A 1,2,5,6-NAPHTHALENEDIIMIDE CO-POLYMER

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a PCT International application which claims the benefit of and priority to U.S. Provisional Application Ser. No. 62/538,405 filed July 28, 2017 and U.S. Patent Application Ser. No. 16/038,316 filed July 18, 2018, entitled "A 1,2,5,6-Naphthalenediimide Co- Polymer", both of which are hereby incorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR

DEVELOPMENT

[0002] None.

FIELD OF THE INVENTION

[0003] This invention relates to high performance wide-bandgap polymers for organic photovoltaics.

BACKGROUND OF THE INVENTION

[0004] Solar energy using photovoltaics requires active semiconducting materials to convert light into electricity. Currently, solar cells based on silicon are the dominating technology due to their high-power conversion efficiency. Recently, solar cells based on organic materials showed interesting features, especially on the potential of low cost in materials and processing.

[0005] Organic photovoltaic cells have many potential advantages when compared to traditional silicon-based devices. Organic photovoltaic cells are light weight, economical in the materials used, and can be deposited on low cost substrates, such as flexible plastic foils. However, organic photovoltaic devices typically have relatively low power conversion efficiency (the ratio of incident photons to energy generated). This is, in part, thought to be due to the morphology of the active layer. The charge carriers generated must migrate to their respective electrodes before recombination or quenching occurs. The diffusion length of an exciton is typically much less than the optical absorption length, requiring a tradeoff between using a thick, and therefore resistive, cell with multiple or highly folded interfaces, or a thin cell with a low optical absorption efficiency. [0006] Angular-shaped 1,2,5,6-naphthalene tetracarboxylic diimide (NDI) monomers have demonstrated high conductivity in other organic electronic applications. There exists a need NDI based polymers with low polymer bandgaps.

BRIEF SUMMARY OF THE DISCLOSURE

rising a repeat unit A, wherein repeat unit A comprises

and at least one repeat unit B, wherein repeat unit B comprises an aryl

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] A more complete understanding of the present invention and benefits thereof may be acquired by referring to the follow description taken in conjunction with the accompanying drawings in which:

[0010] Figure 1 depicts a conventional device architecture and an inverted device architecture.

[0011] Figure 2 depicts the ¾ NMR spectrum of

[0012] Figure 3 depicts the ¾ NMR spectrum of [0013] Figure 4 depicts the ¾ NMR spectrum of

[0014] Figure 5 depicts the ¾ NMR spectrum of

[0015] Figure 6 depicts the ¾ NMR spectrum of

[0016] Figure 7 depicts the ¾ NMR spectrum of

[0017] Figure 8 depicts the ¾ NMR spectrum of [0018] Figure 9 depicts the UV- Visible absorption spectra of the polymer A and polymer C.

[0019] Figure 10 depicts the UV- Visible absorption spectra of the polymer A and polymer C as a result of the solar simulator.

DETAILED DESCRIPTION

[0020] Turning now to the detailed description of the preferred arrangement or arrangements of the present invention, it should be understood that the inventive features and concepts may be manifested in other arrangements and that the scope of the invention is not limited to the embodiments described or illustrated. The scope of the invention is intended only to be limited by the scope of the claims that follow.

[0021] "Alkyl," as used herein, refers to an aliphatic hydrocarbon chains. In one embodiment, the aliphatic hydrocarbon chains are of 1 to about 100 carbon atoms, preferably 1 to 30 carbon atoms, more preferably, 1 to 20 carbon atoms, and even more preferably, and includes straight and branched chains such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n- pentyl, isopentyl, neo-pentyl, n-hexyl, and isohexyl. In this application alkyl groups can include the possibility of substituted and unsubstituted alkyl groups.

[0022] "Alkoxy," as used herein, refers to the group R— O— where R is an alkyl group of 1 to 100 carbon atoms. In this application alkoxy groups can include the possibility of substituted and unsubstituted alkoxy groups.

[0023] "Aryl" as used herein, refers to an optionally substituted, mono-, di-, tri-, or other multicyclic aromatic ring system having from about 5 to about 50 carbon atoms (and all combinations and subcombinations of ranges and specific numbers of carbon atoms therein), with from about 6 to about 20 carbons being preferred. Non-limiting examples include, for example, phenyl, naphthyl, anthracenyl, and phenanthrenyl. Aryl groups can be optionally substituted with one or with one or more Rx. In this application aryl groups can include the possibility of substituted aryl groups, bridged aryl groups and fused aryl groups.

[0024] "Ester", as used herein, represents a group of formula— COOR wherein R represents an "alkyl", "aryl", a "heterocycloalkyl" or "heteroaryl" moiety, or the same substituted as defined above [0025] "Ketone" as used herein, represents an organic compound having a carbonyl group linked to a carbon atom such as— C(0)Rx wherein Rx can be alkyl, aryl, cycloalkyl, cycloalkenyl or heterocycle.

[0026] "Amide" as used herein, represents a group of formula "— C(0) R ^x R ^y ," wherein R ^x and R ^y can be the same or independently H, alkyl, aryl, cycloalkyl, cycloalkenyl or heterocycle.

[0027] The following examples of certain embodiments of the invention are given. Each example is provided by way of explanation of the invention, one of many embodiments of the invention, and the following examples should not be read to limit, or define, the scope of the invention.

[0028] Device architecture

[0029] When used as a photovoltaic device the architecture may be a conventional architecture device, while in others it may be an inverted architecture device. A conventional architecture device typically comprised of multilayered structure with a transparent anode as a substrate to collect positive charge (holes) and a cathode to collect negative charge (electrons), and a photoactive layer sandwiched in between two electrodes. An additional charge transport interlayer is inserted in between active layer and electrode for facile hole and electron transport. Each charge transport layer can be consisted of one or more layers. An inverted device has the same multilayered structure as the conventional architecture device whereas it uses a transparent cathode as a substrate to collect electrons and a cathode to collect holes. The inverted device also has the photo-active layer and additional charge transport layers sandwiched in between two electrodes. Figure 1 depicts a conventional device architecture and an inverted device architecture. Repeat Unit A:

repeat unit A comprises a 1,2,5, 6-naphthalenediimide monomer

[0031] In one embodiment, the method of synthesizing the 1,2,5, 6-Naphthalenediimide monomer can involve converting 2,6-naphthalene diol to produce

. In one embodiment of the method, the temperature does not exceed about 290°C. In other embodiments, none of the reactions in this method exceed 280°C, 270°C, 260°C, 250°C, 240°C, 230°C, 220°C, 210°C, 200°C, 190°C, 180°C, 170°C, 160°C, or even

150°C. In yet another embodiment, the conversion from 2,6-naphthalene diol to produce

not contain cyanide-containing reagents.

[0032] In one embodiment, the method of producing 1,2,5,6-naphthalenediimide monomer

can begin by brominating 2,6-naphthalene diol to produce: The diols of

are then converted into . During this conversion, the triflic anhydride can either be added before the pyridine or after the pyridine. upling condition to form was then oxidized to produce:

as then followed b to A conversion of produce

by a bromination to produce

completes the method.

[0033] In one embodiment, the method of producing a 1,2,5,6-naphthalenediimide monomer can also be expressed as a series of reactions. In this method reacting 2,6-naphthalene diol to

produce reaction mixture A, wherein reaction mixture A compri

is then reacted to produce reaction mixture B, wherein reaction mixture B

comprises: then reacted to produce reaction mixture C, wherein reaction mixture C compri

is then reacted to produce reaction mixture D, wherein reaction mixture D comprises:

produce reaction mixtu re E, wherein reaction mixture E comprises:

then reacted to produce reaction mixture F, wherein reaction mixture F comprises: The final reaction involves reacting

to produce reaction mixture G, wherein reaction mixture G

comprises:

[0034] In a more detailed embodiment of producing al,2,5,6-naphthalenediimide monomer, the method can begin by taking a solution of 2,6-naphthalene diol (10.16 g, 63.43 mmol) in tetrahydrofuran (110 mL) and cooling the solution to about 0 °C, then treated slowly with N- bromosuccinimide (22.58 g, 0.13 mol). The flask was then topped with a water condenser and heated to around 60°C for around 3 hours, then cooled to room temperature. This reaction mixture A was diluted with a saturated aqueous Na ₂ S ₂ 03 solution (-250 mL) and water (-1.5 L), and the resulting solid was collected by filtration, and then left under vacuum for around 18 hours. The desired product, mol, 97% yield), was obtained as a tan

solid. The ¾ M R spectrum of is shown in Figure 2.

[0035] The next reaction in the method involves ch in a Schlenk flask. A hot, oven-dried Schlenk flask was evacuated for about 30 min, refilled with argon, then

charged with (io g, 31.45 mmol) and evacuated for about 1 hour. The flask was refilled with argon and dry dichloromethane (300 mL) was added. The resulting suspension was cooled to about 0 °C for about 15 min, then triflic anhydride (11.62 mL, 0.069 mol) was added dropwise, followed by the dropwise addition of pyridine (15.2 mL, 0.189 mol). The reaction was then gradually warmed to room temperature and stirred for about 18 hours. The reaction mixture was diluted with dichloromethane and water, then transferred to a separatory funnel. The aqueous layer was acidified with hydrochloric acid, then extracted with dichloromethane. The combined organic extracts were dried (MgSCn), filtered, and concentrated into reaction mixture B. Reaction mixture B was then diluted with a mixture of dichloromethane and acetone, applied to the top of a 4" x 6" column, and eluted with dichloromethane. All fractions

containing concentrated. The material was then dissolved in dichloromethane, adsorbed onto silica gel and purified on a 340 g Biotage silica gel cartridge with -30% dichloromethane/hexanes gradient. Fractions containing pure product

concentrated (15.2 g, 0.026 mol, 83% yield) and was a white,

crystalline solid. The ¾ MR spectrum of is shown in Figure 3.

[0036] The next reaction in the method involves first taking a hot, oven-dried Schlenk flask

and evacuating for aboutl hour, followed by refilled with argon. (11.6 g, 19.9 mmol), Cul (1.14 g, 6 mmol), and Pd(PPh ₃ ) ₂ Cl2 (2.1 g, 3 mmol) are then added to the flask, and then degassed for about 30 min. After refilling with argon, dry tetrahydrofuran (50 mL, mol) was added, and two freeze-pump-thaw cycles were performed. The mixture was then warmed to room temperature and treated with triethylamine (16.7 mL, 120 mmol) and trimethylsilylacetylene (28.4mL, 200 mmol). The reaction was then stirred at about 40 °C for about 3 days. The reaction mixture C was cooled to room temperature, then poured into water and extracted with dichloromethane. The combined organic extracts were dried (MgS04), filtered, and concentrated. The crude material was dissolved in dichloromethane, adsorbed onto silica gel and purified on a 340 g Biotage column with a 0—15% dichloromethane/hexanes gradient. Any fractions containing product were concentrated to produce 16 mmol, 62% yield)

as an orange solid. The ¾ MR spect rum of is shown in Figure 4.

[0037] In a flask, (3.78 g, 7.4 mmol), FeCl3(H ₂ 0) ₆ (0.4 g, 1.5 mmol), water (30 mL), and tert-butylhydroperoxide solution (70 wt% in water, 24.5 mL) were combined. The mixture was stirred at room temperature for 1 h, then treated with NaOH (4.7g, 117.9 mmol), topped with a water condenser and Ar inlet, and heated to about 80 °C for about 18 hours. The reaction mixture was then cooled to room temperature, diluted with water, cooled to 0 °C, and acidified with HC1 to produce reaction mixture D. The reaction mixture D was filtered through filter paper, the solid was discarded, and the filtrate was transferred to a separatory funnel and extracted with ethyl acetate. The combined organic extracts were dried (MgS0 ₄ ), filtered, and

concentrated, then left under vacuum overnig was obtained as a brown-orange solid (1.89 g, 6 mmol, 84% yield). The material was carried forward without any

purification. The ¹ H MR spectrum of is shown in Figure 5.

[0038] The next reaction in the method begins by taking a round bottom flask and combining

(1.89 g, 6.2 mmol) and acetic anhydride (45 mL), then topping with a water co

mixture

mmol, 9

without any purification. The ¾ MR spectrum is shown in Figure 6. [0039] The next step in the method begins by having (2.8 g, 10 mmol) in a flask and leaving it under vacuum for about 2 hours. The flask was refilled with argon, and toluene (100 mL) and 2-ethylhexylamine (5.1 mL, 31 mmol) were added. The flask was equipped with a water condenser and argon balloon, and the reaction was heated to about 110 °C for aboutl 8 hours. The reaction mixture was concentrated and the residue was treated with thionyl chloride (60 mL), topped with a water condenser and argon balloon, and heated to about 80 °C for about 5 hours. The thionyl chloride was removed via rotovap, and the remaining residue, reaction mixture F, was dissolved in dichloromethane, adsorbed onto silica gel, and purified on a 100 g Biotage silica gel column with a 30-100% dichloromethane/hexanes gradient. Reaction mixture

F was concentrated to produce mmol, 33% yield) as

a tan solid. The ¾ MR spect shown in Figure 7.

[0040] The final step in the method begins by dissolving

(1.2 g, 2 mmol) in a round bottom flask, with trifluoroacetic acid (12 mL) and sulfuric acid (3 mL), then treated portionwise with N-bromosuccinimide (1.3 g, 7 mmol). The flask was topped with an argon balloon and the reaction was heated to about 55 °C for about 18 hours. Thin layer chromatography of the reaction mixture showed some unreacted starting material, so additional N- bromosuccinimide (0.44 g, 2 mmol) was added, and the reaction stirred at about 55 C for about 1 hour. After cooling to room temperature, the reaction was quenched with ice, then transferred to a separatory funnel and extracted with dichloromethane to produce reaction mixture G. The organic extracts of reaction mixture G were then dried (MgS0 ₄ ), filtered, and concentrated. The crude material was then dissolved in dichloromethane, adsorbed onto silica, and purified on a 100 g Biotage silica gel column with a 0-100% dichloromethane/hexanes gradient. Reaction mixture

G was then concentrated to afford to produce mg, 0.586

mmol, 24% yield) as a yellow solid. The ¾ MR spectrum of

shown in Figure 8. [0041] Repeat unit B:

[0042] In one embodiment, at least one repeat unit B refers to an optionally substituted, mono- , di-, tri-, or other multicyclic aromatic ring system having from about 5 to about 50 carbon atoms (and all combinations and subcombinations of ranges and specific numbers of carbon atoms therein), with from about 6 to about 20 carbons being preferred. Non-limiting examples include, for example, phenyl, naphthyl, anthracenyl, and phenanthrenyl. Aryl groups can be optionally substituted with one or with one or more Rx. In this application aryl groups can include the possibility of substituted aryl groups, bridged aryl groups and fused aryl groups. While it is feasible that there is only one repeat unit B in the copolymer, it is also envisioned that multiple repeat unit B's can exist within the copolymer.

combinations thereof, wherein R' and R" are independently selected from the group consisting of: H, CI, F, CN, alkyl, alkoxy, alkylthio, ester, ketone and aryl groups. In another embodiment, the aryl group is a 3,3'difluror-2,2'-bithiophene, a benzo[l,2-b:4,5-b']dithiophene, a

[0044] Copolymer

[0045] When combined, repeat unit A and repeat unit B produce a copolymer. The copolymer can be regio-random or regio-regular. It is envisioned that the copolymer can be used as a photovoltaic material. It is also envisioned that the copolymer can be used as an active layer in an electronic device. In one embodiment, the number of repeat units A and B can range from about 3 to about 10,000 in the copolymer.

[0047] In one embodiment, the repeat unit A and B are alternating. It is theorized that the number of repeat units in the polymer can be from 1 to 10,000, or from 1 to 1,000 or even from 1- 100.

[0048] Anode

[0049] When used in as an organic photovoltaic device the copolymer can be used in conjunction with an anode. The anode for the organic photovoltaic device can be any conventionally known anode capable of operating as an organic photovoltaic device. Examples of anodes that can be used include: indium tin oxide, aluminum, carbon, graphite, graphene, PEDOT:PSS, copper, metal nanowires, Zn99lnOx, ZmsImOx, Zn97ln ₃ O _x , Zn95Mg ₅ 0x, Zn9oMgioO _x , and ZmsMgisOx.

[0050] Cathode [0051] When used in as an organic photovoltaic device the copolymer can be used in conjunction with a cathode. The cathode for the organic photovoltaic device can be any conventionally known cathode capable of operating as an organic photovoltaic device. Examples of cathodes that can be used include: indium tin oxide, carbon, graphite, graphene, PEDOT:PSS, copper, silver, gold, metal nanowires.

[0052] Electron transport layer

[0053] When used in as an organic photovoltaic device the copolymer can be deposited onto an electron transport layer. Any commercially available electron transport layer can be used that is optimized for organic photovoltaic devices. In one embodiment, the electron transport layer can comprise (AOx)yBO(i-y). In this embodiment, (AOx) _y and BO(i- _y > are metal oxides. A and B can be different metals selected to achieve ideal electron transport layers. In one embodiment A can be aluminum, indium, zinc, tin, copper, nickel, cobalt, iron, ruthenium, rhodium, osmium, tungsten, magnesium, indium, vanadium, titanium and molybdenum.

[0054] In one embodiment B can be aluminum, indium, zinc, tin, copper, nickel, cobalt, iron, ruthenium, rhodium, osmium, tungsten, vanadium, titanium and molybdenum.

[0055] Examples of (AOx) _y BO(i- _y ) include: (SnOx)yZnO(i-y), (AlOx)yZnO(i-y), (AlOx)ylnOz(i-y),

(AlOx)ySnOz(l-y), (AlOx)yCuOz(l-y), (AlOx)yWOz(l-y), (InOx)yZnO(l-y), (InOx)ySnOz(l-y), (InOx)yNiOz(l-y), (ZnOx)yCuOz(l-y), (ZnOx)yNiOz(l-y), (ZnOx)yFeOz(l-y), (WOx)yVOz(l-y), (WOx)yTiOz(l-y), and (WOx)yMoOz(l-y).

[0056] In an alternate embodiment, various fullerene dopants can be combined with (AOx)yBO(i-y) to make an electron transport layer for the organic photovoltaic device. Examples

of fullerene dopants that can be combined include and [6,6]-phenyl- C6o-butyric-N-2-trimethylammonium ethyl ester iodide. [0057] In the embodiment of R' can be selected from either N, O,

S, C, or B. In other embodiment R" can be alkyl chains or substituted alkyl chains. Examples of substitutions for the substituted alkyl chains include halogens, N, Br, O, Si, or S. In one example \,-' x C "^Ys i^^MH ₂ R" can be selected from , , or

Other examples of fullerene dopants that can be used include: [6,6]-phenyl-C6o-butyric-N-(2- aminoethyl)acetamide, [6,6]-phenyl-C6o-butyric-N-triethyleneglycol ester and [6,6]-phenyl-C6o- butyric-N-2-dimethylaminoethyl ester.

[0058] Organic Photovoltaic Device Fabrication

[0059] Zinc/tin oxide (ZTO):phenyl-C60-butyric-N-(2-hydroxyethyl)acetamide (PCBNOH) sol-gel solution was prepared by dissolving zinc acetate dihydrate or tin(II) acetate in 2- methoxyethanol and ethanolamine. Specifically, the ZTO:PCBNOH sol-gel electron transport layer solution was prepared by mixing 3.98 g of Zn(OAc) ₂ , 398 mg of Sn(OAc) ₂ and 20.0 mg PCBNOH in 54 mL of 2-methoxyethanol with adding 996 μΙ_, of ethanolamine. Solutions were then further diluted to 65% by adding more 2-methoxyethanol and stirred for at least an hour before spin casting onto indium tin oxide substrate to form the electron transport layer.

[0060] The polymer and the acceptor, PC70BM, in a ratio of 1 : 1.2 were dissolved in chlorobenzene at the concentration of 26 mg/mL to obtain the photoactive layer solution. The solution was stirred and heated at 80 °C overnight in a nitrogen filled glove box. The next day 3.0 vol% of 1,8-diiodooctane (DIO) was added before spin-coating of the photoactive layer.

[0061] Indium tin oxide patterned glass substrates were cleaned by successive ultra- sonications in acetone and isopropanol. Each 15-min step was repeated twice and the freshly cleaned substrates were left to dry overnight at 60 °C. Preceding fabrication, the substrates were further cleaned for 1.5 min in a UV-ozone chamber and the electron transport layer was immediately spin coated on top. [0062] Sol-gel electron transport layer solution was filtered directly onto the indium tin oxide with a 0.25 μπι poly(vinylidene fluoride) filter and spin cast at 4000 rpm for 40 s. Films were then annealed at 250 °C for 15 min, and directly transferred into a nitrogen filled glove box.

[0063] The photoactive layer was deposited on the electron transport layer via spin coating at 600 rpm for 40 s with the solution and the substrate being preheated at 110 °C and directly transferred into a glass petri dish for overnight solvent annealing.

[0064] After annealing, the substrates were loaded into the vacuum evaporator where MoCb (hole transport layer) and Ag (anode) were sequentially deposited by thermal evaporation. Deposition occurred at a pressure of < 4 x 10 ^"6 torr. MoCb and Ag had thicknesses of 5.0 nm and 120 nm, respectively. Samples were then encapsulated with glass using an epoxy binder and treated with UV light for 3 min.

[0065] Synthesis of Polymers

[0066] Three different repeat unit B's were used to produce three different polymers.

[0067] The polymers were prepared from a traditional Stille coupling reaction. The stannylated versions of the samples A, B, and C were copolymerized with

produce polymers A, B and C.

(85.9 mg, 0.095 mmol), and Pd(PPh ₃ (11 mg, 0.009 mmol) were combined, then degassed for 30 minutes. After refilling with argon, toluene (3.8 mL) and DMF (0.95 mL) were added, and the reaction mixture was degassed via three freeze-pump- thaw cycles, using liquid nitrogen to freeze the solution. The solution was then heated to 120 °C and stirred for two days under argon atmosphere. The reaction mixture was cooled to room temperature, poured into methanol (50 mL), and the polymer was collected by filtration. The polymer was purified by Soxhlet extraction, washing sequentially with acetone, hexanes, and

chloroform. The polymer, , was recovered in the chloroform fraction (76 mg, 73% yield).

(98.9 mg, 0.093 mmol), and Pd(PPh ₃ (11 mg,

0.009 mmol) were combined, then degassed for 30 minutes. After refilling with argon, toluene (3.6 mL) and DMF (0.9 mL) were added, and the reaction mixture was degassed via three freeze- pump-thaw cycles, using liquid nitrogen to freeze the solution. The solution was then heated to 120 °C and stirred for two days under argon atmosphere. The reaction mixture was cooled to room temperature, poured into methanol (50 mL), and the polymer was collected by filtration. The polymer was purified by Soxhlet extraction, washing sequentially with acetone, hexanes, chloroform, and chlorobenzene. Some of the polymer,

, was collected from the chloroform fraction mg, 22% yield), but most of the polymer was not extracted (50 mg, 43% yield). [0070] Polymer C: In a Schlenk flask, (63.9 mg, 0.099 mmol),

(120 mg, 0.099 mmol), and Pd ₂ (dba) ₃ (2.3 mg,

0.003 mmol) were combined, then degassed for 30 minutes. After refilling with argon, chlorobenzene (1.65 mL) was added, and the reaction mixture was degassed via three freeze- pump-thaw cycles, using liquid nitrogen to freeze the solution. The solution was then heated to 120 °C and stirred for two days under argon atmosphere. The reaction mixture was cooled to room temperature, poured into methanol (50 mL), and the polymer was collected by filtration. The polymer was purified by Soxhlet extraction, washing sequentially with acetone, hexanes, chloroform, and chlorobenzene. The polymer,

was recovered in the chloroform fraction

(101 mg, 73% yield).

[0071] UV- Visible Absorption Spectroscopy

[0072] Absorption spectroscopy was performed and measured in the wavelength region from 300 to 1000 nm. A blank glass slide background was subtracted from all spectra. The polymer thin film samples were prepared by spin casting a 10 mg/mL solution of polymer (in 50:50 chlorobenzene:dichlorobenzene) onto a glass slide at 1200 rpm. Figure 9 depicts the UV- Visible absorption spectra of the polymers.

[0073] UV- Visible Absorption Spectroscopy Solar Simulator

[0074] Devices with an active area of 0.08306 cm ² determined from aperture mask were tested under AM 1.5 G 100 mW/cm ² conditions with a Newport Thermal Oriel 91192 1000 W solar simulator (4" x 4" illumination size). Figure 10 depicts the UV- Visible absorption spectra of the polymers as a result of the solar simulator.

[0075] Representative current density

[0076] Representative current density - voltage characteristics are shown below in Table 1.

Table 1

[0077] Jsc (mA/cm ² ) Short-circuit current density (Jsc) is the current density that flows out of the solar cell at zero bias. Voc (V) Open-circuit voltage (Voc) is the voltage for which the current in the external circuit is zero. FF (%) fill factor (FF) is the ratio of the maximum power point divided by the open circuit voltage and the short circuit current. PCE (%) of the power conversion efficiency (PCE) of a photovoltaic cell is the percentage of the solar energy shining on a photovoltaic device that is converted into usable electricity. Rs (Ω cm ² ) series resistance (Rs) through the photovoltaic cell. Rsh (Ω cm ² ) parallel resistance though the photovoltaic cell.

[0078] In closing, it should be noted that the discussion of any reference is not an admission that it is prior art to the present invention, especially any reference that may have a publication date after the priority date of this application. At the same time, each and every claim below is hereby incorporated into this detailed description or specification as an additional embodiment of the present invention.

[0079] Although the systems and processes described herein have been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the spirit and scope of the invention as defined by the following claims. Those skilled in the art may be able to study the preferred embodiments and identify other ways to practice the invention that are not exactly as described herein. It is the intent of the inventors that variations and equivalents of the invention are within the scope of the claims while the description, abstract and drawings are not to be used to limit the scope of the invention. The invention is specifically intended to be as broad as the claims below and their equivalents.