KR20080108475A - High performance polymer photovoltaics - Google Patents

Abstract

Compositions for use in solar cell active layers comprising regioregular polythiophene of relatively low molecular weight and n-type semiconductors. Narrow, low polydispersity is also important. Advantages include better efficiencies, better current density, more versatility, and better processability. Devices are fabricated including use of hole injection layers. Solvent selection, annealing, and molecular weight can be used to provide good performance. Fullerene derivatives can be used as n-type acceptors. ® KIPO & WIPO 2009

Description

High Performance Polymer Photovoltaic Cells {HIGH PERFORMANCE POLYMER PHOTOVOLTAICS}

There is an economic need for a practical source of renewable energy that will truly reduce the dependence on fossil fuels. Silicon-based solar energy systems have been a potential candidate for years. However, the capital-intensive nature of the silicon manufacturing process contributes to the cost structure, which lacks significant commercial success. Intrinsically conductive polymers (ICPs) (or conductive polymers or conjugated polymers such as polyacetylene, polythiophene or poly (phenylene vinylene)) represent great potential as significantly lower cost devices, which are conventional It is because it can handle like ink of a printing process. There is a need to promote solar cell performance with the commercialization of conductive polymer solar cells with a versatile technology platform.

Alternative energy sources, particularly renewable energy, are currently trying to dramatically change the functional and cost boundaries resulting from energy sources. This need is highlighted by the rapid increase in costs, environmental impact and the geopolitical implications of dependence on fossil fuels around the world. Provincial level regulations from the world (eg Kyoto) are increasing the demand for cost-effective renewable energy supply. Generating power using the sun's rays represents an attractive pollution-free renewable energy source.

For example: (1) handheld electronics manufacturer / consumer (solar technology of battery charging will reduce device weight and size and prolong usage time); (2) consumers in households (solar technology will reduce overall power consumption and can provide electricity to millions of generations currently inaccessible); And (3) many buyers, including government and industry (solar industry will reduce its dependence on fossil fuels and meet environmental objectives) can benefit from solar technology.

Silicon-based solar cells first demonstrated 50 years ago (Perlin, John "The Silicon Solar Cell Turns 50" NREL 2004)) are now the first technology in the 5 billion solar cell market. However, the installation cost of this technique is approximately 5 to 10 times the installation cost of a traditional power source. Thus, its cost / performance structure does not facilitate wide market adoption. As a result, solar energy accounts for less than 1% of the country's current energy supply. In order to expand this range and meet the growing need for renewable energy sources, new alternative technologies are needed.

Conductive polymers are an important component of new generation solar cells that promise to significantly reduce the cost / performance barriers of existing solar cells. The first advantage of the conductive polymer solar cell is that the core material and the device itself can be manufactured at low cost. Core materials similar to plastics are made in industrial scale reactors under standard thermal conditions. These may be solutions that are molded into thin films or may be solutions printed by standard printing techniques. Thus, the cost of the manufacturing plant is less expensive than the silicon manufacturing equipment. This creates a low total cost solar cell manufacturing platform. In addition, conductive polymer solar technology offers flexible, lightweight design advantages over silicon-based solar cells. This technology is very promising, but the obstacles of commercialization remain. Hopefully, there is a need to find a composition that substantially improves performance with minimal changes in composition.

Polythiophenes have been used in photovoltaic devices as high molecular weight materials and / or generally in a broad molecular weight distribution. For example, one reference describes a photovoltaic cell using polythiophene reported at a molecular weight of 87,000. Reyes-Reyes et al, Applied Physics Letters , 87, 083506 (2005). Other references describe photovoltaic cells using polythiophenes having a reported molecular weight of 21,100. Kim et al, Applied Physics Letters , 86, 063502, (2005). Other references describe photovoltaic cells using polythiophenes having a reported molecular weight of 100,000. See Yang et al., Nano Letters , 2005, vol. 5, no. 4, 579-583. Molecular weight and polydispersity are often not recognized as important parameters of impact performance, but in many cases higher molecular weights are taught, suggested, or indicated as desirable or necessary. See, eg, (1) Schilinsky, P. et al., Chem . Mater . 2005, 17 (8), 2175-2180; (2) Kline, R. et al., Macromolecules (2005), 38 (8), 3312-3319; (3) Nether, et al., Adv . Funct . Mater . 2004, 14, 757-794. In addition, fractionation is not a commercially attractive method of controlling molecular weight.

There is a need to better understand how to achieve high active layer PV performance in terms of polymer microstructure and morphology.

Summary of the Invention

One or more advantages of the present invention include improved photovoltaic performance, including current density and efficiency by controlled use of polymer chemistry. In addition, improved processing and versatility can be achieved.

In one embodiment, the present invention provides a composition comprising at least one regioregular polythiophene, at least one n-type semiconductor, having a number average molecular weight of about 9,000 or less as determined by gel permeation chromatography in chloroform.

In another embodiment, the invention provides a plurality of electrodes; And at least one active layer comprising at least one regioregular polythiophene having at least about 9,000 number of molecular weight and at least one n-type semiconductor as measured by gel permeation chromatography in chloroform.

In another embodiment, the present invention provides a composition comprising one or more regioregular polythiophenes having a number average molecular weight of about 9,000 or less as determined by gel permeation chromatography in chloroform; One or more n-type semiconductors; And one or more halogenated aromatic solvents.

In another embodiment, the present invention provides a composition comprising (i) at least one regioregular polythiophene having a number average molecular weight of about 9,000 or less as determined by gel permeation chromatography in chloroform; preparing a composition comprising (ii) at least one n-type semiconductor and (iii) at least one halogenated aromatic solvent; Removing the solvent to prepare a film comprising regioregular polythiophene and an n-type semiconductor; A method of forming a film is provided that includes annealing a film.

In a preferred embodiment to achieve the most desirable performance, the number average molecular weight is about 6,000 to 9,000 as measured by GPC in chloroform. In addition, the polythiophene may have a polydispersity of about 1.1 to about 1.5.

1 illustrates a typical conductive polymer photovoltaic (solar) cell.

2 shows the ground state (left) and exciton formation and dissociation (right) of the p / n junction. The excitons are bonded holes (+) and electrons (-). Arrows indicate dissociation of electrons into the n-type material and conduction of the device through the aluminum cathode. Holes (+) are conducted to the ITO anode. The energy generated is provided by the charge q times the open circuit voltage V _oc .

3 shows the current voltage curve of Example 1. FIG.

4 shows a current voltage curve of Example 2 (comparative).

5 shows the current voltage curve of Example 3. FIG.

All references mentioned herein are incorporated herein by reference.

Electrically conductive polymers, including polyacetylene, poly (p-phenylene), poly (p-phenylene sulfide), polypyrrole and polythiophene, are described in The Encyclopedia of Polymer Science and Engineering , Wiley, 1990, pages 298-300. This reference also describes the blending and copolymerization of polymers, including block copolymer formation.

In one embodiment, the present invention provides a composition comprising at least one regioregular polythiophene having a number average molecular weight of about 15,000 or less as determined by gel permeation chromatography, and at least one n-type semiconductor. This composition can be used as the active layer of a photovoltaic device.

Photovoltaic / solar cell device

Solar cells are generally described including some preferred embodiments. Traditional conductive polymer solar cells can include five components (see, eg, FIG. 1). Transparent electrodes such as indium tin oxide (ITO) coated on plastic or glass can function as the anode. The thickness can be about 100 nm, allowing light to enter the solar cell. The anode can be coated with a 100 nm hole injection layer (HIL). HIL may planarize the surface of the ITO and facilitate the collection of positive charge carriers (holes) from the light harvesting layer to the anode. The counter electrode or cathode may be made of a metal such as calcium or aluminum and is typically at least 70 nm thick, for example. This may include a thin conditioning layer (eg, less than 1 nm of lithium fluoride) that may increase lifetime and performance. In some cases, the negative electrode may be coated on a support surface, such as a flexible plastic or glass sheet. This electrode can carry electrons out of the solar cell and complete the electrical circuit.

There may be junctions of p-type and n-type semiconductors (about 100 nm thick) between these electrodes. P-type materials are often called light harvesting components. This material can absorb photons (light) that energize electrons from its "base" state to an excited energy state, leaving a positive charge or "hole". These electron-hole combinations combine together to form a so-called “exciton” (see, eg, FIG. 2).

The excitons diffuse into the junction between the p-type and n-type materials, where the charge can be separated. The electron and "hole" charges are then conducted to the electrode through the n-type and p-type materials, respectively, to create a flow of current out of the cell. The n-type component may include a material having strong electron affinity such as, for example, carbon fullerene, derivatives thereof, titanium dioxide, or cadmium selenide, as described in more detail below.

The shape of the p / n junction can be important for solar cell performance. The excitons can be formed and diffused in the p-type semiconductor. See, eg, Chirvase et al., Nanotechnology , 15 (2004) 1317-1323. However, they must reach the interface of the n-type and p-type materials, which can be separated before the charges relax back to the ground state or “canch” through other processes. The diffusion length of the excitons is in nanometers, so the ideal junction is a "bulk heterojunction" that is macroscopically interpenetrating, but microscopically has a linked phase-separation domain.

In the practice of various embodiments of the present invention, the following references may be used in addition to the references mentioned in the Background section: (1) Brabec, et al. Adv . Func . Mater. 2001, 11, 374-380; (2) Sariciftci, NS Curr . Opinion in Solid State and Materials Science , 1999, 4, 373-378; (3) Sariciftci, N. Materials Today 2004, 36; (4) Hoppe, H .; Sariciftci, NS J. Mater . Res. 2004, 19, 1924; (5) Nakamura et al., Applied Phsics Letters , 87, 132 105 (2005); (6) Paddinger et al., Advanced Functional Materials , 2003, 13, No. 1, January, 85; (7) Kim et al., Photovoltaic Materials and Phenomena Scell- 2004, 1371, (8) J. Mater . Res . , Vol. 20, No. 12, Dec. 2005, 3224; (9) Inoue et al., Mater . Res . Soc . Symp . Proc . , vol. 836, L. 3.2.1; (10) Li et al., J. Applied Physics , 98, 043704 (2005)].

Regioregular polythiophene

Regioregular polythiophenes are known in the art. These may be copolymers including homopolymers or block copolymers. Regioregular polythiophenes can include 3-substituted polythiophenes, including 3-alkyl or 3-alkoxy polythiophenes. The side groups can be substituted with heteroatoms including oxygen and sulfur. Regioregular polythiophenes may be soluble in organic solvents. The degree of regioregularity may be, for example, at least 85%, or at least 90%, or at least 95%, or at least 98%.

In particular, photovoltaic applications of these polythiophenes are described, for example, in US Provisional Application No. 60 / 661,9934 and Williams, filed March 16, 2005, to Williams et al., Which is incorporated herein by reference. 1,234,373, filed September 26, 2005, and the like.

In addition, synthetic methods, doping and polymer characterization, including regioregular polythiophenes with side groups, are described, for example, in US Pat. No. 6,602,974 (McCullough et al.) (Block copolymers and nanoparticles). Wire form) and US Pat. No. 6,166,172 (McCullough et al., Describing GRIM polymerization method). Additional techniques are described in the article "The Chemistry of Conducting Polythiophenes", by Richard D. McCullough, Adv . Mater . 1998, 10, No. 2, pages 93-116 and references cited therein. Other references available to those of skill in the art can be found in the Handbook , incorporated herein by reference. of Conducting Polymer , 2 ^nd Ed. 1998, Chapter 9, by McCullough et al., "Regioregular, Head-to-Tail Coupled Poly (3-alkylthiophene) and its Derivatives," pages 225-258. This reference is also described in chapter 29, "Electroluminescence in Counjugated Polymers" at pages 823-846, incorporated herein by reference. Additional references include McCullough, RD; Lowe, RS J. Chem . Soc , Chem . Commun. 1992, 70; McCullough, RD; Lowe, RD; Jayaraman, M .; Anderson, DL J. Org . Chem . 1993, 58, 904; Lowe, RS; Khersonsky, SM; McCullough, RD Adv . Mater . 1999, 11, 250; McCullough, R. d .; Tristram-Nagle, S .; Williams, SP; Lowe, RD; Jayaraman, M. J. Am . Chem . Soc . 1993, 115, 4910.

Polythiophenes are described, for example, in Roncali, J., Chem . Rev , 1992, 92, 711; Shopf et al., Polythiophenes : Electrically Conductive Polymers , Springer: Berlin, 1997.

Polymeric semiconductors are described, for example, in "Organic Transistor Semiconductors" by Katz et al., Accounts of Chemical Research , vol. 34, no. 5, 2001, page 359, pages 265-367.

Block copolymers are described, for example, in Block Copolymers , Overview and Critical Survey , by Noshay and McGrath, Academic Press, 1977. For example, this document describes AB diblock copolymers (Chapter 5), ABA triblock copolymers (Chapter 6) and-(AB) _n -multiblock copolymers (Chapter 7), which are described herein. It can form the basis of the block copolymer type.

Further block copolymers, including polythiophenes, are described, for example, in Francois et al, Synth . Met . 1995, 69, 463-466; Yang et al., Macromolecules 1993, 26, 1188-1190; Waiwski etl, Nature ( London ) , vol. 369, June 2, 1994, 387-389; Jenekhe et al., Science , 279, March 20, 1998, 1903-1907; Wang et al., J. Am . Chem ., Soc . 2000, 122, 6855-6861; Li et al., Macromolecules 1999, 32, 3034-3044; Hempenius et al., J. Am . Chem . Soc . 1998, 120, 2798-2804.

Molecular Weight

Polymer molecular weight and its gel permeation chromatography measurements are known in the art: see, eg, Billmeyer, Textbook of Polymer Science , 3 ^rd Ed., 1984, including chapter one; Allcock & Lampe, Contemporary polymer Chemistry , 1981 including chapters 14 and 15.

The one or more regioregular polythiophenes may have a number average rich amount of about 9,000 or less. The number average molecular weight can be, for example, about 1,000 to about 9,000, or about 2,500 to about 9,000, or about 6,000 to about 9,000, or about 7,000 to about 9,000. Molecular weights are measured as known to those skilled in the art using GPC and chloroform solvent by methods described in the examples or substantially similar to the examples. This provides a uniform way to compare the impact on PV performance.

If the regioregular polythiophene is a block copolymer comprising regioregular polythiophene segments and nonregioregular polythiophene segments, the weight average molecular weight refers to the weight of the regioregular polythiophene segments.

The molecular weight polydispersity can be narrowly adjusted to be, for example, about 1 to about 1.5, or about 1.1 to about 1.5. The lower the polydispersity, the more the charge mobility can be increased by strengthening the shape of the active layer. This can increase the curve factor and short circuit current.

Doping

Regioregular polythiophenes can be used without doping. The composition can be formulated without the addition of a dopant.

N-type semiconductor

The n-type component or electron acceptor is a material having strong electron affinity, good electron accepting characteristics, for example particles, particulates, nanoparticles, inorganic particles, organic particle semiconductor particles, carbon fullerenes, fullerene derivatives, soluble fullerenes, titanium dioxide Cadmium selenide, and perylene or perylene derivatives. The n-type semiconductor may be a molecular material, or a nonpolymeric material, having a molecular weight of less than about 2,000 g / mol or less than about 1,000 g / mol. The n-type component can be any component that provides a bulk heterogeneous junction with the regioregular polythiophene. PCBM is a preferred example, the structure of the PCBM is known in the art. n-type semiconductors should provide high speed transfer, good stability, good solubility and good processability.

N-type semiconductors of the fullerene and fullerene derivative types can be found in US Pat. Nos. 5,454,880 and 5,331,183 (Sariciftci et al.), Which is incorporated herein by reference. Other n-type semiconductors are described in the references mentioned herein.

Quantity of ingredients

Desirable photovoltaic effects can be achieved by controlling the weight ratio of regioregular polythiophene and n-type semiconductor. For example, the weight ratio can be about 4: 1 to about 0.5: 1, or about 3: 1 to about 0.5: 1, or about 2.5: 1 to about 1: 1. The amount can be adapted to one or more other variables such as, for example, molecular weight, solvent selection, casting or coating conditions, and annealing temperature and time.

Film forming / printing

Conventional methods can be used to convert the compositions into solid forms, including thin and printed forms. For example, the solid can be dissolved or dispersed in one or more solvents, including organic solvents, roll coated, screen printed, spin cast or ink jet printed, coated and printed by other known methods. Other methods are described in the references mentioned herein.

Solvents used in compound molding and film casting are, for example, organic solvents, aromatic solvents such as toluene or xylene, haloaromatic or halogenated aromatic solvents, chlorinated aromatic solvents, chlorinated solvents such as chlorobenzene, 1,2- Dichlorobenzene, chloroform or 1,2-dichloroethane). By varying the solids content of the solution or dispersion, the best PV properties and processing can be achieved. For example, the solids content can be about 20% to about 80%, or 30% to about 70%.

The film thickness can be, for example, about 10 to about 500 nm, or about 50 to about 250 nm, or about 100 to about 200 nm.

The film may optionally be thermally annealed. Annealing temperature and time can be adjusted to achieve the desired results. The annealing temperature may be, for example, about 100 to about 170 ° C, or about 105 to about 155 ° C. The annealing temperature may be below the melting point of the regioregular polythiophene. The annealing temperature can be, for example, lower than the glass transition temperature of the regioregular polythiophene, higher than the glass transition temperature, or higher than the glass transition temperature. The annealing temperature may be, for example, about 5 ° C. to about 60 ° C. above the glass transition temperature. The glass transition temperature and melting point can be influenced by the presence of the n-type semiconductor. For example, they can be lowered.

Device and characteristics

Once the active layer is prepared, the active layer properties can be measured by methods known in the art and described in the Examples below. These methods can include the measurement of current-voltage curves using a solar simulator. Device measurements can be performed at room temperature or 25 ° C. The material can optionally be encapsulated and, for example, stored under inert gas conditions.

For example, the open circuit voltage V _oc can be measured and can be, for example, about 0.55 V or more, or about 0.58 V or more, or 0.6 V or more.

The short circuit current I _sc can be measured and can be, for example, at least about 6 mA / cm 2, or at least about 7.7 mA / cm 2, or at least about 9 mA / cm 2, or at least about 12 mA / cm 2.

Fill factor (FF) can be measured and can be, for example, at least about 0.4, or at least about 0.56, or at least about 0.6.

The efficiency (E) can be measured and can be, for example, at least about 2.5%, or at least about 3%, or at least about 4%, or at least about 5%. The efficiency can be measured under 100 mV / cm 2.

It is possible to produce known PV device structures, including devices comprising a plurality of active layers. The device may comprise a plurality of active layers, including stacked active layers.

Solar cell devices are described, for example, in Dennler and Sariciftci, Proceedings of the IEEE, vol. 93, no. 8, August 2005, pages 1429-1439; US Pat. No. 6,812,399, and 6,933,436.

Method of Preparation of the Composition

One aspect is the preparation of a composition comprising a solventborne coating composition and a dry coating composition. For example, regioregular polythiophenes can be synthesized including tablets, and the controlled number average molecular weight is for example less than 9,000, or from 6,000 to 9,000. The regioregular polythiophene can then be blended well with an n-type semiconductor such as a fullerene derivative. Films or coatings can be prepared by removing the solvent. Doping can be adjusted as the case may be.

Further description is provided using non-limiting examples. P3HT is poly (3-hexylthiophene) and is regioregular unless otherwise indicated. PCBM is a fullerene derivative, which is 1- (3-methoxycarbonyl) -propyl-1-phenyl- (6,6) C ₆₁ . PEDOT is poly (3,4-ethylenedioxythiophene). PSS is poly (styrenesulfonate).

P3HT: PCBM-based organic photovoltaic cells are described as device structure ITO / PEDOT: PSS / [P3HT: PCBM] Ca / Al, where low MW P3HT (8k) functions substantially better than high MW P3HT (19k). appear. In addition, the polydispersity of low MW P3HT is 1.4.

Active layer fabrication, deposition and device fabrication:

Material: Two P3HT polymers were used in the present invention and were synthesized by the GRIM method. Two different molecular weight polymers (M _n = 8k and 19k) were prepared. Molecular weight was determined by gel permeation chromatography (GPC). GPC traces of poly (3-hexylthiophene) were recorded on a Waters 717 separation autosampler equipped with a Waters 515 HPLC pump and a Waters 486 variable absorbance detector, where chloroform was the eluent (flow rate 1.0 mL). Per minute, 35 ° C., λ = 254 nm, and a series of three Styragel columns (10 ⁵ , 10 ³ , 100 Hz; Polymer Standard Services) and guard columns. Calibration based on polystyrene standards was applied to the determination of molecular weight and toluene was used as internal reference. GPC data was collected and processed using the Win GPC software package from Polymer Standard Services. Traces were analyzed by manual selection of UV absorbance versus elution volume at both ends of the peak (typically Gaussian), setting baseline absorbance to zero absorbance and processing the selected data using a Win GPC molecular weight algorithm.

Note on MW Naming: The two MWs of P3HT used in the present invention were determined to be 19k of 'high MW' and 8k of 'low MW' by this method, and this description was used throughout.

Note on MW Determination: The foregoing description of the MW determination method is an example of what is the correct method of MW determination of poly (3-alkylthiophenes). Polythiophenes aggregated at all dilution rates of various solvents, which are involved in molecular weight determination by size-exclusion chromatography (or GPC) as is known in the art. Aggregation of the PT polymer chains results in the formation of aggregates having a size larger than one isolated polymer, as known in the art. Polythiophenes are also characterized as "rod" polymers, and thus the correction of the GPC-crystal molecular weight for coiled polymers, which are polystyrene standards, is known in the art as the hydrodynamic volume of rod-to-coil polymer structures. The difference results in a shift in the experimentally determined MW value. These factors were determined by calibration for NMR and other MW determination techniques to result in GPC determined MW overestimated 1.5-2.0 times the actual MW of the analyzed polymer.

Because different solvents aggregate PT differently, GPC analysis of PT polymers in different solvents will show different MW values. This has been observed in previous efforts, while chloroform, a good solvent of P3HT, has been shown to provide 'lowest' M _n values, while THF has been observed to be more variable, with about 1.2 to 2.0 times the molecular weight determined from chloroform GPC analysis. M _n values were provided. Thus, chloroform is the solvent to be used.

There is no standardized approach in the literature regarding which solvent is best for use in comparative GPC analysis. THF is generally reported in GPC analysis, which means that the molecular weight reported in the literature is at best unparalleled and possibly overestimated. Molecular weights reported herein were determined using chloroform as eluent.

NMR measurement:

NMR determination of MW:

For comparison and certification, a full 500 MHz ¹ H NMR spectrum of regioregular P3HT was obtained. Two small triplets at d = 2.56-2.64 ppm result from rr-P3OHT at the H / H and H / Br ends, and generally have different strengths due to lot-lot changes in Br endcapping. They can be assigned to benzyl methylene at each two distinct terminal units and are integrated as one group. This allows for a relatively accurate determination of the molecular weight from the integration of end group resonances for large polymers. The DP _n of the aforementioned polymers can be calculated from the reported integral function and is equal to the ratio of the two triplets. The integral function of the large triplet of the polymer backbone is 2.031 arbitrary units (au), together with 0.056 au for the two smaller triplets. The calculation of the ratio of end group to main chain is 2.031 * 2 (the backbone of the 2H's-polymer) to 0.056 (two methylenes of the 4H's-terminal group), with 72 monomer units (MW = 166 g / mole of each repeating unit) _n = 14,000 (greater than 98% of HT). The molecular weight of the polymer was also measured by GPC using chloroform as the eluent (flow rate 1.0 mL / min, 35 ° C., l = 254 nm) and a correction based on polystyrene standards of molecular weight using toluene as the internal standard. The crystals were applied (M _n : 26900, PDI: 1.3). GPC is known to overestimate the MW of PAT by 1.5 to 2 fold, consistent with the NMR characterization above.

Active layer solution preparation: P3HT was first dissolved in 1,2-dichlorobenzene (DCB) to make a 30 mg / ml solution, then combined with PCBM in 50 wt% dichlorobenzene (purchased from ADS, used as received). The blend was stirred at 40 ° C. for 14 hours under anhydrous nitrogen atmosphere. The ratio of P3HT to PCBM was 2: 1.

Device Fabrication: Prior to device fabrication, the ITO-coated glass substrates were washed in order with sonication in detergent, deionized water, acetone and isopropyl alcohol. A thin layer (30 nm) of PEDOT / PSS (Baytron P VP AI 4083) was spin-coated to modify the ITO surface. The film was heated at 120 ° C. for 1 hour in a nitrogen-filled glove box (<2 ppm O ₂ and H ₂ O). The active layer was obtained by spin-coating the blend for 60 seconds at 600 rpm and the thickness of the film was about 150 nm as measured by a calibration surface roughness meter. The active device area was 0.09 cm 2. The film was thermally annealed at 110 ° C. for 10 minutes.

Polymeric PV devices were fabricated by spin-coating a blend of P3HT / PCBM in a 1: 1 weight ratio, sandwiched between a transparent anode and a cathode. The anode consisted of a glass substrate precoated with indium tin oxide (ITO), modified by spin-coating a polyethylenedioxythiophene / polystyrenesulfonate (PEDOT / PSS) layer (30 nm), the cathode being Al (150 nm). ) With Ca (5 nm) capped. Initial vacuum levels were 2 to 6 ^10-6 millibars. The encapsulated device was tested in air under AM1.5G irradiation (100 mW / cm 2) using a xenon solar simulator (Oriel 300W solar simulator).

Notes on efficiency naming: Examples 1 and 2 were analyzed without calibration of the solar simulator (Oriel) to normalize efficiency, with high MW P3HT characterized by '100' efficiency and low MW P3HT '120' Characterized in, the efficiency was improved by 20%. Example 3 was analyzed with a calibrated solar simulator (100 mW / cm 2) and the efficiency figures of this cell were absolute.

Example 1 Low MW P3HT: PCBM Active Layer (MW = 5k) (Unoptimized) Data is provided in FIG. 3. Note that the efficiency of this material is 20% greater compared to the higher MW analogs. Note: An uncalibrated solar simulator (AM 1.5) was used as the light source and normalized efficiency was used for comparison purposes.

Example 2 (Comparative): High MW P3HT: PCBM active layer (MW = 15k) (non-optimized) data is provided in FIG. 4. The reduced curve factor and current reduced the efficiency compared to the low MW case. Note: An uncalibrated solar simulator (AM 1.5) was used as the light source and normalized efficiency was used for comparison purposes.

Example 3: Low MW P3HT was taken and optimized for increased efficiency. 2.5% efficiency was reported by a calibrated solar simulator with AM 1.5 solar spectrum. Data is provided in FIG. 5.

Claims (80)

A composition comprising at least one regioregular polythiophene and at least one n-type semiconductor having a number average molecular weight of about 9,000 or less as determined by gel permeation chromatography in chloroform. The composition of claim 1 wherein the number average molecular weight is about 1,000 to about 9,000 and the polydispersity of the polythiophene is about 1.1 to about 1.5. The composition of claim 1 wherein the number average molecular weight is about 2,500 to about 9,000. The composition of claim 1 wherein the number average molecular weight is about 6,000 to about 9,000. 5. The composition of claim 1, wherein the regioregular polythiophene is a homopolymer or copolymer. 6. 5. The composition of claim 1, wherein the regioregular polythiophene is a homopolymer. 7. The composition of claim 1, wherein the regioregular polythiophene is a 3-substituted polythiophene. 8. The composition of claim 1, wherein the regioregular polythiophene is a 3-alkyl substituted polythiophene. 9. The composition of claim 1, wherein the regioregular polythiophene is a polythiophene soluble in an organic solvent. The composition of claim 1, wherein the regioregular polythiophene is a polythiophene soluble in a halogenated aromatic solvent. The composition of claim 1, wherein the n-type semiconductor comprises nanoparticulate semiconductors. The composition of claim 1, wherein the n-type semiconductor comprises a fullerene derivative. The composition of claim 1 wherein the weight ratio of regioregular polythiophene to n-type semiconductor is from about 4: 1 to about 0.5: 1. The composition of claim 1, wherein the weight ratio of regioregular polythiophene to n-type semiconductor is about 3: 1 to about 0.5: 1. The composition of claim 1, wherein the weight ratio of regioregular polythiophene to n-type semiconductor is from about 2.5: 1 to about 1: 1. The composition of claim 1, which is in the form of a film of about 500 nm or less. 17. The composition of any one of the preceding claims in the form of a film of about 250 nm or less. The composition of claim 1, wherein the weight average molecular weight is about 6,000 to 9,000, the regioregular polythiophene is a homopolymer, and the n-type semiconductor is a fullerene derivative. The method of claim 1, wherein the regioregular polythiophene is a homopolymer and a trisubstituted polythiophene, the n-type semiconductor is a fullerene derivative and their weight ratio is from about 2.5: 1 to 19. 1: 1 composition. 20. The regioregular polythiophene of claim 1, wherein the regioregular polythiophene is a 3-alkyl substituted polythiophene having a molecular weight of about 2,500 to about 9,0000, and a polydispersity of about 1.1 to about 1.5. Wherein the n-type semiconductor is a fullerene derivative. A photovoltaic device comprising at least one active layer comprising at least one regioregular polythiophene and at least one n-type semiconductor, and a plurality of electrodes, having a number average molecular weight of about 9,000 or less as determined by gel permeation chromatography in chloroform. The device of claim 21, further comprising a hole injection layer. 23. An apparatus according to claim 21 or 22 which provides for a characteristic of an efficiency (E) of at least 2.5%. 24. The device of any of claims 21-23, wherein the device provides a characteristic of efficiency of at least 3%. 25. The device of any of claims 21-24, which provides a property of at least 4% efficiency. 26. The device of any of claims 21-25, wherein the active layer film thickness is about 500 nm or less. 27. The device of any of claims 21-26, wherein the active layer film thickness is about 250 nm or less. 28. The device of any of claims 21-27, wherein the number average molecular weight is about 1,000 to about 9,000 and the polydispersity of the polythiophene is about 1.1 to about 1.5. 29. The device of any of claims 21-28, wherein the number average molecular weight is from about 2,500 to about 9,000. 30. The device of any of claims 21-29, wherein the number average molecular weight is from about 7,000 to about 9,000. 31. The device of any of claims 21-30, wherein the regioregular polythiophene is a homopolymer or copolymer. 32. The device of any of claims 21-31, wherein the regioregular polythiophene is a homopolymer. 33. The device of any of claims 21-32, wherein the regioregular polythiophene is a 3-substituted polythiophene. 34. The device of any of claims 21-33, wherein the regioregular polythiophene is a 3-alkyl substituted polythiophene. 35. The device of any of claims 21-34, wherein the regioregular polythiophene is a polythiophene soluble in an organic solvent. 36. The device of any of claims 21-35, wherein the regioregular polythiophene is a polythiophene soluble in a haloaromatic solvent. 37. The device of any of claims 21-36, wherein the n-type semiconductor comprises nanoparticulate semiconductor. 38. The apparatus of any of claims 21-37, wherein the n-type semiconductor comprises a fullerene derivative. The device of claim 21, wherein the weight ratio of regioregular polythiophene to n-type semiconductor is about 4: 1 to about 0.5: 1. 40. The device of any of claims 21-39, wherein the weight ratio of regioregular polythiophene to n-type semiconductor is from about 3: 1 to about 0.5: 1. 41. The method of any one of claims 21-40, comprising a hole injection layer, having a number average molecular weight of about 6,000 to about 9,000, a polydispersity of about 1.1 to about 1.5, and regioregular polythiophene alone A device wherein the n-type semiconductor is a fullerene derivative. 42. The method according to any of claims 21 to 41, wherein the regioregular polythiophene is a homopolymer and a trisubstituted polythiophene, the n-type semiconductor is a fullerene derivative and their weight ratio is from about 2.5: 1 to about 1 : 1, and the efficiency (E) is about 2.5% or more. 43. The device of any of claims 21-42, wherein the device efficiency (E) is at least 3%, the curve factor is at least 0.56, the short circuit current is at least 7.7 mA / cm 2, and the open circuit voltage is at least about 0.58 V. Device. The method of claim 21, wherein the regioregular polythiophene is a 3-alkyl substituted polythiophene having a number average molecular weight of about 6,000 to about 9,000, the n-type semiconductor is a fullerene derivative, E) 2.5% or more, curve factor is 0.4 or more, short circuit current is 6 mA / cm <2> or more, and open circuit voltage is about 0.55V or more. A composition comprising at least one regioregular polythiophene, at least one n-type semiconductor, and at least one halogenated aromatic solvent as determined by gel permeation chromatography in chloroform having a number average molecular weight of about 9,000 or less. 46. The composition of claim 45, wherein the halogenated aromatic solvent comprises a chlorinated aromatic solvent. 47. The composition of claim 45 or 46, wherein the polythiophene polydispersity is from about 1.1 to about 1.5. 48. The composition of any one of claims 45-47, wherein the solids content is from about 30 to about 70 weight percent. 49. The composition of any of claims 45-48, wherein the ratio of regioregular polythiophene to n-type semiconductor is from about 4: 1 to about 0.5: 1. The composition of any one of claims 45-49 wherein the n-type semiconductor is a fullerene derivative. A composition is prepared comprising one or more regioregular polythiophenes, one or more n-type semiconductors, and one or more halogenated aromatic solvents, measured by gel permeation chromatography in chloroform, having a number average molecular weight of about 9,000 or less, and removing the solvent. A method of making a film comprising preparing a film comprising regioregular polythiophene and an n-type semiconductor, and annealing the film. The method of claim 51, wherein the annealing is performed at a temperature about 50 ° C. or less above the glass transition temperature of the film. 53. The method of claim 51 or 52, wherein the film is formed over the hole injection layer. 54. The method of any one of claims 51-53, further comprising a photovoltaic device comprising an annealed film. 55. The method of any one of claims 51-54, wherein the polythiophene polydispersity is from about 1.1 to about 1.5. The method of any one of claims 51-55, wherein the polythiophene comprises poly (3-alkylthiophene). 57. The method of any one of claims 51-56, wherein the n-type semiconductor is a fullerene derivative. 58. The method of any one of claims 51-57, wherein the polythiophene comprises poly (3-alkylthiophene) and the n-type semiconductor is a fullerene derivative. 59. The method of any one of claims 51-58, wherein the solvent comprises a halogenated aromatic solvent. 60. The film of any of claims 51 to 59, wherein the polythiophene comprises poly (3-alkylthiophene), the n-type semiconductor is a fullerene derivative, the solvent comprises a halogenated aromatic solvent, and the annealing film The process is carried out at a temperature of about 50 ℃ or less than the glass transition temperature of. A composition comprising at least one regioregular polythiophene and at least one n-type semiconductor having a number average molecular weight of about 9,000 or less and a polydispersity of about 1.1 to about 1.5, as determined by gel permeation chromatography in chloroform. 62. The composition of claim 61, wherein the number average molecular weight is about 1,000 to about 9,000 and the polydispersity of the polythiophene is about 1.1 to about 1.4. 62. The composition of claim 61, wherein the number average molecular weight is about 2,500 to about 9,000. 62. The composition of claim 61, wherein the number average molecular weight is about 6,000 to about 9,000. 65. The composition of any one of claims 61-64, wherein the regioregular polythiophene is a homopolymer or copolymer. 66. The composition of any of claims 61-65, wherein the regioregular polythiophene is a homopolymer. 67. The composition of any of claims 61-66, wherein the regioregular polythiophene is a 3-substituted polythiophene. The composition of any one of claims 61-67 wherein the regioregular polythiophene is a 3-alkyl substituted polythiophene. 69. The composition of any of claims 61-68, wherein the regioregular polythiophene is a polythiophene soluble in an organic solvent. 70. The composition of any one of claims 61-69 wherein the regioregular polythiophene is a polythiophene soluble in a haloaromatic solvent. 71. The composition of any of claims 61-70, wherein the n-type semiconductor comprises nanoparticulate semiconductor. 72. The composition of any of claims 61-71, wherein the n-type semiconductor comprises a fullerene derivative. 73. The composition of any of claims 61-72, wherein the weight ratio of regioregular polythiophene to n-type semiconductor is about 4: 1 to about 0.5: 1. 74. The composition of any of claims 61-73, wherein the weight ratio of regioregular polythiophene to n-type semiconductor is about 3: 1 to about 0.5: 1. 75. The composition of any one of claims 61-74, wherein the weight ratio of regioregular polythiophene to n-type semiconductor is about 2.5: 1 to about 1: 1. 76. The composition of any one of claims 61-75, which is in the form of a film of about 500 nm or less. The composition of any one of claims 61-76 in the form of a film of about 250 nm or less. 78. The composition of any one of claims 61-77, wherein the weight average molecular weight is about 6,000 to about 9,000, the regioregular polythiophene is a homopolymer, and the n-type semiconductor is a fullerene derivative. 79. The method of any of claims 61-78, wherein the regioregular polythiophene is a homopolymer and a tri-substituted polythiophene, the n-type semiconductor is a fullerene derivative, and their weight ratio is from about 2.5: 1 to A composition that is about 1: 1. 80. The composition of any of claims 61-79, wherein the regioregular polythiophene is a 3-alkyl substituted polythiophene having a molecular weight of about 2,500 to about 9,000, and the n-type semiconductor is a fullerene derivative.

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