CN104086561A - Soluble organic photovoltaic micromolecule material with high fill factor, preparation method and application of material - Google Patents

Abstract

The invention discloses a solution-processable soluble photovoltaic small molecule with a high filling factor, a preparation method and an application thereof, belonging to the field of photovoltaic materials. This type of molecule uses two-dimensionally conjugated benzodithiophene or naphthodithiophene as the donor, and cyanoalkyl ester or oxoalkylcyanide as the acceptor. Such soluble organic small molecule materials are simple to prepare, easy to purify, have good crystallinity, and they have good solubility in common organic solvents (such as dichloromethane, trichloromethane, tetrahydrofuran or chlorobenzene, etc.), and can High-quality films are produced by solution; molecular weights are well defined relative to polymers, and there are no molecular weight distribution issues. Such small molecules are used as donor materials for solar cells, with energy conversion efficiencies of 7.5% and fill factors exceeding 70%.

Description

A kind of soluble organic photovoltaic small molecule material with high filling factor, preparation method and use thereof

technical field

The invention belongs to the technical field of photovoltaic materials, and relates to a soluble organic photovoltaic small molecule material, a preparation method and its application, in particular to a soluble organic photovoltaic small molecule material with a high filling factor, a preparation method and its application. the

Background technique

In recent years, solution-processable organic small molecule solar cells have received special attention because of their advantages such as simple preparation process, low cost, light weight, flexible devices, and clear molecular structure and no molecular weight distribution of polymer solar cells ( (a) A. Mishra, P. Bauerle, Angew. Chem. Int. Ed. 2012, 51, 2020-2067. Y. Lin, Y. Li, X. Zhan, Chem. Soc. Rev. 2012, 41, 4245 -4272; (b) V. Gupta, A.K.K. Kyaw, D.H. Wang, S. Chand, G.C. Bazan, A.J. Heeger, Scientific Reports 2013, 3; (c) C.J. Takacs, Y. Sun, G.C. Welch, L.A. Perez, X. Liu , W. Wen, G.C. Bazan, A.J. Heeger, J. Am. Chem. Soc. 2012, 134, 16597-16606.). The triphenylamine series has received extensive attention due to its good solubility and its three-dimensional structure is conducive to the transport of charges in the vertical direction of the device (J. Roncali, Acc. Chem. Res. 2009, 42, 1719-1730.). However, due to the non-planarity of triphenylamine molecules, the intermolecular stacking is not conducive to accumulation, which leads to low charge extraction ability from the blend interface, and the morphology of the blended active layer is not ideal, so the fill factor of the device is low, basically below 60%. The photoelectric conversion efficiency has not broken through 5% until now, and there are only few literature reports exceeding 4% ((a) D. Deng, S. Shen, J. Zhang, C. He, Z. Zhang, Y. Li, Org .Electron.2012,13,2546-2552.(b)H.Shang,H.Fan,Y.Liu,W.Hu,Y.Li,X.Zhan,Adv.Mater.2011,23,1554-1557. (c) J. Min, Y.N. Luponosov, A. Gerl, M.S. Polinskaya, S.M. Peregudova, P.V. Dmitryakov, A.V. Bakirov, M.A. Shcherbina, S.N. Chvalun, S. Grigorian, N. Kaush-Busies, S.A. Ponomarenko, T. Ameri, C.J. Brabec, Adv. Energy Mater. 2013, 10.1002/aenm. 201301234. (d) J. Zhang, D. Deng, C. He, Y. He, M. Zhang, Z.-G. Zhang, Z. Zhang, Y . Li, Chem. Mater. 2011, 23, 817-822.). Therefore, soluble organic photovoltaic small molecule materials with high fill factor are an approach to be investigated in this field. the

Contents of the invention

In view of the problems in the prior art, one of the objectives of the present invention is to provide a soluble organic photovoltaic small molecule material with a high filling factor, the organic photovoltaic small molecule material is composed of di Two-dimensional conjugated benzodithiophene or two-dimensional conjugated naphthodithiophene is the core, and the two ends are symmetrically connected with cyanoester group or oxocyano unit. the

In order to achieve the above object, the present invention adopts following technical scheme:

A kind of soluble organic photovoltaic small molecule material with high fill factor, it has the structure shown in formula (II):

Among them, R ₁ is selected from straight-chain or branched-chain alkyl groups with 6 to 8 carbon atoms (such as 6, 7 or 8), and R ₂ , R ₃ and R ₄ are all independently selected from the group with 6 carbon atoms. ~8 (for example, 6, 7 or 8) linear alkyl groups, m is the number of π bridge thiophenes, m is any natural number from 1 to 3, such as 1, 2, or 3, preferably 2 to 3.

An exemplary soluble organic photovoltaic small molecule material with a high fill factor has the following structure:

Wherein, R ₁ is selected from straight-chain or branched-chain alkyl groups with 6 to 8 carbon atoms (such as 6, 7 or 8), R ₂ and R ₃ are independently selected from 6 to 8 carbon atoms ( Such as 6, 7 or 8) straight-chain alkyl group, m is the number of π bridge thiophenes, m is any natural number from 1 to 3, such as 1, 2 or 3, preferably 2 to 3.

The structure of benzodithiophene and naphthodithiophene with thiophene/nathiophene/benzene ring has a large π-conjugated coplanar structure, moderate electron donating ability, and good air stability. It is an important component of high-efficiency photovoltaic materials. Structural units. The cyanoester and oxocyano acceptor units are simple in structure, good in planarity, and their solubility can be adjusted through the alkyl chain. The present invention uses two-dimensional conjugated benzodithiophene or naphthodithiophene as a donor, and cyanoalkyl ester or oxoalkylcyanide as an acceptor. The donor unit and the acceptor with good planarity Units (especially oxoalkylcyanides are introduced into photovoltaic small molecules for the first time) are applied to solution-processable photovoltaic small molecules, and solution-processable organic photovoltaic small molecules with good planarity, good crystallinity, and high efficiency are prepared. Such soluble organic photovoltaic small molecule materials are simple to prepare, easy to purify, have good crystallinity, and they have good solubility in common organic solvents (such as dichloromethane, chloroform, tetrahydrofuran and chlorobenzene, etc.), High-quality thin films can be prepared by solution methods. Furthermore, the molecular weight is clear for the polymer, and there is no problem of molecular weight distribution. When the organic photovoltaic small molecule material of the present invention is used as a donor material of a solar cell, the energy conversion efficiency reaches 7.5%, and the filling factor exceeds 70%. the

The second object of the present invention is to provide a method for preparing a soluble organic photovoltaic small molecule material with a high fill factor as described above, said method comprising the steps of:

Compound shown in formula (III), catalyzer, organic solvent and compound shown in formula (IV) are mixed and reflux reaction obtains compound shown in formula (II);

or,

The compound represented by the formula (III), catalyst, organic solvent and the compound represented by the formula (V) are mixed and refluxed to obtain the compound represented by the formula (II). the

in,

R ₁ is selected from straight-chain alkyl groups or branched-chain alkyl groups with 6 to 8 carbon atoms, R ₂ , R ₃ and R ₄ are all independently selected from straight-chain alkyl groups with 6 to 8 carbon atoms, and m is Any natural number from 1 to 3.

Preferably, the molar ratio of the compound shown in formula (III) to the compound shown in formula (IV) is 1:2 to 1:10, such as 1:2.5, 1:3, 1:3.5, 1:4, 1: 4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9 or 1:9.5, preferably 1:10. the

Preferably, the molar ratio of the compound shown in formula (III) to the compound shown in formula (V) is 1:2 to 1:10, such as 1:2.5, 1:3, 1:3.5, 1:4, 1: 4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9 or 1:9.5, preferably 1:10. the

Preferably, the reaction temperature is 30-80°C, such as 34°C, 38°C, 42°C, 46°C, 50°C, 54°C, 58°C, 62°C, 66°C, 70°C, 74°C or 78°C , preferably 80°C. the

Preferably, the reaction time is 12 to 48 hours, such as 15 hours, 18 hours, 21 hours, 24 hours, 27 hours, 30 hours, 33 hours, 36 hours, 39 hours, 42 hours, 45 hours or 47 hours , preferably 12 hours. the

Preferably, the catalyst is any one or a mixture of at least two of triethylamine, pyridine, piperidine or potassium tert-butoxide. Said mixture is for example the mixture of triethylamine and pyridine, the mixture of triethylamine and piperidine, the mixture of triethylamine and potassium tert-butoxide, the mixture of pyridine, piperidine and potassium tert-butoxide, triethylamine, pyridine, Mixture of piperidine and potassium tert-butoxide. the

Preferably, the organic solvent is any one or a mixture of at least two of chloroform, toluene or chlorobenzene. The mixture is, for example, a mixture of chloroform and toluene, a mixture of chloroform and chlorobenzene, a mixture of toluene and chlorobenzene, a mixture of chloroform, toluene and chlorobenzene. the

Preferably, the method also includes the following purification steps:

The organic matter containing the compound represented by formula (V) was dissolved in diethyl ether and 1N hydrochloric acid with a volume ratio of 3:1, washed and extracted with a saturated aqueous solution of sodium chloride, dried over anhydrous magnesium sulfate, and evaporated in vacuo to remove the solvent. The mixed solvent of petroleum ether and ethyl acetate with a volume ratio of 4:1 was purified by chromatographic silica gel column. the

Preferably, the solution containing the compound shown in the formula (II) is cooled to room temperature, then methanol is added for precipitation, the precipitate is collected by centrifugation, and then the mixed solvent of sherwood oil and chloroform with a volume ratio of 2:3 is passed through a chromatographic silica gel column For purification, after evaporating the solvent in vacuo, adding chloroform and methanol, recrystallizing, and collecting the precipitate by filtration, the compound represented by formula (II) is obtained. the

Preferably, the preparation method of compound shown in formula (III), comprises the following steps:

Under the catalysis of a palladium catalyst, the compound represented by the formula (VI) and the compound represented by the formula (VII) are reacted under an inert atmosphere to obtain the compound represented by the formula (III). the

Wherein, _R1 is selected from straight-chain alkyl groups or branched-chain alkyl groups with 6-8 carbon atoms, _R3 and _R4 are independently selected from straight-chain alkyl groups with 6-8 carbon atoms, and m is 1 Any natural number of ~3, such as 1, 2, or 3, preferably 2-3.

Preferably, the palladium catalyst is tetrakis(triphenylphosphine)palladium. the

Preferably, the molar ratio of the palladium catalyst to the compound represented by formula (VII) is 0.02 to 0.05:1, such as 0.022:1, 0.024:1, 0.026:1, 0.028:1, 0.03:1, 0.032:1 , 0.034:1, 0.036:1, 0.038:1, 0.04:1, 0.042:1, 0.044:1, 0.046:1 or 0.048:1, preferably 0.02:1. the

Preferably, the molar ratio of the compound shown in formula (VI) and formula (VII) is: 1:2～1:3, such as 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8 or 1:2.9, preferably 1:2. the

Preferably, the reaction temperature of the reaction is 100-120°C, such as 101°C, 102°C, 103°C, 104°C, 105°C, 106°C, 107°C, 108°C, 109°C, 110°C, 111°C, 112°C °C, 113°C, 114°C, 115°C, 116°C, 117°C, 118°C or 119°C, preferably 100°C. the

Preferably, the reaction time of the reaction is 12 to 48 hours, such as 15 hours, 18 hours, 21 hours, 24 hours, 27 hours, 30 hours, 33 hours, 36 hours, 39 hours, 42 hours, 45 hours or 47 hours. hours, preferably 12 hours. the

Preferably, the reaction is carried out in an organic solvent, and the organic solvent is specifically any one or a mixture of at least two of toluene, chlorobenzene or o-dichlorobenzene. The mixture is, for example, a mixture of toluene and chlorobenzene, a mixture of toluene and o-dichlorobenzene, a mixture of chlorobenzene and o-dichlorobenzene, a mixture of toluene, chlorobenzene and o-dichlorobenzene. the

Preferably, the method comprises the following purification steps:

The solution containing the compound shown in formula (III) and formula (VII) was cooled to room temperature, then dissolved in dichloromethane, then washed and extracted with a saturated aqueous solution of sodium chloride, dried over anhydrous magnesium sulfate, and the solvent was evaporated in vacuo Afterwards, the mixed solvent of petroleum ether and dichloromethane with a volume ratio of 1:2 was used for purification on a chromatographic silica gel column. the

Preferably, the preparation method of compound shown in formula (IV) comprises the steps:

At -78°C, add butyllithium to the mixed solution of cyanoacetic acid and bipyridine in tetrahydrofuran until the solution turns water red, then raise the temperature to -10°C, and keep adding butyllithium during the heating process to maintain the solution The color is water red, then drop to -78°C and add the acid chloride corresponding to the alkyl group, and react for half an hour. the

Preferably, the method also includes the following purification steps:

Pour the mixed solution of diethyl ether and 1N hydrochloric acid into the reaction solution, then wash with aqueous sodium chloride, dry over anhydrous magnesium sulfate, evaporate the solvent in vacuo, and use a mixed solvent of petroleum ether and ethyl acetate with a volume ratio of 1:4 Purify through chromatographic silica gel column to obtain light yellow liquid, which is the compound represented by formula (IV). the

The preparation method of compound shown in exemplary formula (II) comprises the steps:

At -78°C, add butyllithium to the mixed solution of cyanoacetic acid and bipyridine in tetrahydrofuran until the solution turns watery red, then raise the temperature to -10°C, and keep adding butyllithium during the heating process to maintain the color of the solution It is water red, and then drop to -78°C to add the acid chloride corresponding to the alkyl group, and react for half an hour. Pour diethyl ether and 1N hydrochloric acid into the reaction solution, then wash with aqueous sodium chloride, dry over anhydrous magnesium sulfate, and evaporate the solvent in vacuo, then use a mixed solvent of petroleum ether and ethyl acetate with a volume ratio of 1:4 to pass through silica gel. Column purification to obtain a light yellow liquid. Then it was added to the dry chloroform solution of the compound of formula (III), then potassium tert-butoxide and pyridine were added in a catalytic amount, and the reaction was refluxed for 12 hours, followed by precipitation with methanol, washing with aqueous sodium chloride solution, anhydrous sulfuric acid Dry magnesium, evaporate the solvent in vacuo, use a mixed solvent of petroleum ether and chloroform with a volume ratio of 2:3 to pass through a chromatographic silica gel column for purification, evaporate the solvent in vacuo, add chloroform and methanol, recrystallize, and collect the precipitate by filtration , to obtain a black solid, namely to obtain the compound represented by formula (II). the

The third object of the present invention is to provide a use of a soluble organic photovoltaic small molecule material with a high fill factor as described above, which is used for the preparation of photovoltaic devices, preferably for the preparation of organic solar cells, and more preferably for the preparation of organic solar cells. Donor material for batteries. the

In the present invention, the high fill factor means that the fill factor is greater than 70%. the

Compared with prior art, the present invention has following beneficial effect:

In the present invention, the donor unit, the acceptor unit and the π bridge unit with a good planar structure are applied to the design and synthesis of soluble organic photovoltaic small molecules, and a series of crystalline small molecules with good planarity are obtained, and a new acceptor oxygen with planarity is synthesized for the first time. Substituted alkyl cyano groups and applied them to photovoltaic materials. In addition, the present invention synthesized two-dimensional conjugated benzodithiophene and two-dimensional conjugated naphthodithiophene with thiophene/nathiophene/benzene conjugated branched chain as the core, and symmetrically connected cyanoester groups or oxygen at both ends. Soluble organic photovoltaic small molecules with cyano units. They have good solubility in common organic solvents (such as chloroform, tetrahydrofuran, toluene), and high-quality films can be prepared by solution spin coating. At the same time, these soluble molecules have good accumulation in the film. The absorption of the film is red-shifted by 90nm relative to the solution, and it also has relatively good crystallinity and matched HOMO and LUMO energy levels. the

Using organic photovoltaic small molecules as donors and PC ₆₀ BM or PC ₇₀ BM as acceptors, bulk heterojunction organic solar cells were prepared. The optimized energy conversion efficiency can reach 7.5%, and the fill factor exceeds 70%.

Description of drawings

Fig. 1 is the ultraviolet-visible absorption spectrum diagram of M1 in chloroform solution and film state. the

Fig. 2 is the ultraviolet-visible absorption spectrum diagram of M2 in chloroform solution and film state. the

Figure 3 shows the oxidation potential of M1 measured by electrochemical method. the

Fig. 4 is the cyclic voltammetry curve measured by M2 electrochemical method. the

Fig. 5 shows the IV curve of the soluble organic small molecule solar cell device with the structure ITO/PEDOT:PSS/M1:PC ₇₀ BM/Ca/Al.

Fig. 6 shows the IV curve of the soluble organic small molecule solar cell device with the structure ITO/PEDOT:PSS/M2:PC ₇₀ BM/Ca/Al.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and through specific implementation methods. the

The experimental methods described in the following examples, unless otherwise specified, are conventional methods; the reagents and materials, unless otherwise specified, can be obtained from commercial sources. the

Example 1. Synthesis of BDTT (compound of R ₁ =C ₂ H ₄ C ₆ H ₁₃ in formula III)

The chemical reaction process is as follows (references for specific reaction steps and reaction conditions LijunHuo, Angew.Chem.Int.Ed.2011, 50, 9697-9702) 

Embodiment 2, BrSCHO (compound 10)

The chemical reaction process is as follows (specific reaction steps and reaction conditions refer to J.Zhou, X.Wan, Y.Liu, G.Long, F.Wang, Z.Li, Y.Zuo, C.Li, Y.Chen , Chem. Mater. 2011, 23, 4666-4668.). the

Embodiment 3, B3SCHO2BDTT (compound 11)

The chemical reaction process is as follows (specific reaction steps and reaction conditions refer to J.Zhou, Y.Zuo, X.Wan, G.Long, Q.Zhang, W.Ni, Y.Liu, Z.Li, G.He , C. Li, B. Kan, M. Li, Y. Chen, J. Am. Chem. Soc. 2013, 135, 8484-8487.). the

The feed ratio of compound 6 and compound 10 is 1:2, the reaction temperature is 100°C, the reaction time is 12 hours, the amount of palladium catalyst is 2% of the molar equivalent of compound 10, and the product 11 is obtained as a maroon solid with a yield of 80% . the

In addition, the reaction conditions can also be: the feed ratio of compound 6 and compound 10 is 1:2, the amount of palladium catalyst is 2% of the molar equivalent of compound 10, the reaction temperature is 100 ° C, the reaction time is 48 hours, and the product 11 is jujube Red solid, yield 78%. the

In addition, the reaction conditions can also be: the feed ratio of compound 6 and compound 10 is 1:2, the amount of palladium catalyst is 2% of the molar equivalent of compound 10, the reaction temperature is 120 ° C, the reaction time is 48 hours, and the product 11 is jujube Red solid, yield 79%. the

In addition, the reaction conditions can also be: the feed ratio of compound 6 and compound 10 is 1:2, the amount of palladium catalyst is 5% of the molar equivalent of compound 10, the reaction temperature is 100 ° C, the reaction time is 12 hours, and the product 11 is jujube Red solid, yield 79%. the

In addition, the reaction conditions can also be: the feed ratio of compound 6 and compound 10 is 1:3, the amount of palladium catalyst is 2% of the molar equivalent of compound 10, the reaction temperature is 100 ° C, the reaction time is 12 hours, and the product 11 is obtained as jujube Red solid, yield 82%. the

The synthesis of embodiment 4, M1

The chemical reaction process is shown below, and the specific reaction steps and reaction conditions are as follows: under an inert atmosphere, two drops of dry triethylamine were added to a solution of compound 11 (364mg, 0.23mmol) in dry CHCl ₃ (30ml), and then octyl Cyanoethyl ester (455.7 mg, 2.3 mmol). The whole reaction system was heated to 80°C and stirred for 12 hours. After the reaction liquid was cooled down, methanol was added for precipitation, centrifuged, and the solid part was dissolved with chloroform, washed with water three times, and dried over anhydrous magnesium sulfate. The solvent was removed by rotary evaporation of the organic phase, petroleum ether: chloroform = 2:3 (volume ratio) was used as eluent, and the product was separated by silica gel chromatography. The product was recrystallized from chloroform and methanol, chloroform and n-hexane to obtain a black solid product (200 mg, 45%).

Alternatively, the ratio of compound 11 and octylcyanoethyl ester was adjusted to 1:2, and other conditions remained unchanged, to obtain 89 mg of a black solid product with a yield of 20%. the

Alternatively, the reaction time was extended to 48 hours, and other conditions remained unchanged to obtain 200 mg of a black solid product with a yield of 45%. the

Alternatively, the reaction temperature of the system was lowered to room temperature 30° C., and other conditions remained unchanged, to obtain a black solid product with a yield of 130 mg and a yield of 29%. the

Alternatively, the reaction temperature of the system was lowered to room temperature 30° C., and the reaction time was extended to two days to obtain a black solid product with a yield of 178 mg and a yield of 40%. the

MALDI–TOF MS: m/z 1933.1, ¹ H NMR (400MHz, CHCl ₃ ): 8.20 (s, 2H), 7.60-7.64 (d, 4H), 7.30-7.32 (m, 4H), 7.14-7.15 ( m,4H),6.9-6.97(m,2H),4.27-4.31(t,4H),2.77-2.86(m,12H),1.70-1.75(m,14H),1.27-1.38(m,12H), 1.36(m,76H),0.85-0.98(m,30H).Elemental Anal calcd for:C,70.76;H,7.92;N,1.45;O,3.31;S,16.57.

The preparation method of small molecules of other terminal acceptor cyanoethyl esters is the same as above. the

The synthesis of embodiment 5, M2

The chemical reaction process is shown below, and the specific reaction steps and reaction conditions are as follows: under an inert atmosphere, 3-oxoundecyl cyanide (364mg, 2mmol) was added to compound 11 (300mg, 0.19mmol) and pyridine (0.2mL, 2.5mmol) was dried in CHCl ₃ (30ml), and then potassium tert-butoxide (11mg, 0.1mmol) was added. The whole reaction system was heated to 80°C and stirred for 12 hours. After the reaction liquid was cooled down, methanol was added for precipitation, centrifuged, and the solid part was dissolved with chloroform, washed with water three times, and dried over anhydrous magnesium sulfate. The solvent was removed by rotary evaporation of the organic phase, petroleum ether: chloroform = 2:3 (volume ratio) was used as eluent, and the product was separated by silica gel chromatography. The product was recrystallized from chloroform, methanol, and dichloromethane to obtain a black solid product (170 mg, 46.8%).

Alternatively, the ratio of compound 11 and 3-oxoundecylcyanide was adjusted to 1:2, and other conditions remained unchanged, to obtain 69 mg of a black solid product with a yield of 19%. the

Alternatively, the reaction time was extended to 48, and other conditions remained unchanged to obtain 170 mg of a black solid product with a yield of 46.8%. the

Alternatively, the reaction temperature of the system was lowered to room temperature 30° C., and other conditions remained unchanged, to obtain 110 mg of a black solid product with a yield of 30.2%. the

Alternatively, the reaction temperature of the system was lowered to room temperature 30° C., and the reaction time was extended to two days to obtain a black solid product with a yield of 153 mg and a yield of 42%. the

MALDI–TOF MS: m/z1900.7.1H NMR (400MHz, CHCl3): 8.16 (s, 2H), 7.62 (s, 4H), 7.31 (m, 4H), 7.13 (m, 4H), 6.96 (m, 2H),2.86(m,16H),1.83(m,2H),1.68(m,12H),1.36(m,76H),1.18(m,30H).13C NMR(101MHz,CDCl3)δ192.60,146.52,145.13 ,142.89,140.99,140.40,139.79,137.53,136.44,135.51,134.90,133.37,132.43,129.27,127.32,126.96,125.36,124.51,123.42,122.47,118.29,116.94,103.53,40.53,39.61,33.39,31.57,30.88 ,30.84,30.81,30.57,29.43,29.33,29.18,28.69,28.61,28.50,28.43,28.38,28.33,28.25,28.22,28.12,27.98,24.89, 23.07,22.05,21.6145,933.9

The preparation method of small molecules of other terminal oxoalkyl cyanides is the same as above. the

The preparation methods of other compounds M3～M10 are basically the same as above, and the specific reaction process is as follows:

Embodiment 6,3-oxo undecyl cyanide (compound 13)

The chemical reaction process is shown below, and the specific reaction steps are as follows: Under an inert atmosphere at -78°C, n-BuLi (2.4M in hexane) was added dropwise to cyanoacetic acid (2g, 23.5mmol), bipyridine (ca. 20mg), and dried tetrahydrofuran (300 mL) until the color of the mixture turned pink, indicating a slight excess of butyllithium. Then the temperature was raised to -10°C, and n-butyllithium was continued to be added dropwise during the heating process to ensure that the solution was pink (the amount of butyllithium used was about 19.6mL), and then the entire reaction system was lowered to -8°C. Then nonanoyl chloride (1.4g, 11.7mmol) was added to the reaction solution and kept stirring at -78°C for 0.5h. The reaction solution was poured into a mixed solution of 360mL ether and 120mL 1mol/L hydrochloric acid. The organic phase was washed three times with brine and water respectively, and dried over anhydrous magnesium sulfate. The organic phase was rotatably evaporated to remove the solvent, using petroleum ether:ethyl acetate=4:1 (volume ratio) as eluent, and separated by silica gel chromatography to obtain the target product (1.84g, 86%).MS (EI):m /z182.0.1H NMR (400MHz, _CHCl3 ): 3.14 (s, 2H), 2.60 (t, 2H), 1.62 (m, 2H), 1.26 (m, 10H), 0.87 ( ^t , 3H).

The preparation method of other 3-oxoalkyl cyanides is the same as above. the

Embodiment 7, measure the ultraviolet-visible absorption spectrum of small molecule in chloroform solution and film state and utilize empirical formula to calculate the optical bandgap of polymer

An appropriate amount of small molecule M1 was dissolved in chloroform to prepare a solution with a certain concentration, and part of the solution was spin-coated on a quartz plate to form a polymer film. the

The ultraviolet-visible absorption spectra of M1 measured in chloroform solution and film state are shown in Fig. 1 . The optical band gap of the polymer is calculated using the formula (E _g =1240/λ absorption margin), wherein the maximum absorption peak of M1 in chloroform solution is 496nm, and the film has a wide absorption at 300-700nm, and the maximum absorption peak is 570nm, The absorption edge is at 690nm and the optical bandgap is 1.80eV, indicating that this is a narrow bandgap organic semiconductor polymer. Moreover, the maximum absorption peak of the film is red-shifted by 75nm relative to the solution, indicating that the molecules have good planarity and are well aggregated in the film.

The test methods for other small molecules M2-M10 are basically the same as above. the

Embodiment 8, measure the cyclic voltammetry curve under the state of small molecular film

Figure 3 and Figure 4 are the cyclic voltammograms based on the M1 and M2 films. The chloroform solution of M2/M1 was coated on the platinum electrode, and Ag/Ag ⁺ was used as the reference electrode, and after drying to form a film, it was placed in the acetonitrile solution of tetrabutylammonium hexafluorophosphate for measurement. From the initial oxidation potential and initial reduction potential obtained from the figure, then by the formula E _HOMO =-e(E ^ox _onset +4.71)(eV)=-5.19eV, E _LUMO =-e(E ^red _onset +4.71) (eV)=-3.46eV The HOMO of M1/M2 is calculated to be -5.11, -5.18eV, and the LUMO is -3.44, -3.47eV respectively.

The testing methods for other small molecules are basically the same as above. the

Photovoltaic property test of embodiment 9, M1 and M2

Organic solar cells were prepared by solution spin coating with M2 as donor and PC ₇₀ BM as acceptor.

The device structure is ITO/PEDOT:PSS/M2:PC ₇₀ BM/Ca/Al.

The preparation method is as follows: M2 is blended with the same mass of PC ₇₀ BM (M2:PC ₇₀ BM mass ratio is 1.5:1), and dissolved in chloroform to obtain a 10 mg/mL solution. Organic solar cells were fabricated on transparent silver tin oxide (ITO)-coated glass substrates. The transparent conductive glass with ITO was ultrasonically cleaned with deionized water, acetone, and isopropanol for 15 minutes, and then the surface of the substrate was treated with ozone, and PEDOT:PSS was spin-coated on the ITO, and the spin-coating speed was 2000- 6000 rpm, and dried at 150° C. for 15 minutes to obtain an anode modification layer with a thickness of 30 nm. In the glove box, the chloroform solution of the polymer and [6,6]-phenyl C ₇₀ butyrate methyl ester (PC ₇₀ BM) was evenly spin-coated on the anode modification layer at a speed of 600-4000 rpm , to obtain an active material layer with a thickness of 80-150 nm. Finally, Ca is evaporated onto the active material layer under a vacuum of 2×10 ^-6 Torr to form a cathode modification layer with a thickness of 20 nm; and Al is evaporated to the cathode modification layer under a vacuum of 2×10 ^-6 Torr. layer, a cathode with a thickness of 100 nm was formed to obtain a polymer solar cell device. Use a combination of 500W xenon lamp and AM1.5 filter as a white light source to simulate sunlight, adjust the light intensity at the device measurement point to 100mW/cm ^-2 , use Keithley to measure the open circuit voltage and short circuit of the prepared polymer solar cell device The three parameters of current and fill factor are tested. Figures 5 and 6 are the current-voltage curves of devices based on molecules M1 and M2, respectively. The open circuit voltage of M1 is 0.97V, the short circuit current is 10.1mA/cm ² , the fill factor is 73%, the photoelectric conversion efficiency is 7.48%; the open circuit voltage of M2 is 0.92V, the short circuit current is 10.4mA/cm ² , the fill factor is 68%, and the photoelectric conversion efficiency is 6.4%.

The test methods for other small molecules are basically the same as above, and the acceptor material is PC ₇₀ BM or PC ₆₀ BM.

The applicant declares that the present invention illustrates the detailed methods of the present invention through the above-mentioned examples, but the present invention is not limited to the above-mentioned detailed methods, that is, it does not mean that the present invention must rely on the above-mentioned detailed methods to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection and disclosure of the present invention. the

Claims (10)

1. A soluble organic photovoltaic small molecule material, which has a structure as shown in formula (II): Wherein, R ₁ is selected from straight-chain alkyl groups or branched-chain alkyl groups with 6-8 carbon atoms, R ₂ , R ₃ and R ₄ are all independently selected from straight-chain alkyl groups with 6-8 carbon atoms, m is any natural number of 1-3. 2. a preparation method of soluble organic photovoltaic small molecule material as claimed in claim 1, is characterized in that, described method comprises the steps: The compound shown in formula (III), catalyst, organic solvent and the compound shown in formula (IV) are mixed and refluxed to obtain the compound shown in formula (II); or, The compound shown in formula (III), catalyst, organic solvent and the compound shown in formula (V) are mixed and refluxed to obtain the compound shown in formula (II); in, R ₁ is selected from straight-chain alkyl groups or branched-chain alkyl groups with 6 to 8 carbon atoms, R ₂ , R ₃ and R ₄ are all independently selected from straight-chain alkyl groups with 6 to 8 carbon atoms, and m is Any natural number from 1 to 3. 3. The method according to claim 2, wherein the molar ratio of the compound shown in formula (III) to the compound shown in formula (IV) is 1:2 to 1:10, preferably 1:10; Preferably, the molar ratio of the compound represented by formula (III) to the compound represented by formula (V) is 1:2 to 1:10, preferably 1:10; Preferably, the reaction temperature is 30-80°C, preferably 80°C. Preferably, the time for the reflux reaction is 12 to 48 hours, preferably 12 hours; Preferably, the catalyst is any one or a mixture of at least two of triethylamine, pyridine, piperidine or potassium tert-butoxide; Preferably, the organic solvent is any one or a mixture of at least two of chloroform, toluene or chlorobenzene. 4. the method as claimed in claim 2 or 3, is characterized in that, described method also comprises following purification steps: The organic matter containing the compound represented by formula (IV) was dissolved in diethyl ether and 1N hydrochloric acid with a volume ratio of 3:1, washed and extracted with a saturated aqueous solution of sodium chloride, dried over anhydrous magnesium sulfate, and evaporated in vacuo to remove the solvent. Purify by using a mixed solvent of petroleum ether and ethyl acetate with a volume ratio of 4:1 through a chromatographic silica gel column; Preferably, the solution containing the compound shown in formula (II) is cooled to room temperature, then methanol is added for precipitation, the precipitate is collected by centrifugation, and then the mixed solvent of petroleum ether and chloroform with a volume ratio of 2:3 is passed through a chromatographic silica gel column For purification, after evaporating the solvent in vacuo, adding chloroform and methanol, recrystallizing, and collecting the precipitate by filtration, the compound represented by formula (II) is obtained. 5. The method according to any one of claims 2-4, wherein the preparation method of the compound shown in formula (III) comprises the steps of: Under the catalysis of a palladium catalyst, the compound shown in the formula (VI) and the compound shown in the formula (VII) react under an inert atmosphere to obtain the compound shown in the formula (III); Wherein, _R1 is selected from straight-chain alkyl groups or branched-chain alkyl groups with 6-8 carbon atoms, _R3 and _R4 are independently selected from straight-chain alkyl groups with 6-8 carbon atoms, and m is 1 ~An arbitrary natural number of 3. 6. the method for claim 5 is characterized in that, described palladium catalyst is tetrakis (triphenylphosphine) palladium; Preferably, the molar ratio of the palladium catalyst to the compound represented by formula (VI) is 0.02-0.05:1, preferably 0.02:1; Preferably, the molar ratio of the compounds represented by formula (VI) and formula (VII) is: 1:2 to 1:3, preferably 1:2; Preferably, the reaction temperature of the reaction is 100-120°C, preferably 100°C; Preferably, the reaction time of the reaction is 12 to 48 hours, preferably 12 hours; Preferably, the reaction is carried out in an organic solvent, and the organic solvent is any one or a mixture of at least two of toluene, chlorobenzene or o-dichlorobenzene; Preferably, the method comprises the following purification steps: The solution containing the compound shown in formula (III) and formula (VII) was cooled to room temperature, then dissolved in dichloromethane, then washed and extracted with a saturated aqueous solution of sodium chloride, dried over anhydrous magnesium sulfate, and the solvent was evaporated in vacuo Afterwards, the mixed solvent of petroleum ether and dichloromethane with a volume ratio of 1:2 was used for purification on a chromatographic silica gel column. 7. The method according to any one of claims 2-6, wherein the preparation method of the compound shown in formula (IV) comprises the steps of: At -78°C, add butyllithium to the mixed solution of cyanoacetic acid and bipyridine in tetrahydrofuran until the solution turns water red, then raise the temperature to -10°C, and keep adding butyllithium during the heating process to maintain the solution The color is water red, then drop to -78°C and add the acid chloride corresponding to the alkyl group, and react for half an hour. 8. method as claimed in claim 7, is characterized in that, described method also comprises following purification step: Pour the mixed solution of diethyl ether and 1N hydrochloric acid into the reaction solution, then wash with aqueous sodium chloride solution, dry over anhydrous magnesium sulfate, and evaporate the solvent in vacuo, then wash with a mixed solvent of petroleum ether and ethyl acetate with a volume ratio of 1:4. Purification by chromatography on a silica gel column to obtain a light yellow liquid, namely the compound represented by formula (IV). 9. A use of the soluble organic photovoltaic small molecule material according to claim 1, characterized in that it is used for preparing photovoltaic devices. 10. The use according to claim 9, characterized in that it is used for the preparation of organic solar cells, preferably for the preparation of donor materials for organic solar cells.