Polymers based on 4-alkylthiothiophene / 4-alkylselenothiophene, preparation methods and applications

Abstract

The present invention discloses a polymer based on 4-alkylthiothiophene / 4-alkylselenothiophene, a preparation method and an application thereof, wherein the polymer includes a 4-alkylthiothiophene ring and / or a 4-alkylselenothiophene ring connected to the main chain of a donor-acceptor polymer as a conjugated side chain; the 4-alkylthiothiophene ring and / or the 4-alkylselenothiophene ring are connected to the donor unit of the polymer main chain. The present invention introduces 4-alkylthiothiophene (AST) or 4-alkylselenothiophene (ASeT) containing sulfur or selenium atoms to modify the side chain of the BDT unit, thereby preparing a non-fullerene polymer solar cell with stronger performance. In addition, the present invention uses a non-halogen solvent with lower toxicity than a halogen solvent to process AST or ASeT polymer materials, providing a new approach to prepare an efficient, low-cost, environmentally friendly non-fullerene polymer solar cell.

Description

Technical Field

[0001] The present invention relates to the field of organic semiconductor materials, and in particular to a polymer based on 4-alkylthiothiophene / 4-alkylselenothiophene, a preparation method and an application thereof. Background Art

[0002] Bulk heterojunction polymer solar cells have been widely concerned because of their potential for new applications, such as flexibility, lightness, environmental protection and low-cost power generation. Generally speaking, a polymer is used as an electron donor and a fullerene derivative is used as an electron acceptor material to prepare a classic bulk heterojunction polymer solar cell, and its energy conversion efficiency has reached 11%. However, due to its weak absorption in the visible light region, difficulty in energy level regulation and high cost, fullerene derivatives are no longer ideal acceptor materials in polymer solar cells. Therefore, non-fullerene (NF) acceptors, due to their strong absorption in the visible or near-infrared, easy to adjust energy levels and compatible morphology, can further improve the energy conversion efficiency of polymer solar cells. With the development of efficient ITIC and its derivatives, the efficiency of polymer solar cells has been improved to 13-14%, opening up a bright future for future commercial applications.

[0003] Similar to acceptor materials, polymer electron donors are equally important in polymer solar cells. Efficient non-fullerene polymer solar cells first require that the polymer donor and non-fullerene acceptor have matching absorption spectra, energy levels and more appropriate phase separation in the nanostructure to ensure that photon capture, charge separation and transport are as effective as possible. Therefore, developing a new polymer donor to meet the current limited number of effective non-fullerene acceptor materials is an effective way to further improve the efficiency of polymer solar cells. New basic units, different donor-acceptor polymer structures and side chain modifications have been selected as effective methods to effectively improve the performance of polymer donor materials. Among these new methods, side chain modification is a relatively easy way.

[0004] In the prior art, 4-alkoxythiophene (AOT) is coupled with benzo[1,2-b:4,5-b']dithiophene-4,8-dione as an electron-pulling side chain, which shows a lower HOMO energy level, thus increasing the open circuit voltage (V oc ) and efficiency. However, AOT-based polymers are not well matched with the current classic NF donors, resulting in low performance of polymer solar cells. In addition, AOT polymers have been plagued by high synthesis costs and low yields due to their complex synthesis routes.

[0005] In summary, it is urgent to develop a new technical solution to solve the problems existing in the existing technology and meet the needs of practical applications. Summary of the invention

[0006] Based on this, the present invention provides a feasible and effective molecular synthesis method to obtain a more efficient polymer solar cell. In the present invention, 4-alkylthiothiophene (AST) or 4-alkylselenothiophene (ASeT) containing sulfur or selenium atoms is introduced to modify the side chain of the BDT unit, thereby preparing a non-fullerene polymer solar cell with stronger performance. In addition, the present invention uses a non-halogen solvent with lower toxicity than a halogen solvent to treat the AST or ASeT polymer material, providing a new way to prepare a high-efficiency, low-cost, and environmentally friendly non-fullerene polymer solar cell.

[0007] An object of the present invention is to provide a donor-acceptor polymer comprising a 4-alkylthiothiophene ring and / or a 4-alkylselenothiophene ring connected to the main chain of the donor-acceptor polymer as a conjugated side chain;

[0008] The structural formula of the 4-alkylthiothiophene ring is

[0009]

[0010] The structural formula of the 4-alkylselenylthiophene ring is

[0011]

[0012] Wherein, R1 is selected from hydrogen atom, -(CH2) m H、-O(CH2) m H and -S(CH2) m One or more of H, m is selected from an integer in the range of 1 to 20; R2 is -(CH2) n H, n is selected from integers in the range of 1-12.

[0013] Furthermore, R1 can be a hydrogen atom, -CH3, -C2H5, -C4H9, -C6H 13 、-C8H 17 , -C 12 H 25 , 2-ethylhexyl, 2-butyloctyl, 2-hexyldecyl or 2-octyldodecyl; preferably, R1 is 2-ethylhexyl.

[0014] Furthermore, the 4-alkylthiothiophene ring and / or the 4-alkylselenothiophene ring is connected to the donor unit of the polymer main chain.

[0015] Furthermore, the molar ratio of the 4-alkylthiothiophene ring and / or the 4-alkylselenothiophene ring to the donor unit of the polymer main chain is (1-2):1.

[0016] Preferably, the molar ratio of the 4-alkylthiothiophene ring and / or the 4-alkylselenothiophene ring to the donor unit of the polymer main chain is 2:1.

[0017] Preferably, the main chain of the conjugated polymer is a donor-acceptor structure, and the molar ratio of the donor unit to the acceptor unit (D / A ratio) is 1:1, as shown below

[0018]

[0019] Furthermore, the donor unit is selected from one or more of benzo[3,4-b]dithiophene, thiophene, benzene and derivatives thereof.

[0020] Furthermore, the donor unit includes but is not limited to one of the following structures:

[0021]

[0022] Wherein, R1 is a 4-alkylthiothiophene ring or a 4-alkylselenothiophene ring. In particular, the donor unit is benzo[3,4-b]bithiophene or a derivative thereof.

[0023] Furthermore, in the donor-acceptor polymer, the acceptor unit on the main chain is selected from benzo[c][1,2,5]thiadiazole, benzo[c][1,2,5]oxadiazole, isoindoline-1,3-dione, quinoxaline, benzo[d][1,2,3]triazole, thieno[3,4-c][1,2,5]thiadiazole, thieno[3,4-b]pyrazine, thieno[3,4-b]thiophene, benzo[1,2-c:4,5 The group consisting of: [1,2,5]bis(1,2,5]thiadiazole), [1,2,5]thiadiazo[3,4-g]quinoxaline, pyrazino[2,3-g]quinoxaline, [3,3'-diindolylene]-2,2'-dione, diketopyrrolopyrrole, thienopyrroledione, thienoisoindole and derivatives having unsubstituted or alkyl-substituted thiophene or unsubstituted or alkyl-substituted thieno[2,3-b]thiophene as their bridging groups.

[0024] Furthermore, the receptor unit includes but is not limited to one of the following structures:

[0025]

[0026] In particular, the acceptor on the conjugated polymer backbone includes, but is not limited to, benzo[c][1,2,5]thiadiazole, benzo[c][1,2,5]oxadiazole, isoindole-1,3-dione, quinoxaline, benzo[d][1,2,3]thiatriazole, thio[3,4-c][1,2,5]thiadiazole, thio[3,4-b]pyrazine, thio[3,4-b]thiophene, benzo[1,2-c:4,5-c']bis([1,2,5]thiadiazole), [1,2,5]thiadiazole[3,4-g]quinoxaline, The group consisting of oxaline, pyrazino[2,3-g]quinoxaline, [3,3'-diindolylene]-2,2'-dione, benzo[1,2-c:4,5-c]thiophene-4,8-dione, thiophene[3,4-c]pyrrole-4,6(5h)-dione, 2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione and derivatives having unsubstituted or alkyl-substituted thiophene or unsubstituted or alkyl-substituted thieno[2,3-b]thiophene as bridging groups on both sides thereof, as shown in the following structures,

[0027]

[0028] Wherein R is selected from hydrogen atom, -CH3, -C2H5, -C4H9, -C6H 13 、-C8H 17 , -C 12 H 25 , 2-ethylhexyl, 2-butyloctyl, 2-hexyldecyl or 2-octyldodecyl; R2 is selected from H, CH3, C2H5, C4H9, C6H 13 、C8H 17 , C 12 H 25 , 2-ethylhexyl, 2-butyloctyl, 2-hexyldecyl or 2-octyldodecyl.

[0029] Furthermore, the number of repeating units in the donor-acceptor polymer is 10-100.

[0030] Preferably, the acceptor material is selected from 1,3-(thiophene-2-yl)-5,7-(2-ethylhexyl)benzo-[1,2-c:4,5-c]bithiophene-4,8-dione (BDD-T) modified by thiophene, 2,3-diphenyl-5,8-di(thiophene-2-yl)quinoxaline (DTQx-2F-T) modified by thiophene, 5,6-difluorobenzo[1,2,3]triazole (FTAZ-T) modified by thieno[3,4-b]thiophene (TT) modified by thieno[3,4-c]pyrrole-4,6(5H)-dione (TPD-TT) and 2,5-dithienyl-1,3,4-thiadiazole (TDZ). The above monomers can make the polymer have good photovoltaic performance and are used as the acceptor unit of the embodiment of the present invention.

[0031]

[0032] Another object of the present invention is to provide a composition comprising a blend of the donor-acceptor polymer and a non-fullerene derivative.

[0033] Further, the non-fullerene derivative is selected from one of ITIC-2F and ITIC-4F;

[0034] The structural formula of ITIC-2F is

[0035]

[0036] The structural formula of ITIC-4F is

[0037]

[0038] Another object of the present invention is to provide a method for preparing the above-mentioned 4-alkylthiothiophene ring or 4-alkylselenothiophene ring, comprising the following steps:

[0039] Preparation method of 4-alkylthiothiophene ring:

[0040] 3-bromo-2-(2-ethylhexyl)thiophene is added to a solvent, cooled at low temperature, and then an n-butyl lithium solution is added under an inert gas atmosphere. After stirring, 1,2-dimethyldisulfane is added. After stirring for reaction, the reaction is quenched with water and then purified to obtain the 4-alkylthiothiophene ring;

[0041] Preparation method of 4-alkylselenylthiophene ring:

[0042] 3-Methylselenothiophene is added to a solvent, cooled at low temperature, and then an n-butyllithium solution is added under an inert gas atmosphere. After stirring, an alkyl bromide is added. After stirring for reaction, the reaction is quenched with water and then purified to obtain the 4-alkylselenothiophene ring.

[0043] Another object of the present invention is to provide a photovoltaic device comprising the above composition.

[0044] Preferably, the technical solution of the present invention uses toluene as a solvent to dissolve the polymer:receptor blend, and spin-coats it on the device and dries it.

[0045] Another object of the present invention is to provide a method for increasing the open circuit voltage of the donor-acceptor polymer by using the donor-acceptor polymer.

[0046] The photovoltaic device of the present invention comprises a semiconductive conjugated polymer blended with fullerene or non-fullerene molecules as a photoactive layer. The semiconductive polymer has AST or ASeT functional groups as side chains, which can effectively reduce the highest occupied orbital (HOMO) energy level of the polymer, thereby increasing the open circuit voltage. Importantly, the short circuit current and fill factor of the device are not significantly changed. As a result, an improvement in energy conversion efficiency is achieved.

[0047] Compared with polymers with AOT functional groups as side chains, polymers with AST or ASeT functional groups as side chains have lower HOMO energy levels due to the fact that S and Se atoms have greater electron nucleophilic energy than O atoms and a greater hyperconjugation effect with conjugated side groups. Compared with polymer devices based on AOT side chains, polymer devices based on AST or ASeT can obtain higher open circuit voltages and thus higher energy conversion efficiency.

[0048] The present invention has the following beneficial effects:

[0049] According to an embodiment of the present invention, compared with polymers based on AOT functional groups, the introduction of AST or similar functional groups thereof can more effectively reduce the HOMO energy level of conjugated polymers, and each AST on BDT can be reduced by 0.05-0.1eV, and every 2 ASTs can be reduced to 0.1-0.2eV. As a result, the open circuit voltage of the device with AST increases accordingly compared with that of the reference device. Compared with polymer devices based on AOT side chains, the short-circuit current and fill factor of the AST device are not reduced, resulting in an increase in energy conversion efficiency. In addition, AST-based polymer photovoltaic devices treated with non-halogen solvents (such as toluene, o-xylene) also show good performance. This method can be applied to many donor-acceptor type semiconductive polymers. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A schematic diagram of the structure of the photovoltaic device prepared in Application Example 1 is shown.

[0051] Figure 2 The absorption spectra of polymer materials and those blended with ITIC derivatives are shown;

[0052] in,

[0053] Figure 2 (a) is the absorption spectrum of a single polymer material;

[0054] Figure 2 (b) is the absorption spectrum of the polymer material after blending with ITIC derivatives.

[0055] Figure 3 Shown is an energy level distribution diagram of a polymer material.

[0056] Figure 4 shows the current-voltage curve (JV) diagram of photovoltaic devices based on different polymer materials;

[0057] in,

[0058] Figure 4 (a) is the current-voltage curve (JV) of PMTT56:ITIC-2F photovoltaic device;

[0059] Figure 4 (b) is the current-voltage curve (JV) of PMOT39:ITIC-2F photovoltaic device;

[0060] Figure 4 (c) Current-voltage curve (JV) of PMSeT1:ITIC-2F and PMSeT2:ITIC-4F photovoltaic devices.

[0061] Figure 5 The external quantum efficiency curve (EQE) of photovoltaic devices based on different polymer materials is shown;

[0062] in,

[0063] Figure 5 (a) is the external quantum efficiency curve of PMTT56:ITIC-2F photovoltaic device in different solvents;

[0064] Figure 5 (b) is the external quantum efficiency curve of PMOT39:ITIC-2F photovoltaic device;

[0065] Figure 5 (c) is the external quantum efficiency curve of PMSeT1:ITIC-2F and PMSeT2:ITIC-4F photovoltaic devices.

[0066] Figure 6 TEM images of hybrid films prepared based on PMTT56:ITIC-2F are shown;

[0067] in,

[0068] Figure 6 (a) Film treated with toluene and 1% DPE;

[0069] Figure 6 (b) Film treated with o-xylene and 1% DPE;

[0070] Figure 6 (c) Film treated with chlorobenzene and 1% DPE.

[0071] Figure 7AFM images of hybrid films prepared based on PMTT56:ITIC-2F are shown (size: 5 μm×5 μm);

[0072] in,

[0073] Figure 7 (a) Film treated with toluene and 1% DPE;

[0074] Figure 7 (b) Film treated with o-xylene and 1% DPE;

[0075] Figure 7 (c) Film treated with chlorobenzene and 1% DPE. DETAILED DESCRIPTION

[0076] In order to more clearly illustrate the technical solution of the present invention, the following examples are listed. Unless otherwise stated, the raw materials, reactions and post-treatment methods shown in the examples are common raw materials on the market and technical methods well known to those skilled in the art.

[0077] The words "preferred", "preferably", "more preferably", etc. in the present invention refer to embodiments of the present invention that can provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention.

[0078] It should be understood that, except in any operating examples, or where otherwise indicated, all numbers expressing, for example, the amounts of ingredients used in the specification and claims should be understood to be modified in all instances by the term "about". Therefore, unless indicated to the contrary, the numerical parameters set forth in the following specification and the appended claims are approximate values ​​that vary depending on the desired properties to be obtained by the present invention.

[0079] The structural formula of ITIC-2F in the embodiment of the present invention is

[0080]

[0081] The structural formula of ITIC-4F in the embodiment of the present invention is

[0082]

[0083] Preparation Example 1

[0084] The preparation of 2-(2-ethylhexyl)-3-methylselenothiophene (3ASeT) comprises the following steps:

[0085] 3-Methylselenothiophene (19.57 g, 110.50 mmol) and anhydrous tetrahydrofuran (120 mL) were added to a pre-dried 500 mL flask, and the solution was cooled to -78 ° C. Under argon protection, 48.4 mL of 2.4 mol / L n-butyl lithium solution was added dropwise. The mixture was stirred at this temperature for 1.0 h, and then 2-ethylhexyl bromide (42.7 g, 221 mmol) was slowly added, and then stirred at room temperature overnight, and then the reaction was quenched with water. The organic layer was extracted with ethyl acetate, washed with water 3 times, dried with anhydrous magnesium sulfate, and then the solvent was removed under reduced pressure. The target product was finally obtained by distillation (0.1 MPa, 101-110 ° C) 19.53 g, yield: 61.1%.

[0086] 1 H NMR (400MHz, CDCl3, δ): 7.17 (d, J = 5.2 Hz, 1H), 7.01 ( d, J = 5.2 Hz, 1H), 2.86 ( d, J = 7.1 Hz, 2H), 2.24 ( s,3H),1.64(dt,J=11.9,6.5Hz,1H),1.33(dq,J=9.8,5.8,4.6Hz,8H),0.92(q,J=4.0,3.5Hz,6H).

[0087] Preparation Example 2

[0088] The preparation of 2-(2-ethylhexyl)-3-methylthiothiophene (3AST) comprises the following steps:

[0089] 3-Bromo-2-(2-ethylhexyl)thiophene (5.74 g, 20.85 mmol) and anhydrous hexane (30 mL) were added to a pre-dried 250 mL flask and the solution was cooled to -78 °C. Under argon protection, n-butyl lithium solution (1.6 M inhexane, 13.03 mL) was added dropwise. Keep at this temperature for 1 h, and then slowly drip 1,2-dimethyldisulfane (1.96 g, 20.85 mmol). Stir overnight at room temperature, and then quench the reaction with water. The organic layer was extracted with dichloromethane, rinsed with water 3 times, dried with anhydrous magnesium sulfate, and then the solvent was removed under reduced pressure. The target product 4.03 g was obtained by distillation (0.1 MPa, 82-88 °C), with a yield of 79.8%.

[0090] 1H NMR (400MHz, CDCl3, δ): 7.13 (d, J = 5.3Hz, 1H), 6.97 (d, J = 5.3Hz, 1H), 2.81 (d, J = 7.1Hz, 2 H),2.36(s,3H),1.66-1.58(m,1H),1.31(dq,J=15.0,5.0,4.2Hz,8H),0.95-0.79(m,6H).

[0091] Example 1

[0092] The synthesis of PASeT2 includes the following steps:

[0093] 1. Preparation of Sn2-BDT-ASeT as part of the donor. The synthetic route is as follows:

[0094]

[0095] 3ASeT-substituted benzodithiophene (BDT-ASeT) was obtained by reacting 3ASeT with benzo[1,2-b:4,5-b']dithiophene-4,8-dione. The obtained BDT-ASeT was then subjected to lithiation with n-butyllithium (n-BuLi) and then stanned with Me3SnCl to obtain the target product.

[0096] Specifically, the steps include:

[0097] (1) Synthesis of BDT-ASeT:

[0098] 3ASeT (8.68 g, 30.0 mmol) and anhydrous tetrahydrofuran (110 mL) were added to a pre-dried 250 mL flask, the solution was cooled to 0 ° C, and 20.6 mL of 1.6 mol / L n-butyl lithium solution was added dropwise under argon protection. The mixture was kept at 0 ° C for 1.5 h and then warmed to room temperature. After that, benzo [1,2-b: 4,5-b'] dithiophene-4,8-dione (2.75 g, 12.5 mmol) was added in one portion. The reaction was carried out at 80 ° C for 1.5 h. After cooling to 0 ° C, SnCl 2·2H2O (16.86 g, 74.75 mmol) solution in 10% HCl (70 mL) was added and stirred at 80 ° C for another 2 h. After cooling to room temperature, it was extracted with ethyl acetate and washed with brine several times. Further purification by column chromatography using dichloromethane / hexane (v / v: 1 / 9) as eluent afforded 5.37 g of a yellow oil, yield: 56.2%.

[0099] 1H NMR (400MHz, CDCl3, δ): 7.65 (d, J = 5.7Hz, 2H), 7.48 (d, J = 5.7Hz, 2H), 7.37 (s, 2H), 2.94 (d, J = 7 .1Hz,4H),2.32(s,6H),1.72(dt,J=12.2,5.9Hz,2H),1.49-1.29(m,16H),1.01-0.86(m,12H).

[0100] (2) Synthesis of Sn2-BDT-ASeT:

[0101] In a 100 mL argon-purged flask, BDT-ASeT (1.04 g, 1.36 mmol) was dissolved in anhydrous tetrahydrofuran (20 mL), and then 2.04 mL of a 1.6 mol / L solution of n-butyl lithium was added at -78 °C. The reaction mixture was then stirred at this temperature for 1.5 h. Subsequently, 3.67 mL of a 1.0 mol / L solution of trimethylstannyl chloride was added, and the mixture was stirred at room temperature overnight. The organic layer was extracted with ether, washed several times with water, and concentrated to give a crude product. 1.06 g of the target product was obtained by recrystallization from isopropanol with a yield of 71.7%.

[0102] 1 H NMR (400MHz, CDCl3, δ): 7.67 (s, 2H), 7.38 (s, 2H), 3.02-2.85 (m, 4H), 2.32 (s, 6H), 1.73 (dt, J = 11. 8, 6.1Hz, 2H), 1.40 (ddd, J=32.1, 18.3, 6.3Hz, 16H), 0.94 (dt, J=20.0, 7.2Hz, 12H), 0.41 (s, 18H).

[0103] 2. Preparation of Br2-FTAZ-T as the acceptor moiety

[0104] 4,7-Di(5-bromothiophene)-5,6-2-(2-isohexadecyl)-2-hydrogen-benzo[1,2,3]triazole (Br2-FTAZ-T) was synthesized according to the previously reported method (J.Am.Chem.Soc.2011,133,4625).

[0105] 3. Preparation of donor-acceptor polymer PASeT2

[0106] The donor-acceptor polymer was prepared by Stille polycondensation of a ditinated BDT donor unit and a dibrominated acceptor unit in a toluene / DMF mixed solvent using Pd(PPh3)4 as a catalyst to obtain the polymer.

[0107] The synthetic route of PASeT2 is as follows:

[0108]

[0109] Sn2-BDT-ASeT (230.1 mg, 0.211 mmol), Br2-FTAZ-T (148.0 mg, 0.211 mmol) and Pd(PPh3)4 (10.1 mg, 0.009 mmol) were added to a 25 mL pre-dried flask, followed by 10 mL toluene and 1.0 mL DMF. The mixture was kept at 120 ° C for 24 h under argon protection. When cooled to room temperature, the crude product was filtered through diatomaceous earth and collected by precipitation from acetone. The solid was then rinsed with methanol, acetone, and hexane in a Soxhlet extractor to remove oligomers and impurities. Afterwards, the remaining solid was dissolved in chloroform and precipitated in methanol again. 259.7 mg of red solid was obtained, yield: 94.2%. Mn: 38.2 kDa; PDI: 1.99.

[0110] Example 2

[0111] The synthesis route of PASeT1 is as follows:

[0112]

[0113] Sn2-BDT-ASeT (244.8 mg, 0.2245 mmol), TPD-TT-Br2 (232.61 mg, 0.2245 mmol) and Pd(PPh3)4 (11.41 mg, 0.00988 mmol) were added to a 25 mL clean flask. Under argon protection, 10 mL of toluene was added, and after reacting at 120 ° C for 12 hours, the obtained product was collected by washing with methanol. Then, the product was further washed by Soxhlet extraction with methanol, acetone, n-hexane, and chloroform. The solution in chloroform was concentrated and then precipitated in methanol. After being pumped dry, 320.8 mg of polymer was obtained. Yield: 84.20%. Mn: 36.2 kDa; PDI: 2.07.

[0114] Example 3

[0115] The synthesis route of PMTT56 is as follows:

[0116]

[0117] Sn2-BDT-AST (174.83 mg, 0.1754 mmol), TPD-TT-Br2 (181.75 mg, 0.1754 mmol) and Pd(PPh3)4 (8.8 mg, 0.00778 mmol) were added to a 25 mL clean flask. Under argon protection, 4.5 mL of toluene was added, and after reacting at 120 ° C for 12 hours, the obtained product was collected by washing with methanol. Then, the product was further washed by Soxhlet extraction with methanol, acetone, n-hexane, and chloroform. The solution in chloroform was concentrated and then precipitated in methanol. After being pumped dry, 256.2 mg of polymer was obtained. Yield: 92.70%. Mn: 60.0 kDa; PDI: 1.98.

[0118] Application Example 1

[0119] Preparation of photovoltaic devices containing PMTT56.

[0120] A photovoltaic device with a structure of ITO / PEDOT:PSS / photoactive layer / PDINO / Ag is prepared. Indium tin oxide (ITO) is the bottom layer. The device includes a transparent metal oxide electrode, namely ITO and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) layer as an anode, a PDINO-modified Ag electrode as a cathode, and a photoactive layer made of AST or ASeT polymer and ITIC derivatives sandwiched between the two electrodes. In this embodiment, the polymer of AST is PMTT56, and the ITIC derivative selected is ITIC-2F.

[0121] The device preparation process includes the following steps: First, the ITO substrate was ultrasonically cleaned in detergent, deionized water, acetone and isopropanol in turn, then dried in an oven, and then treated with UV-ozone cleaning for 15 minutes. The aqueous solution of PEDOT:PSS was filtered through a 0.22μm filter head, then spin-coated on the ITO electrode at 2500rpm / 30s, and annealed at 150℃ in air for 10min. The thickness of the PEDOT:PSS layer was about 40nm. Subsequently, it was transferred to a glove box with a nitrogen atmosphere. PMTT56:ITIC-2F was mixed and dissolved in o-dichlorobenzene / 1,8-diiodooctane (99:1, v / v) or xylene / diphenyl ether (99:1, v / v) or toluene / diphenyl ether (99:1, v / v) in a mass ratio of 1:1, where the concentration of the polymer was 8mg / mL.

[0122] In a nitrogen glove box, the mixed solution was spin-coated on a PEDOT:PSS substrate to form a PMTT56:ITIC-2F film with a thickness of about 110 nm. PDINO was then spin-coated on the active layer and the electrode was evaporated. The resulting device was transferred to a vacuum evaporation chamber and heated to 3×10 -6 100nm of metallic silver was evaporated under a vacuum of mbar, and the area of ​​the photovoltaic device was 4.5mm 2 .

[0123] Figure 1 A schematic diagram of the structure of the photovoltaic device prepared in Application Example 1 is shown.

[0124] Application Example 2

[0125] Preparation of photovoltaic device containing PASeT1 The difference between this application example and application example 1 is that the photoactive layer uses PASeT1:ITIC-2F, and the other components and preparation methods are the same.

[0126] Application Example 3

[0127] Preparation of photovoltaic device containing PASeT2 The difference between this application example and application example 1 is that the photoactive layer uses PASeT2:ITIC-4F, and the other components and preparation methods are the same.

[0128] Comparative application example 1

[0129] Preparation of photovoltaic devices containing PMOT39.

[0130] The molecular structure of PMOT39 is as follows:

[0131]

[0132] A photovoltaic device with a structure of ITO / PEDOT:PSS / photoactive layer / PDINO / Ag is prepared. Indium tin oxide (ITO) is the bottom layer. The device includes a transparent metal oxide electrode, namely, ITO and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) layer as an anode, a PDINO-modified Ag electrode as a cathode, and a photoactive layer made of MOT polymer and ITIC derivative sandwiched between the two electrodes. In this embodiment, the polymer of MOT is PMOT39, and the ITIC derivative selected is ITIC-2F.

[0133] The device preparation process includes the following steps: First, the ITO substrate is ultrasonically cleaned in detergent, deionized water, acetone and isopropanol in turn, then dried in an oven, and then cleaned with UV-ozone for 15 minutes. The aqueous solution of PEDOT:PSS is filtered through a 0.22μm filter head, then spin-coated on the ITO electrode at 2500rpm / 30s, and annealed at 150℃ in air for 10min. The thickness of the PEDOT:PSS layer is about 40nm. Subsequently, it is transferred to a glove box with a nitrogen atmosphere. PMOT39:ITIC-2F is mixed and dissolved in o-dichlorobenzene / 1,8-diiodooctane (99:1, v / v) or xylene / diphenyl ether (99:1, v / v) or toluene / diphenyl ether (99:1, v / v) in a mass ratio of 1:1, where the concentration of the polymer is 8mg / mL.

[0134] In a nitrogen glove box, the mixed solution was spin-coated on a PEDOT:PSS substrate to form a PMOT39:ITIC-2F film with a thickness of about 110 nm. PDINO was then spin-coated on the active layer and the electrode was evaporated. The resulting device was transferred to a vacuum evaporation chamber and heated to 3×10 -6 100nm of metallic silver was evaporated under a vacuum of mbar, and the area of ​​the photovoltaic device was 4.5mm 2 .

[0135] Test Example 1

[0136] The donor-acceptor polymers were tested for performance.

[0137] Test method:

[0138] First, the absorption spectra of PMTT56, PMOT39, PASeT1 and PASeT2 were tested, and then the absorption spectra of different polymers blended with ITIC derivatives were tested.

[0139] The HOMO / LUMO energy levels of the polymers were then determined by cyclic voltammetry in acetonitrile solution using ferrocene as an external standard and n-Bu4NPF6 as a conducting electrolyte.

[0140] The test results are as follows Figure 2 , Figure 3 And as shown in Table 1.

[0141] Figure 2 The absorption spectra of polymer materials and those blended with ITIC derivatives are shown;

[0142] in,

[0143] Figure 2 (a) is the absorption spectrum of a single polymer material;

[0144] Figure 2 (b) is the absorption spectrum of the polymer material after blending with ITIC derivatives.

[0145] Figure 3 Shown is an energy level distribution diagram of a polymer material.

[0146] Table 1 shows the optical and physical properties of PMTT56, PASeT2, PASeT1 and PMOT39.

[0147] Table 1 Optical and physical properties of polymers

[0148]

[0149] according to Figure 2 It can be concluded that in the absorption spectrum, the absorption sidebands of the three polymer materials PMTT56, POT39 and PASeT1 are extremely close, indicating that the three polymers have very close optical band gaps, which indirectly indicates that the selenium atoms and sulfur atoms with larger atomic radius do not destroy the conjugation of the molecular skeleton and the π-π stacking between molecules. * The absorption is broader, which makes the polymer material containing selenium atoms have a broader absorption. In addition, it can also be seen that PASeT1 has a stronger π-π * The absorption of PMTT56, PMOT39, PASeT1 and PASeT2 indicates that the polymer material is easier to achieve photoexcitation and thus has better photoresponsivity. Based on the absorption sidebands, it can be estimated that the optical band gaps of PMTT56, PMOT39, PASeT1 and PASeT2 are 1.87, 1.87, 1.86 and 1.97 eV, respectively.

[0150] After blending with ITIC-2F, the absorption of the blended films of the three polymer materials showed significant differences: the characteristic absorption peak of ITIC-2F in the PMTT56:ITIC-2F and PMOT39:ITIC-2F blended films was weak, while the characteristic absorption peak of ITIC-2F in the PASeT1:ITIC-2F blended film was more balanced with the characteristic absorption peak of the polymer, indicating that PASeT1 and ITIC-2F have better blending compatibility. The better absorption performance of the PASeT1:ITIC-2F blend system is expected to enable the material system to obtain better photocurrent and thus higher photovoltaic performance.

[0151] according to Figure 3It can be concluded that the HOMO / LUMO energy levels of PMTT56, PMOT39, PASeT1 and PASeT2 are 5.39eV / 3.40eV, 5.34eV / 3.38eV, 5.41eV / 3.40eV and 5.36eV / 3.38eV, respectively. Compared with the MOT polymer PMOT39, the AST polymer PMTT56 and the ASeT polymer PASeT1 exhibit deeper HOMO energy levels. The LUMO energy level difference between the polymer and ITIC-2F is greater than 0.3eV, which is conducive to the effective exciton splitting at the donor-acceptor interface. The deeper HOMO energy level of the polymer is conducive to the polymer material to obtain a higher open circuit voltage in photovoltaic devices.

[0152] Test Example 2

[0153] The photovoltaic devices prepared in the corresponding use cases 1-3 and comparative application example 1 were subjected to performance tests.

[0154] Test method:

[0155] 1. Under AM1.5G solar simulator lighting (100mW cm -2 ) was used to measure the current-voltage curve of the device in air using a Keithley 2400 source measurement device. The external quantum efficiency (EQE) was measured at room temperature using a quantum efficiency system (QE-R). The light source was a bromine tungsten lamp.

[0156] 2. Considering the excellent solubility of PMTT56:ITIC-2F in chlorobenzene and xylene, the solubility in toluene will not become a limiting factor in processing. In addition, due to the lower boiling point of toluene, the short-circuit current of the device is expected to be improved. Therefore, toluene is further used as a processing solvent to prepare photovoltaic devices, and then the relevant performance is tested. The morphology of the PMTT56:ITIC-2F blend film is further studied by transmission electron microscopy (TEM) and atomic force microscopy (AFM).

[0157] The test results are as follows Figure 4-Figure 7 And as shown in Table 2.

[0158] Figure 4 shows the current-voltage curve (JV) diagram of photovoltaic devices based on different polymer materials;

[0159] in,

[0160] Figure 4 (a) is the current-voltage curve (JV) of PMTT56:ITIC-2F photovoltaic device;

[0161] Figure 4(b) is the current-voltage curve (JV) of PMOT39:ITIC-2F photovoltaic device;

[0162] Figure 4 (c) Current-voltage curve (JV) of PMSeT1:ITIC-2F and PMSeT2:ITIC-4F photovoltaic devices.

[0163] Figure 5 The external quantum efficiency curve (EQE) of photovoltaic devices based on different polymer materials is shown;

[0164] in,

[0165] Figure 5 (a) is the external quantum efficiency curve of PMTT56:ITIC-2F photovoltaic device in different solvents;

[0166] Figure 5 (b) is the external quantum efficiency curve of PMOT39:ITIC-2F photovoltaic device;

[0167] Figure 5 (c) is the external quantum efficiency curve of PMSeT1:ITIC-2F and PMSeT2:ITIC-4F photovoltaic devices.

[0168] Figure 6 TEM images of hybrid films prepared based on PMTT56:ITIC-2F are shown;

[0169] in,

[0170] Figure 6 (a) Film treated with toluene and 1% DPE;

[0171] Figure 6 (b) Film treated with o-xylene and 1% DPE;

[0172] Figure 6 (c) Film treated with chlorobenzene and 1% DPE.

[0173] Figure 7 AFM images of hybrid films prepared based on PMTT56:ITIC-2F are shown (size: 5 μm×5 μm);

[0174] in,

[0175] Figure 7 (a) Film treated with toluene and 1% DPE;

[0176] Figure 7 (b) Film treated with o-xylene and 1% DPE;

[0177] Figure 7(c) Film treated with chlorobenzene and 1% DPE.

[0178] Table 2 shows the performance of photovoltaic devices with different structures.

[0179] Table 2 Photovoltaic device performance based on different polymers

[0180]

[0181] In this test example, chlorobenzene was first used to prepare photovoltaic devices, and a chlorobenzene solution (concentration of 8 mg / mL) of polymer:acceptor was prepared by spin coating to prepare the active layer. In the device prepared by chlorobenzene, PMTT56 achieved a photoelectric conversion efficiency of 11.17%, of which J sc =17.76mAcm -2 , V oc =0.935V, FF=67.3%. It is worth mentioning that due to the deeper HOMO energy level of PMTT56, PMTT56 obtained a larger open circuit voltage of 0.94V compared with PMOT39. It is generally believed that the open circuit voltage is linearly related to the difference between the HOMO energy level of the donor and the LUMO energy level of the acceptor. Then, xylene, a non-chlorine solvent commonly used in the preparation of organic optoelectronic devices, was used as a processing solvent to prepare photovoltaic devices. Low-polarity conjugated polymer materials have good solubility in xylene. The PMTT56 / ITIC-2F blended film obtained by spin coating from a xylene solution has very good uniformity, indicating that the blended system has good film-forming properties in a xylene solution. However, due to a slight decrease in the short-circuit current (which may be due to the higher boiling point of xylene resulting in a lower spin-coated film thickness), the photoelectric conversion efficiency of the device processed with xylene decreased slightly.

[0182] from Figure 4 It can be seen that the photovoltaic device prepared in toluene solution maintains the very high open circuit voltage of PMTT56:ITIC-2F, while greatly improving the short circuit current.

[0183] according to Figure 6 It can be seen that the PMTT56:ITIC-2F blend film exhibits a very flat morphology. Figure 7 It can be seen that its surface roughness is less than 1.5nm. Based on the good morphology, the PMTT56:ITIC-2F device prepared in toluene obtained a photoelectric conversion efficiency of 12.41%.

[0184] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0185] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A donor-acceptor polymer, characterized in that The group in the donor-acceptor polymer includes a 4-alkylthiothiophene ring attached as a conjugated side chain to the main chain of the donor-acceptor polymer; The donor is selected from the following structures: Wherein, R1 is selected from -(CH2) m H、-O(CH2) m H and -S(CH2) m One or more of H, m is selected from an integer in the range of 1 to 20; The two sides of the receptor have a group consisting of unsubstituted or alkyl-substituted thiophene or a derivative of unsubstituted or alkyl-substituted thieno[2,3-b]thiophene as a bridging group; The receptor is selected from the following structures: Wherein, R2 is selected from H, CH3, C2H5, C4H9, C6H 13 、C8H 17 , C 12 H 25 , 2-hexyldecyl or 2-octyldodecyl; Wherein, the acceptor aromatic ring is selected from the following structures: Wherein, R is selected from hydrogen atom, -CH3, -C2H5, -C4H9, -C6H 13 、-C8H 17 , -C 12 H 25 , 2-hexyldecyl or 2-octyldodecyl.

2. A composition, characterized in that The invention comprises a blend consisting of the donor-acceptor polymer according to claim 1 and a fullerene derivative or a non-fullerene derivative.

3. The composition according to claim 2, characterized in that The non-fullerene derivative is selected from one of ITIC-2F and ITIC-4F.

4. The method for preparing the donor-acceptor polymer according to claim 1, characterized in that: The steps include: Preparation method of 4-alkylthiothiophene ring: 3-bromo-2-(2-ethylhexyl)thiophene is added to a solvent, cooled at low temperature, and then an n-butyl lithium solution is added under an inert gas atmosphere. After stirring, 1,2-dimethyldisulfane is added. After stirring for reaction, the reaction is quenched with water and then purified to obtain the 4-alkylthiothiophene ring.

5. A photovoltaic device, characterized in that: Comprising the composition as claimed in claim 2.

Images