode 150 such as Ag or other high work- function metal is deposited on to the HTL layer. Due to the electron-transport or hole-blocking layer, in operation, electrons generated in the active layer are collected by the front cathode electrode, while holes are collected by the back anode. The inverse the architecture requires the HTL to be spun on the active layer. The HTL currently used for standard OPV devices does not wet well when spun on top of such inverted architectures.

Under short circuit conditions, the built in potential of a typical solar cell (which is based on the difference between the work functions of the cathode and anode) causes the electrons photogenerated in the active layer to drift toward the electropositive (lower work- function) electrode such as a calcium electrode as the cathode, and the holes photogenerated in the active layer to drift toward the more electronegative (higher work-function) ITO electrode as the anode.

In an inverted solar cell, a dielectric trapping layer can be used to enhance light trapping. Thus, an hole blocking (electron transporting) layer (ETL), typically comprised of metal oxides, is placed between an active layer and the cathode. The lower work- function electrode is replaced with a higher work function (more electronegative) electrode such as Ag or Al. Thus, since holes are blocked from traversing into the ITO electrode, they drift toward the Ag or Al electrode now serving as the anode. The ITO, now serving as the cathode, accepts electrons crossing through the hole blocking layer. In some embodiments, an n-type semiconductor ETL such as Ti0₂, ZnO, Cs₂C0₃ or W0₃ can be used.

In one aspect, a device is provided, wherein the device comprises a substrate; at least one cathode; at least one anode; at least one active layer disposed between the cathode and anode; and at least one hole transport layer; wherein the hole transport layer comprises a composition comprising: at least one hole transport material; and at least one fluorosurfactant.

In some embodiments, the hole transport layer is disposed between the active layer and the anode.

In some embodiments, the device comprises a substrate; a first electrode formed on the substrate; a hole blocking layer formed on the first electrode; an active layer formed on the hole blocking layer; a hole transport layer formed on the active layer; and a second electrode formed on the hole transport layer; wherein the hole transport layer comprises a composition comprising hole transport material and at least one fluorosurfactant.

Substrates of the present invention may comprise rigid glass substrates, flexible substrates such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) substrates or other flexible material that may be used as substrates for flexible devices such as flexible OPV devices, e.g., as metal foils (such as stainless steel foils), silicon wafers, and plastic.

The first electrode can either be a cathode or an anode. In some embodiments, the first electrode is a cathode. The first electrode can be formed of Indium Tin Oxide (ITO) or other transparent conductive oxides such as Indium Zinc Oxide (IZO), Aluminum doped Zinc Oxide (AZO), commercially available materials such as LR15 (CP Films) or the like. Such transparent lower electrode materials when used in combination with a transparent substrate, such as glass, allow for light emission from the OLED device to be viewed through the substrate.

The hole blocking layer or the electron transport layer can be formed of an n- type semiconducting transparent oxide such as Ti0₂, ZnO, or Cs₂C0₃. This layer is typically included for better matching of electron transport states and improved electron collection.

An exemplary active layer is formed as a bulk heterojunction comprising a conjugated polymer such as polythiophene and regioregular polythiophene p-type material, and at least one fullerene derivative as an n-type material. Examples of uses of such active layers, such as in an OPV device, are discussed in U.S. Published Application No. 2008/0319207 to Laird et al. (Plextronics, Inc.; Nano-C, Inc.) filed on February 29, 2008, and which is hereby incorporated by reference in its entirety.

The donor can be a p-type material comprising a conjugated polymer such as a polythiophene and regioregular polythiophene, for example a regioregular poly(substitutedthiophene), poly(3-substitutedthiophene) or poly(3-hexylthiophene).

The acceptor can be an n-type material comprising at least one fullerene derivate, where the fullerene can be C60, C70, or C84. The fullerene derivative can be for example, PCBM. The fullerene can also be functionalized with indene groups, for example, indene-fullerene. Thus, a composition of the active layer can comprise a blend of a donor polymer and an acceptor fullerene derivative.

The second electrode can either be a cathode or an anode. In some embodiments, the second electrode is an anode. The second electrode can be made of a suitable metal such as Ag, Au, Ca, Al or combinations thereof. In some

embodiments, the anode may comprise a high work function metal such as Ag. In some embodiments, the anode material may comprise a metal nanowire, such as a silver nanowire. It can be at least 30-200 nm thick.

The hole transport layer in the devices can comprise a HTL ink composition described below. In some embodiments, the HTL ink composition comprises a conjugated polymer and a fluorosurfactant.

HTL INK COMPOSITIONS In one aspect, an ink composition for forming the hole transport layer of a photovoltaic device is provided. In some embodiments, of the device is an inverted photovoltaic device. In some embodiments, the ink composition comprises hole transport materials and a flurorosurfactant. In some embodiments, the ink

composition comprises at least one solvent and dissolved components, the dissolved components comprising hole transport materials and a fluorosurfactant.

Examples of hole transport materials (HTL) include those described in U.S. Patent Application Pub. No. 2006/0175582 to Hammond et al. (Hole Injection Layer Compositions) and U.S. Provisional Patent Application Ser. No. 60/832,095 filed Jul. 21, 2006 to Seshadri et al.

In some embodiments, the hole transport materials may include polymeric materials including conjugated polymers, e.g., regioregular and non-regioregular polymers and other organic polymers different from the conjugated polymers.

Electrically conductive or conjugated polymers are described, for example, in The Encyclopedia of Polymer Science and Engineering, Wiley, 1990, pages 298-300, including polyacetylene, poly(p-phenylene), poly(p-phenylene sulfide), polypyrrole, and polythiophene, which is hereby incorporated by reference in its entirety. This reference also describes blending and copolymerization of polymers, including block copolymer formation.

The conjugated polymer can comprise at least one backbone repeat unit comprising a heterocyclic ring. In particular, the conjugated polymer can comprise at least one backbone repeat unit comprising a thiophene ring. Polythiophenes are particularly well-suited for the present applications. In particular, the conjugated polymer can comprise a regioregular polythiophene, wherein at least some of the thiophene rings are substituted.

Regioregularity of polymers is known in the art and the degree of

regioregularity can be for example at least about 70%, at least about 80%, at least about 90%), at least about 95%, at least about 98%>, or at least about 99%.

In some embodiments, the HTL and active layer materials may comprise sulfonated polythiophenes. Sulfonated polythiophenes are described, for example, in US Patent Application 11/826,394 filed July 13, 2007 to Sheshadri. In some embodiments, the aforementioned polymers can be subjected to sulfonation by methods known in the art commonly described in the patent literature including for example US Patent No. 5,548,060 to Allcock et al; 6,365,294 to Pintauro et al; 5,137,991 to Epstein et al; and 5,993,694 to Ito et al. Additional sulfonation methods are described in for example (1) Sotzing, G. A. Substituted thieno[3,4-b]thiophene polymers, method of making and use thereof, US2005/0124784 Al; (2) Lee, B.;

Seshadri, V.; Sotzing, G.A. Ring Sulfonated poly(thieno[3,4-b]thiophene), Adv. Mater. 2005, 17, 1792.

In an embodiment for the polymer which can be subjected to sulfonation to produce sulfonated substituents on the polymer backbone can be represented by formula (I),

(I)

wherein R can be optionally substituted alkyl, optionally substituted alkoxy, and optionally substituted aryloxy. Examples of substituents for the optional substitution include hydroxyl, phenyl, and additional optionally substituted alkoxy groups. The alkoxy groups can be in turn optionally substituted with hydroxyl, phenyl, or alkoxy groups; or

wherein R can be an optionally substituted alkylene oxide. Substituents can be for example hydroxyl, phenyl, or alkoxy groups; or

wherein R can be optionally substituted ethylene oxide or optionally substituted propylene oxide or other lower alkyleneoxy units. Substituents can be for example hydroxyl, phenyl, or alkoxy groups; or

R can be an optionally substituted alkylene such as for example methylene or ethylene, with substituents being for example optionally substituted alkyleneoxy such as ethyl eneoxy or propyl eneoxy; substituents can be for example hydroxyl, phenyl, or alkoxy.

In addition, the substitutent group R in (I) can be linked to the thiophene by an oxygen atom as alkoxy or phenoxy, wherein the substituent can be characterized by the corresponding alcohol or phenol, respectively. The alcohol, for example, can be linear or branched, and can have C2 - C20, or C4 - C18, or C6 to C14 carbon atoms. The alcohol can be for example an alkyl alcohol, or an ethylene glycol, or a propylene glycol, or a diethylene glycol, or a dipropylene glycol, or a tripropylene glycol. Additional examples can be monoethylene glycol ethers and acetates, diethylene glycol ethers and acetates, triethylene glycol ethers and acetates, and the like.

Examples of alcohols which can be linked to the thiophene ring through the oxygen atom include hexyl cellosolve, Dowanol PnB, ethyl carbitol, Dowanol DPnB, phenyl carbitol, butyl cellosolve, butyl carbitol, Dowanol DPM, diisobutyl carbinol, 2- ethylhexyl alcohol, methyl isobutyl carbinol, Dowanol Eph, Dowanol PnP, Dowanol PPh, propyl carbitol, hexyl carbitol, 2-ethylhexyl carbitol, Dowanol DPnP, Dowanol TPM, methyl carbitol, Dowanol TPnB. Trade names are well known in this art. See for example DOW P-series and E-series glycol ethers. The structure shown in (I) can stand alone as a polymer or it can be part of a block copolymer with another segment.

In some embodiments, the conjugated polymer is a 3 -substituted regioregular polythiophene having an alkyleneoxy type side chain.

The conjugated polymer can be present in an amount ranging from about 0.1 wt. % to about 90.0 wt. %. In an embodiment, about 10 wt. % to about 60 wt. % of the conjugated polymer can be present in the ink composition. In an illustrative embodiment, about 45 wt. % to about 55 wt. % of the conjugated polymer can be present in the ink composition. The amount of total solids in the conjugated polymer can be in an amount ranging from about 0.01 % to about 5.0 %. In an embodiment, the amount of total solids in the conjugated polymer is about 0.1% to about 1%. In an illustrative embodiment, the amount of total solids in the conjugated polymer is about 0.5% to about 0.8%.

Both ionic and non-ionic fluorosurfactant can be used in the present HTL compositions. In some embodiments the surfactant is a non-ionic polymeric fluorochemical surfactant. Non-limiting examples of suitable fluorosurfactants which can be added to the HTL materials include Novec^® FC 4430 (a fluorosurfactant commercially available from 3M located in St. Paul, Minn.), Novec^® FC 4432 (a non- ionic fluorosurfactant commercially available from 3M), Novec^® FC 4434 (a water- soluble non-ionic fluorosurfactant commercially available from 3M), BYK^®-340 (a polymeric fluorosurfactant commercially available from BYK), Zonyl^®. FSO (an ethoxylated non-ionic fluorosurfactant commercially available from Dupont located in Wilmington, Del.), Zonyl^®. FSA (a water soluble lithium carboxylate anionic fluorosurfactant commercially available from Dupont), Zonyl^®. FSN (a non-ionic fluorosurfactant commercially available from Dupont), Zonyl^®. FSP (a water-soluble, anionic phosphate fluorosurfactant commercially available from Dupont), Polyfox 136A (an anionic water dispersible fluorosurfactant commercially available from OMNOVA Solutions Inc., located in Chester, S.C.), Polyfox^®. 15 IN (a non-ionic water dispersible fluorosurfactant commercially available from OMNOVA Solutions Inc.), and Polyfox^®. 156A (an anionic water dispersible fluorosurfactant commercially available from OMNOVA Solutions Inc.). In illustrative embodiments, the fluorosurfactant is a perfluorobutanesulfonate, such as Novec^® FC 4430 or Novec^® FC 4432.

In some embodiments, the fluorosurfactant may be a non-ionic polymeric fluorochemical surfactant. In some embodiments, the fluorosurfactant may comprise perfluorobutane sulfonyl compounds including perfluorobutane sulfonates. In some embodiments, the fluorosurfactant may comprise a combination of fluoroaliphatic polymeric esters and polyether polymers. An example of such a fluorosurfactant is Novec^® FC 4432. In some embodiments, the fluorosurfactant may comprise a combination of 2-Propenoic Acid, 2-

[Methyl[(Nonafluorobutyl)Sulfonyl]Amino]Ethyl Ester, Telomer With Methyloxirane Polymer With Oxirane Di-2-Propenoate and Methyloxirane Polymer With Oxirane Mono-Propenoate; and a polyether polymers. An example of such a fluorosurfactant is Novec^® FC 4430.

The fluorosurfactant can be present in an amount ranging from about 0.01 wt. % to about 10.0 wt. %. In an embodiment, about 0.2 wt. % to about 5 wt. % of the fuorosurfactant can be present in the ink composition. In an illustrative embodiment, about 0.5 wt. % to about 3 wt. % of the fuorosurfactant can be present in the ink composition.

In some embodiments, the ink composition may further comprise one or more materials selected from matrix materials, conductors and additives.

In some embodiments, the ink composition additionally includes an organic polymer which is different from the conjugated polymer described above. This organic polymer can function as a matrix component or matrix material or planarizing agent which helps provide the needed properties, such as planarization for the hole injection layer. The matrix component, including planarizing agents, when blended with the hole injection component, will facilitate the formation of the HTL layer in a device such as an OLED or PV device. It will also be soluble in the solvent that is used to apply the HTL system. The planarizing agent may be comprised of, for example, a polymer or oligomer such as an organic polymer such as poly(4-vinyl phenol), poly(styrene) or poly(styrene) derivatives, poly(vinyl acetate) or its derivatives, poly( vinyl alcohol), including poly(vinyl alcohol) which is 88% hydrolyzed, poly(ethylene glycol) or its derivatives, poly(ethylene-co-vinyl acetate), poly(pyrrolidone) or its derivatives (e.g., poly(l-vinylpyrrolidone-co-vinyl acetate)), poly(vinyl pyridine) or its derivatives, poly(methyl methacrylate) or its derivatives, poly(butyl acrylate) or its derivatives, and combinations thereof.. More generally, it can be comprised of polymers or oligomers built from monomers such as CH₂CH Ar, where Ar = any aryl or functionalized aryl group, isocyanates, ethylene oxides, conjugated dienes, CH₂CHRiR (where Ri = alkyl, aryl, or alkyl/aryl functionalities and R = H, alkyl, CI, Br, F, OH, ester, acid, or ether), lactam, lactone, siloxanes, and ATRP macroinitiators.

In addition to facilitating the providing of a smooth surface to the HTL layer, the matrix component or planarization agent can also provide other useful functions such as resistivity control and transparency control. Planarity can be determined by methods known in the art including AFM measurements.

The matrix material can be present in an amount ranging from about 0.001 wt. % to about 10 wt. %. In an embodiment, about 0.05 wt. % to about 3 wt. % of the matrix material is present in the ink composition. In an illustrative embodiment, about 0.1 wt. % to about 2 wt. % of the matrix material is present in the ink composition.

In one aspect, an ink formulation for hole transport layer application is provided, the formulation comprising: about 45% to about 55% by weight of a 3- substituted regioregular polythiophene having an alkyleneoxy type side chain; about 0.1%) to about 2%> by weight of an organic polymer; about 2.5% to about 3.5% by weight of one or more fluorosurfactant. In some embodiments, the formulation further includes an organic solvent; and water.

Additionally, water soluble resins and aqueous dispersions can be used.

Aqueous dispersions can be for example poly(styrene sulfonic acid) (i.e. PSS dispersion), Nation dispersion (e.g., sulfonated fluorinated polymers), latex, and polyurethane dispersions. Examples of water soluble polymers include

polyvinylpyrollidinone and polyvinylalcohol. Other examples of resins include cellulose acetate resins (CA, CAB, CAP - Eastman). The solvent system used in the preparation of HTL inks can be adapted for use and processing with other layers in the device such as the anode or light emitting layer. Aqueous and non-aqueous solvent systems can be used.

Different solvents can be used in the current solvent system. Typically, the solvents used are organic non-polar solvents. More typically, the solvents used are aprotic non-polar solvents. Use of aprotic non-polar solvents can provide, in at least some examples, the additional benefit of increased life-times of devices with emitter technologies which are sensitive to protons. Examples of such devices include PHOLEDs.

In some embodiments, the solvent system, or solvents for dispersing components of the HTL ink composition can be a mixture of water and an organic solvent, including water miscible solvents, and solvents that comprise oxygen, carbon, and hydrogen, such as for example an alcohol or an etheric alcohol. Additional examples of water miscible solvents include alcohols such as isopropanol, ethanol, and methanol, and ethylene glycols and propylene glycols from Dow Chemical and Eastman Chemical. See for example Cellosolve, Carbitol, propane diol, methyl carbitol, butyl cellosolve, Dowanol PM. In some embodiments, the amount of water can be greater than the amount of organic solvent. A wide variety of combination of solvents can be used including non-aqueous including alcohols and other polar solvents. The composition can comprise a first solvent and a second solvent, different than the first solvent. In some embodiments, the first solvent can be an organic solvent and the second solvent can be water. In some embodiments, the first solvent can be an ethylene glycol and the second solvent can be water. These two solvents can be mixed in a wide variety of ratios adapted for a particular application. In some cases, one can eliminate or substantially eliminate the first solvent, or eliminate or substantially eliminate the second solvent. The relative amount (by weight or volume) of the first solvent to second solvent can range from for example 100 parts first solvent and 0 parts second solvent, to 0 parts first solvent and 100 parts second solvent, or 90 parts first solvent and 10 parts second solvent, to 10 parts first solvent and 90 parts second solvent, 80 parts first solvent and 20 parts second solvent, to 20 parts first solvent and 80 parts second solvent, 30 parts first solvent and 70 parts second solvent, to 70 parts first solvent and 30 parts second solvent, 60 parts first solvent and 40 parts second solvent, to 40 parts first solvent and 60 parts second solvent. Alternatively, it may be useful to select more than one solvent to use in the solvent system. The one or more solvents can be used in varying proportions to improve the ink characteristics such as substrate wettability, ease of solvent removal, viscosity, surface tension, and jettability.

Higher efficiencies were observed in inverted devices with HTL compositions comprising fluorosurfactants compared to those having other surfactants or no surfactants.

HTL INK PREPARATION

To form the HTL ink, one or more solvents and components are mixed. The components may comprise hole transport materials such as one or more of a conjugated polymer, a matrix material, resins, aqueous dispersions, dyes, coating aids, carbon nanotubes, nanowires, conductive inks, charge transport materials,

crosslinking agents and a fiuorosurfactant, or combinations thereof. Upon mixing, the components are dissolved in the solvent or mixture of solvents. For example, the dissolved components may comprise one or more conjugated polymer and fluorinated surfactant. The ink composition may be used to form the HTL of an electronic device, such as a photovoltaic device, for example an OPV or an inverted-OPV.

The solvent may be preheated before adding the components. The ink may be heated upon adding the components. The conjugated polymer may be dissolved in a first portion of the solvent, while the fluorinated surfactant may be dissolved in a second portion of the solvent. In some embodiments, the first and second portions may include different solvents or mixtures thereof. Subsequently, the first portion and second portions may be combined, such as mixed together. The resulting HTL composition may be photocurable.

In another aspect, also provided is a method of making a HTL ink composition comprising: (A) providing a first solvent, (B) providing a conjugated polymer, (C) providing an organic polymer different from (B), (D) providing a fiuorosurfactant, (E) providing a second solvent, and (F) combining in any order (A), (B), (C), (D) and (E) to form an ink composition.

The composition can comprise water and a water-miscible solvent. In some embodiments, the conjugated polymer can be a sulfonated regioregular polythiophene. In some embodiments, the conjugated polymer can be a 3 -substituted regioregular polythiophene, having an alkyleneoxy type side chain. The fluorosurfactant and organic polymer can be as described herein.

In some embodiments, preparation of HTL compositions include mixing a solvent, such as for example an organic solvent with an organic polymer, one or more additives including water soluble resins, aqueous dispersions and one or more fluorosurfactants, a conjugated polymer and optionally water. The various

components can be mixed together or added in stages and mixed at each stage to ensure the formation of a homogeneous mixture. The mixing can be achieved by standard methods such as by sonicating, agitation, or shear.

The composition comprising the conjugated polymer, the fluorosurfactant and solvent can be cast and annealed as a film on a substrate optionally containing an electrode or additional layers used to improve electronic properties of the final device. The films may be intractable to an organic solvent, which can be the solvent in the ink for subsequently coated or deposited layers during fabrication of a device. The films may be intractable to toluene or isopropyl alcohol, which can be the solvent in the ink for subsequently coated or deposited layers during fabrication of a device.

Film formation can be carried out by methods known in the art including for example spin casting, dip casting, dip coating, slot-die coating, ink jet printing, gravure coating, doctor blading, and any other methods known in the art for fabrication of, for example, organic electronic devices.

DEVICE PREPARATION AND MATERIALS

Devices can be made comprising one or more layers comprising the

compositions described herein and one or more electrodes, including anode and cathode. Layers can be built up on a substrate. See, for example, Chen et al,

Advanced Materials, 2009, 21, 1-16.

Various stages in the formation of a standard OPV device, similar in structure as the device of Fig. 1, includes, depositing a first electrode, which can be an anode such as an ITO, and a HTL, which comprises compositions described herein, sequentially on to the substrate. This is followed by depositing an active ink comprising for example a polythiophene, for example, P3HT, and a fullerene derivative, for example, PCBM or indene-fullerene, and a solvent, over the HTL.

During a spin coating deposition process, the active ink begins to dry as solvent evaporates from the solution thereby forming intermediate layer. Upon further drying, intermediate layer may form a bulk heterojunction which comprises acceptor and donor. More accurately the intermediate layer forms the interpenetrating network of spatially distributed and large interfaces between the donor and acceptor as bulk heterojunction active layer materials. A second electrode, which may be a cathode can be deposited over active layer by thermally depositing low work function metals such as Ca and Al.

Method of forming an inverted OPV device as shown in Fig. 2 follows a different sequence of processing steps. The stages include depositing a first electrode, which can be a cathode such as ITO or LR15, on to the substrate. This is followed by deposition of an hole blocking layer such as ZnO over the first electrode. The active ink comprising for example a p-type material, an n-type material, and a solvent, can then be deposited over the HBL. During a spin coating deposition process, the active ink begins to dry as solvent evaporates from the solution thereby forming

intermediate layer. Upon further drying, intermediate layer may form a bulk heterojunction which comprises acceptor and donor. More accurately the

intermediate layer forms the interpenetrating network of spatially distributed and large interfaces between the donor and acceptor as bulk heterojunction active layer materials. A HTL, which includes compositions described herein, is then deposited over the active layer. A second electrode, which may be an anode can be deposited over active layer by thermally depositing a high work function metal such as Ag.

In one aspect a method of forming an inverted photovoltaic device is provided, the method comprising forming a first electrode on a substrate; forming an hole blocking layer on the first electrode; forming an active layer on the hole blocking layer; forming a hole transport layer on the active layer; and forming a second electrode on the hole transport layer; wherein the hole transport layer comprises at least one conjugated polymer and a fluorosurfactant.

In some embodiments, the first electrode can be a cathode and the second electrode can be an anode. Devices using the presently claimed inventions can be made using, for example, ITO as a cathode material on a substrate. Other anode materials can include, for example, metals, such as Au, carbon nanotubes, single or multiwalled, commercially available materials such as LR15 (CP Films) and other transparent conducting oxides. The resistivity of the anode can be maintained below, for example, 15 Ω/sq or less, 25 or less, 50 or less, or 100 or less, or 200 or less, or 250 or less. The substrate can be rigid or flexible and can be, for example, glass, plastics (PTFE, polysiloxanes, thermoplastics, PET, PEN and the like), metals (Al, Au, Ag), metal foils, metal oxides, (TiOx, ZnOx) and semiconductors, such as Si. The ITO on the substrate can be cleaned using techniques known in the art prior to device layer deposition.

In case of inverse solar cell, a variety of layers can be included between the cathode and the active layer of a solar cell or the emissive layer of an OLED. These layers are generally referred to as hole transport layer (HTL), hole injection layers (HIL), hole collection (HCL), electron blocking layers (EBL) and/or interlayers.

In some embodiments, the first electrode can be a cathode and the second electrode can be an anode.

The active layer can comprise for example p-type and n-type materials, which function as donor molecules and acceptor molecules. The active layer can comprise organic compound including low molecular weight compounds, polymers, or a combination thereof.

The use of organic materials offers several desirable properties, for example, increased efficiency of the device; ease of processability of materials and components during device fabrication; the ability to use spin casting, drop casting, and printing techniques to apply different layers in the devices; the ability to prepare flexible devices; the ability to prepare low-weight devices; and the ability to prepare low-cost devices.

Organic conducting or conjugated polymers can be used in the active layer. For example, regioregular polymers such as polythiophenes can be used. See for example U.S. Pat. Nos. 6,602,974 and 6,166,172 to McCullough et al, and U.S.

Patent Application Pub. No. 2006/0076050 to Williams et al. See also U.S.

Provisional Patent Application Ser. No. 60/776,213 to Laird et al. filed Feb. 24, 2006 (High Performance Polymer Photovoltaics) and U.S. Patent Application Ser. No.

11/376,550 to Williams et al. filed Mar. 16, 2006 (Copolymers of Soluble

Polythiophenes with Improved Electronics Performance). See also materials available from Plextronics (Pittsburgh, Pa.).

Materials like fullerenes can be also used in the form of blends of conducting polymer and soluble fullerene derivative like PCBM (Phenyl C_n Butyric Acid Methyl Ester) or indene-fullerene. See for example U.S. Patent Application Ser. No.

11/743,587 to Laird et al. filed May 2, 2007 and also U.S. Provisional Patent

Application Ser. No. 60/812,961 to Laird et al. filed Jun. 13, 2006, Active layer thickness can be, for example, about 50 nm to about 250 nm, including for an OPV device.

The active layer can be formulated from a mixture of n-type and p-type materials. The n- and p-type materials can be mixed in a ratio of for example from about 0.1 to 4.0 (p-type) to about 1 (n-type) based on a weight, or from about 1.1 to about 3.0 (p-type) to about 1 (n-type) or from about 1.1 to about 1.5 (p-type) to about 1 (n-type). The amount of each type of material or the ratio between the two types of components can be varied for the particular application.

The active layer can be then deposited by spin casting, slot die, ink jetting, doctor blading, spray casting, dip coating, vapor depositing, or any other known deposition method, on top of, for example, the HTL film or the hole blocking layer. The film is then optionally thermally annealed at, for example, about 40 to about 250°C, or from about 150 to 180°C, for about 10 min to an hour in an inert atmosphere. Solvent annealing can be also carried out as needed. Combination of thermal and solvent annealing can be carried out. For other solar cell devices, like inverted structures by way of example, the order of layers can be adapted as known in the art. For example, an active layer can be deposited on a cathode.

A cathode layer can be added to the device, generally using for example thermal evaporation of one or more metals. For example, a 1 to 15 nm Ca layer is thermally evaporated onto the active layer through a shadow mask, followed by deposition of a 10 to 300 nm Al layer. In other embodiments, only the Al layer can be vapor deposition on to the HTL layer. In case of an inverse type devise, a 25 to 200 nm layer of a high work-function metal, such as Ag, can be vapor deposited on to the HTL layer.

The HTLs can be formed as films from compositions described herein.

HTLs can be added using, for example, spin casting, ink jetting, doctor blading, spray casting, dip coating, vapor depositing, or any other known deposition method. The HTL layer can be thermally annealed at a suitable temperature, such as about 100 to about 200°C for about 20 to 40 minutes in an antechamber at 200 mBar. The cycle can be repeated twice or more as required.

The thickness of the HTL layer can be for example from about 10 nm to about 300 nm thick, or from 30 nm to 60 nm, 60 nm to 100 nm, or 100 nm to 200 nm. The film then can be optionally dried/annealed at 110 to 200°C for 1 min to an hour, optionally in an inert atmosphere. A variety of layers can be included between the anode and the active layer of a solar cell or the emissive layer of an OLED. These layers are generally referred to as electron transport layers (ETL), electron injection layers (EIL), hole blocking layers (HBL) and/or interlayers.

In some embodiments, an optional interlayer may be included between the active layer and the cathode, and/or between the HTL or HIL and the active layer. This interlayer can be, for example, from 0.5 nm to about 100 nm, or from about 1 to 3 nm, thick. The interlayer can comprise an electron conditioning, a hole blocking, or an extraction material, such as LiF, BCP, bathocuprine, fullerenes or fullerene derivatives, such as C60, C70, C84 and other fullerenes and fullerene derivatives discussed herein.

Hole blocking layers can be used in, for example, solar cell devices. See, for example, US patent application no. 61/116,963 filed November 21, 2008.

The devices can be then encapsulated using a glass cover slip sealed with a curable glue, or in other epoxy or plastic coatings. Cavity glass with a

getter/desiccant may also be used, as well as a thermal melt adhesive, PSA, or other adhesive to a plastic or metal foil.

In addition, the active layer can comprise additional ingredients including for example surfactants, dispersants, oxygen and water scavengers.

The active layer can comprise multiple layers or be multi-layered.

The active layer composition can be formed from an ink comprising a mixture as a film. Films and devices can be annealed before use and testing. Thermal annealing and solvent annealing can be carried out.

In one aspect, an inverted solar cell with a HTL comprising a fluorosurfactant is provided. The organic solar cell comprises a substrate such as a glass substrate, a transparent conducting electrode such as ITO formed on the substrate, an n-type semiconductor hole blocking layer such as Ti02, ZnO, or CS₂CO₃ formed on the transparent electrode, a active layer formed over the hole blocking layer comprising a polymer blend with a fullerene derivative such as PLEXCORE PV2000 (Plextronics, Inc., Pittsburgh, PA), a hole transport layer which include compositions described herein, formed over the active layer, and a metal electrode such as Ag, or pristine Ag, formed over the hole transport layer.

In another embodiment, a method of making a device comprises using an HTL ink composition comprising a fluorosurfactant as described herein as part of an HTL layer in an OLED, an LED, an OPV, a photovoltaic device, an ESD, a SMOLED, a PLED, a sensor, a supercapacitor, a battery, a cation transducer, a drug release device, an electrochromic device, a transistor, a field effect transistor, an electrode modifier, an electrode modifier for an organic field transistor, an actuator, or a transparent electrode.

The compositions, devices, methods of making, and methods of using of the present embodiments provide an enhancement over conventional HTL compositions and in their use in electronic devices for example, in an OPV device. More specifically, the present embodiments provides a new solar cell, in some embodiments a new inverted-type solar cell, wherein the HTL compositions comprises a

f uorosurfactant.

ACTIVE LAYER P-TYPE MATERIAL

The active layer can comprise at least one p-type material. The p-type material can be an organic material including a polymeric material, although other types of p-type material are known in the art. For example, the p-type material can comprise a conjugated polymer or a conducting polymer, comprising a polymer backbone having a series of conjugated double bonds. It can be a homopolymer or a copolymer including a block copolymer or a random copolymer, or a terpolymer. Examples include polythiophene, polypyrrole, polyaniline, polyfluorene,

polyphenylene, polyphenylene vinylene, and derivatives, copolymers, and mixtures thereof. The p-type material can comprise a conjugated polymer soluble or dispersible in organic solvent or water. Conjugated polymers are described in for example T. A. Skotheim, Handbook of Conducting Polymers, 3^rd Ed. (two vol), 2007; Meijer et al, Materials Science and Engineering, 32 (2001), 1-40; and Kim, Pure Appl. Chem., 74, 11, 2031-2044, 2002. The p-type active material can comprise a member of a family of similar polymers which have a common polymer backbone but are different in the derivatized side groups to tailor the properties of the polymer. For example, a polythiophene can be derivatized with alkyl side groups including methyl, ethyl, hexyl, dodecyl, and the like.

One embodiment comprises copolymers and block copolymers which comprise, for example, a combination of conjugated and non-conjugated polymer segments, or a combination of a first type of conjugated segment and a second type of conjugated segment. For example, these can be represented by AB or ABA or BAB systems wherein, for example, one block such as A is a conjugated block and another block such as B is an non-conjugated block or an insulating block. Or alternately, each block A and B can be conjugated. The non-conjugated or insulating block can be for example an organic polymer block, an inorganic polymer block, or a hybrid organic-inorganic polymer block including for example addition polymer block or condensation polymer block including for example thermoplastic types of polymers, polyolefms, polysilanes, polyesters, PET, and the like. Block copolymers are described in, for example, US Patent No. 6,602,974 to McCuUough et al, and US Patent Publication No. 2006/0278867 to McCuUough et al. published December 14, 2006, each incorporated herein by reference in its entirety.

In particular, polythiophenes and derivatives thereof are known in the art. They can be homopolymers or copolymers, including block copolymers. They can be soluble or dispersible. They can be regioregular. In particular, alkoxy- and alkyl- substituted polythiophenes can be used. In particular, regioregular polythiophenes can be used as described in for example US Patent No. 6,602,974 and 6,166,172 to McCuUough et al, as well as McCuUough, R. D.; Tristram-Nagle, S.; Williams, S. P.; Lowe, R. D.; Jayaraman, M. J. Am. Chem. Soc. 1993, 115, 4910, including homopolymers and block copolymers. See also Plextronics (Pittsburgh, PA) commercial products. Soluble alkyl- and alkoxy-substituted polymers and

copolymers can be used including poly(3-hexylthiophene). Other examples can be found in US Patent Nos. 5,294,372 and 5,401,537 to Kochem et al. US Patent Nos. 6,454,880 and 5,331,183 further describe active layers.

Soluble materials or well dispersed materials can be used in the stack to facilitate processing.

Additional examples of p-type materials and polythiophenes can be found in WO 2007/011739 (Gaudiana et al.) which describes polymers having monomers which are, for example, substituted cyclopentadithiophene moieties, and which is hereby incorporated by reference in its entirety including formulas.

ACTIVE LAYER N-TYPE MATERIALS

The active layer composition in, for example, a solar cell may include an n- type component or electron acceptor, or an electron acceptor moiety. These can be materials with a strong electron affinity and good electron accepting character. The n- type component should provide fast transfer, good stability, and good processability. The n-type material is desirably soluble in, dispersible in, or otherwise miscible with the solvents in order to provide for solution processing. The n-type component may take the form of particles, including microparticles and nanoparticles, inorganic particles, organic particles, and/or semiconductor particles.

For example, the active layer can comprise an n-type material comprising at least one fullerene structure. Fullerenes are known in the art. Fullerenes can be described as spheroidal carbon compounds. For example, the fullerene surface can present [6,6] bonding and [6,5] bonding as known in the art. The fullerene can have a surface comprising six-membered and five-membered rings. Fullerenes can be for example C60, C70, or C84, and additional carbon atoms can be added via derivative groups. See for example Hirsch, A.; Brettreich, M., Fullerenes: Chemistry and Reactions, Wiley- VCH Verlag, Weinheim, 2005, which is hereby incorporated by reference including teachings for fullerene nomenclature and synthesis, derivatization, reduction reactions (Chapter 2), nucleophilic additions (Chapter 3), cycloadditions (Chapter 4), hydrogenation (Chapter 5), radical additions (Chapter 6), transition metal complex formation (Chapter 7), oxidation and reactions with electrophiles (Chapter 8), halogenation (Chapter 9), regiochemistry (Chapter 10), cluster modification (Chapter 11), heterofullerenes (Chapter 12), and higher fullerenes (Chapter 13). Methods described herein can be used to synthesize fullerene derivatives and adducts.

In particular, the active layer can comprise at least one n-type material, wherein the n-type material comprises at least one derivatized fullerene or fullerene derivative. The derivative compound can be, for example, an adduct. The terms "derivatized fullerene," "fullerene derivative" as used herein, can be used

interchangeably and can be, for example, fullerenes comprising, from 1 to 84, or 1 to 70, or 1 to 60, from 1 to 20, from 1 to 18, from one to ten, or from one to six, or from one to five, or from one to three substituents each covalently bonded to, for example, one or two carbons in the spheroidal carbon compounds. The derivatized fullerene can comprise a fullerene covalently bonded by [4+2] cycloaddition to at least one derivative moiety, R.

An example of an n-type material is PCBM.

One example of a fullerene derivative is an indene derivative, such as indene- fullerene. In addition, indene itself can be derivatized. Fullerene can be derivatized by methods described in for example Belik et al., Angew. Chem. Int. Ed. Engl., 1993, 32, No. 1, pages 78-80, which is hereby incorporated by reference. This paper describes addition to electron poor superalkene, C60, which can add radicals such as o-quinodimethane. It can be prepared in situ containing different functional groups and form very reactive dienes that can form [4 + 2] cycloadducts even with the least reactive dienophiles. This method provides good selectivity and stability.

Examples of n-type materials are described in, for example, International Patent Publication No. WO/2008/018931 published on February 14, 2008 and US Patent Publication 2008/0319207 published December 25, 2008, both to Laird, et al.

DEVICE TESTING

Known solar cell parameters can be measured including for example Jsc (mA/cm ) and V_oc (V) and fill factor (FF) and power conversion efficiency (%, PCE) by methods known in the art. See for example Hoppe article cited above and references cited therein.

Oriel Solar Simulators can be used to determine PV properties including for example FF, J_sc, V_oc, and efficiencies. The simulator can be calibrated by methods known in the art including for example calibration with a KG5-Si reference cell. External quantum efficiency (EQE) can be measured.

Other properties for the inks, films, and devices can be measured by methods known in the art.

Depending upon the conditions under which it is tested, the power conversion efficiency (PCE) can be, for example, at least about 1%, or at least about 2%, or at least about 3%, or at least about 4%, or at least about 5%, or at least about 6%, or at least about 7%, or at least about 8%, or higher.

Fill factor, which can be expressed as a number between 0 and 1 , or a percentage between 0 and 100%, can be, for example, at least about 0.1 (10%>), or at least about 0.2 (20%), at least about 0.3 (30%), or at least about 0.4 (40%), or at least about 0.5 (50%), or higher.

Open circuit voltage (V_oc) in V can be, for example, at least about 0.3, or at least about 0.4, or at least about 0.5, or at least about 0.6 V, or higher.

Short circuit current (J_sc) can be, for example, at least about 0.5, or at least about 0.6, or at least about 0.7, or at least about 0.8, or at least about 0.9, or at least about 1.0, or at least about 2.0, or at least about 3.0, or at least about 4.0, or at least about 5.0, or higher (mA cm ). While embodiments of the present invention may have been described with respect to formation of an inverted solar cell, the invention is not so limited.

WORKING EXAMPLES

Working Example 1 :

Exemplary compositions, for example, ink compositions of the present embodiments were prepared according to procedures below as follows:

General procedure 1 A: Preparation of the HTL Ink Composition.

A solution of a suitable matrix material (organic polymer) in an organic solvent was stirred at room temperature until the polymer was visually dissolved. Additives, including the fluorosurfactant and dispersants were then added to the solution and stirred until the solution was homogeneous. A suitable amount of conjugated polymer was dissolved in water and added to the homogeneous solution. The combined solutions were mixed again to ensure homogeneity. If required, additional amount of water was added and the solution was mixed at high energy overnight. The solution was filtered to remove any insoluble impurities.

Composition A (With fluorosurfactant)

Composition A was prepared by dissolving 15.8 g of P4VPhOH in 365 g of butyl cellosolve. Then 6 g of Nafion solution (purchased from Sigma Aldrich) l .lg of PSS (polystyrene sulfonate, purchased from Sigma Aldrich) and 74 g of water were weighed and mixed together. 507.5 g of the conjugated polymer (intrinsically conductive polymer, ICP) dispersion (0.67 % solids) was added and mixed well. 30.0 g of a 20% fluorosurfactant solution in butyl cellosolve was added to the solution and mixed together for 30 minutes.

Composition B (Without fluorosurfactant)

Composition B was prepared in an identical manner to Composition A by eliminating the fluorosurfactant.

Films were made with these HTL Compositions using spin coating process as follows: About 2 ml of the HIL solution were injected through a 0.45 mu PVDF membrane filter onto a UV/ozonized glass plate. The glass plate was spun initially at 350 rpm for 3 seconds and then 1600 rpm for 1 minute. The glass plate coated with HIL was then transferred to a 170°C hot plate.

Working Example 2: Device Fabrication

The device fabrication described below is intended as an example and does not in any way imply the limitation to the said fabrication process, device architecture (sequence, number of layers etc.) or materials.

The devices described herein were fabricated on indium tin oxide (ITO) surfaces deposited on glass substrates. The ITO surface was pre-patterned to define the pixel area of 0.05 cm . The device substrates were cleaned by ultrasonication in a dilute soap solution for about 20 minutes each followed by distilled water washes. This was followed by ultrasonication in isopropanol for about 20 minutes. The substrates were dried under nitrogen flow, following which they were treated in a UV- Ozone chamber operating at 300 W for 20 minutes.

The cleaned substrates were then coated with an HBL ink (for e.g. ZnO) and dried at 150 °C for about 39 minutes to form an HBL layer. After annealing the ZnO layer, the substrate is subjected to spinning first with water and then with IP A and re- anneal at 150 °C for about 10 minutes, to remove any residual organics. Dry film thicknesses ranged from approximately 20 nm to 150 nm.

A active ink comprising a p-type and an n-type material was then coated on to the HBL. The active ink was prepared by dissolving the p-type and n-type material in a solvent, e.g., an organic solvent at a suitable temperature. The PV inks used for this study were PV1000 and PV2000 (Plextronics, Inc).

In one example, a hole transporting layer (HTL) comprising Composition A was then coated on top of the active layer. The HTL layer was thermally annealed at a temperature of about 100 °C to about 200 °C for about 20 to about 40 minutes. The cycle was repeated twice or more in the antechamber at about 200 m Bar. In another example, a hole transporting layer (HTL) comprising Composition B was coated on top of the active layer in a similar manner.

The coating process was done on a spin coater but can be similarly achieved with spray coating, ink-jetting, contact printing or any other deposition method capable of resulting in a film of the desired thickness.

The substrates were then transferred to a vacuum chamber where the remaining layers of the device stack were deposited by means of physical vapor deposition. In one embodiment, a Silver (Ag) cathode is vapor deposited on to the HTL layer. In this example, the cathode layer was prepared by the deposition of about 100 nm silver metal layer, at about 4 nm/sec) with the base pressure at 1 x 10-6 or less mbr.

The devices thus obtained were encapsulated with a glass cover slip to prevent exposure to ambient conditions by means of a UV-light curing epoxy resin cured at 80 W/cm UV exposure for 4 minutes. We also encapsulate with a thermal melt adhesive to a metal or plastic foil with a hot roll laminator

Working Example 3 : Device Testing

Power Conversion Efficiency Determinations

Devices prepared as described above were tested using an Oriel Solar

Simulator and the voltage was swept from reverse to forward bias. From the resulting current that was measured, the power conversion efficiency of each device was determined. Data for each device are summarized in Tables 1-3 as well as relevant processing parameters for each device.

The photovoltaic characteristics of devices under white light exposure (Air Mass 1.5 Global Filter) were measured using a system equipped with a Keithley 2400 source meter and an Oriel 300W Solar Simulator based on a Xe arc lamp with output intensity of 100 mW/cm (AM1.5G). The light intensity was set using an NREL- certified Si-KG5 silicon photodiode.

The power conversion efficiency of a solar cell is given as r|=(FFl JsclVoc)/Pin, where FF is the fill factor, Jsc is the current density at short circuit, Voc is the photovoltage at open circuit and Pin is the incident light power density.

The resulting device performance for the aforementioned devices is shown in the table below.

Table 1. Photovoltaic performance of single layer OPVs using different types of HTL

*A11 devices are inverted; PV 1000 used for active layer

As shown in the table above, the device comprising the Composition A hole transport layer which was formed of an exemplary composition of the present invention, unexpectedly exhibited an improved performance to a comparative device comprising no hole transport layer as well as to a comparative device comprising Composition A hole transport layer which does not contain any fluorosurfactant. Inverted PV 2000 devices using an exemplary composition of the present invention achieved efficiencies within 70% of standard devices as seen in Table 2

Table 2. Inverted devices tested with aperture mask in place

Devices in Exp 5086, Table 3, were exposed under Xenon light in Qsun chamber either at 85 °C, 70% RH (Qsun) or ambient conditions (light) over a period of 3 weeks. The decreases of efficiency for devices with fluoro surfactant were less than those without surfactant. These data indicated that the addition of this surfactant will not negatively affect the device performance under these testing conditions.

Table 3. Evaluation of Compositions A and B in devices

Claims

CLAIMS:

1. A device comprising:

a substrate;

at least one cathode;

at least one anode;

at least one active layer disposed between the cathode and anode;

at least one hole transport layer;

wherein the hole transport layer comprises a composition comprising:

(i) at least one hole transport material; and

(ii) at least one fluorosurfactant

2. The device of claim 1, wherein the hole transport layer is disposed between the active layer and the anode.

3. The device according to claim 1, wherein the hole transport material comprises a conjugated polymer.

4. The device according to claim 3, wherein the conjugated polymer is a regioregular polythiophene.

5. The device of claim 4, wherein the conjugated polymer is a 3-substituted regioregular polythiophene having an alkyleneoxy type side chain.

6. The device of claim 1, wherein the fluorosurfactant is a non-ionic polymeric fluorochemical surfactant.

7. The device of claim 6, wherein the fluorosurfactant is a perfluorobutane sulfonate fluorosurfactant.

8. The device according to claim 1, wherein the composition comprises between about 45% and 55 > by weight conjugated polymer and between about 0.1 %> and 5%> by weight fluorosurfactant.

9. The device according to claim 1, wherein the composition comprises between about 45% and 55% by weight conjugated polymer and between about 2.5% and 3.5%) by weight of fluorosurfactant.

10. The device according to claim 1,

wherein the device demonstrates an increase in power conversion efficiency of at least 20% compared to a substantially analogous device having a hole transport layer composition which does not include the fluorosurfactant.

11. The device according to claim 1 ,

wherein the device demonstrates an increase in power conversion efficiency of at least 50% compared to a substantially analogous device having a hole transport layer composition which does not include the fluorosurfactant.

12. The device according to claim 2, wherein the cathode comprises Ag.

13. The device according to claim 2, wherein the anode comprises indium tin oxide or LR15.

14. The device of claim 1, wherein the active layer comprises a composition comprising a donor molecule and an acceptor fullerene derivative.

15. The device of claim 14, wherein the donor molecule comprises polythiophene.

16. The device of claim 15, wherein the acceptor fullerene derivative comprises PCBM or indene-fullerene.

17. The device according to claim 1, wherein the hole transport layer has a thickness of about 20 nm to about 200 nm.

18. The device according to claim 1, wherein the substrate comprises glass, polyethylene terephthalate or polyethylene naphthalate.

19. An ink composition for forming the hole transport layer of an inverted photovoltaic device, the composition comprising hole transport materials and a fluorosurfactant.

20. The composition of claim 19, further comprising one or more solvents.

21. The composition of claim 20, wherein the solvent comprises a mixture of water and an organic solvent.

22. The composition of claim 21, wherein the organic solvent is butyl cellosolve.

23. The composition according to claim 19 , wherein the hole transport material comprises a conjugated polymer.

24. The composition of claim 23, wherein the conjugated polymer is a 3 -substituted regioregular polythiophene having an alkyleneoxy type side chain.

25. The composition of claim 19, wherein the fluorosurfactant is a non-ionic polymeric fluorochemical surfactant.

26. The composition of claim 25, wherein the fluorosurfactant is a perfluorobutane sulfonate fluorosurfactant.

27. The composition according to claim 19, wherein the composition comprises between about 45% and 55% by weight conjugated polymer and between about 0.1 % and 5%) by weight fluorosurfactant.

28. The composition according to claim 19, wherein the composition comprises between about 45% and 55% by weight conjugated polymer and between about 2.5% and 3.5%) by weight fluorosurfactant.

29. The composition according to claim 19, further comprising one or more materials selected from matrix materials, conductors and additives.

30. The composition according to claim 28, wherein the matrix material comprises an organic polymer.

31. The composition according to claim 29, wherein the organic polymer is poly(4- vinylphenol).

32. An ink formulation for hole transport layer application comprising:

about 45% to about 55% by weight of a 3 -substituted regioregular

polythiophene having an alkyleneoxy type side chain;

about 0.1%) to about 2% by weight of an organic polymer; and

about 2.5 % to about 3.5% by weight of one or more fluorosurfactant.

33. A device prepared from the composition according to claim 19.

34. The device of claim 33, wherein the device is an LED, an OLED, an OPV, an electrochromic device, a supercapicitor, a battery, an actuator, or a transistor.

35. The device of claim 33, wherein the device is an inverted solar cell.

36. A device prepared from the formulation according to claim 33.

37. A method of forming an inverted photovoltaic device comprising:

forming a first electrode on a substrate;

forming an hole blocking layer on the first electrode;

forming an active layer on the hole blocking layer;

forming a hole transport layer on the active layer; and

forming a second electrode on the hole transport layer;

wherein the hole transport layer comprises at least one conjugated polymer and a fluorosurfactant.

38. The method of claim 37, wherein the first electrode is a cathode.

39. The method of claim 38, wherein the second electrode is an anode.

40. The method claim 37, wherein the hole transport layer is formed by depositing an ink comprising:

at least one solvent and a plurality of dissolved components, the dissolved components comprising at least one conjugated polymer and a fluorosurfactant.

41. The method according to claim 40, wherein the ink comprises between about 45% and 55% by weight conjugated polymer and between about 0.1% and 5% by weight fluorosurfactant.

42. The method according to claim 40, wherein the ink comprises between about 45%) and 55% by weight conjugated polymer and between about 2.5% and 3.5% by weight fluorosurfactant.

43. The method according to claim 37, wherein the HTL layer is thermally annealed.

44. The method according to claim 43, wherein the HTL layer is thermally annealed at a temperature of about 100 °C to about 200 °C for about 20 to about 40 minutes.

45. A method of forming an ink usable for deposition as the hole transport layer of a photovoltaic device, the method comprising: (A) providing a first solvent, (B) providing a conjugated polymer, (C) providing an organic polymer different from (B), (D) providing a fluorosurfactant, (E) providing a second solvent, and (F) combining in any order (A), (B), (C), (D) and (E) to form an ink composition.