WO2018032945A1 - Benzothiophene (benzoselenophene) modification-containing photoelectric compound, preparation method therefor, and use thereof - Google Patents

Abstract

The present invention relates to a preparation method for a solution processable organic photovoltaic compound using benzothiophene (benzoselenophene) and thiophene (selenophene) as a π bridge, and use thereof, the structural formula of the compound being as represented by formula I. By selecting a suitable organic photoelectric compound of D and A units on the basis of the π bridge, the compound of the present invention has low exciton binding energy and is able to effectively reduce the highest occupied electronic orbital energy level of molecules, thereby making it possible for a high-efficiency material to obtain a high open circuit voltage. As a donor material of an active layer of an organic solar cell, the compound of the present invention has a highest open circuit voltage over 1 V. The compound uses a fluoridized receptor unit as a terminal. The cell energy conversion efficiency of a righted structure of the solar cell exceeds 10%, and the cell energy conversion efficiency of an inverted device structure of the solar cell reaches 11.5% without being subject to any additive or thermal and solvent annealing processing. The compound has important application value.

Description

Photoelectric compound containing thiophene (and selenophene) modification, preparation method and use thereof Technical field

The invention belongs to the field of material chemistry, and particularly relates to a photoelectric compound containing thiophene (and selenophene) and thiophene (selenophene) as a π bridge modification, a preparation method thereof and use thereof.

Background technique

Solar cells are one of the inexhaustible sources of clean energy - one of the effective use of solar energy. Compared with inorganic solar cells, organic solar cells have attracted a lot of attention due to their abundant raw materials, light weight, flexible folding and large-area printing processes. Compared with polymer solar cells, solution-processable organic small-molecule solar cells have developed rapidly in recent years because of their molecular structure. However, there are only a few materials with efficiencies higher than 10%.

Therefore, the molecular structure design can be used to obtain the electrons with the highest occupied orbital (HOMO) energy level, the absorption spectrum is more matched with the solar spectrum, the morphology is more ideal, and the energy conversion efficiency is higher. It is important.

Summary of the invention

In view of the problems of the prior art, it is an object of the present invention to provide a new high efficiency, high open circuit organic photoelectric compound for a solar cell. The above compound of the present invention uses a high mobility of thiophene (and selenophene) and thiophene (selenophene) as a part of a π bridge or a π bridge, and selects appropriate D and A units so that it has low exciton binding energy and is effective. Reducing the highest electron orbital level of the molecule makes it possible to obtain high open circuit voltages for high efficiency materials.

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

An organic photoelectric compound for a solar cell, the structure of which is as shown in the following formula I:

among them,

R ₁ -R ₄ may be independently selected from H, C ₁ -C ₃₀ halo or non-halogenated alkyl, C ₁ -C ₃₀ halo or non-haloalkoxy, C ₁ -C ₃₀ halo or non-halogen substituting mercapto, C ₁ -C ₃₀ haloalkyl or halocycloalkyl, C ₁ -C ₃₀ halogenated or non-halogenated carbonyl group, C ₁ -C ₃₀ halogenated or non-halogenated ester group and a C ₁ -C ₃₀ Any one of a halogenated or non-halogenated sulfone group, wherein R _{1 to} R ₄ may be the same or different. X ₁ and X ₂ may be independently selected from sulfur, oxygen or selenium atoms, wherein X ₁ and X ₂ may be the same or different, D is a donor unit, and A is a receptor unit.

For example, Formula I may specifically be of Formula II:

In detail, halogenation means halogen (F, Cl, Br, I) substitution.

The compound of the present invention uses high mobility of thiophene (and selenophene) and thiophene (selenophene) as part of a π bridge or a π bridge, and selects appropriate D and A units so that it has low exciton binding energy and is effective. Reducing the highest occupied electron orbital level of the molecule allows high-efficiency materials to achieve high open circuit voltages.

Donor units that can be used in the present application include, but are not limited to:

Wherein R ₅ may be independently selected from C ₁ -C ₃₀ halo or non-halogenated alkyl, C ₁ -C ₃₀ halo or non-haloalkoxy, C ₁ -C ₃₀ halo or non-halogenated fluorenyl, C ₁ - C ₃₀ halo or non-halogenated cycloalkyl, C ₁ -C ₃₀ halo or non-halogenated carbonyl, C ₁ -C ₃₀ halo or non-halogenated ester and C ₁ -C ₃₀ halo or Any one of non-halogenated sulfone groups; X ₃ , X _{4 are} independently selected from sulfur, oxygen or selenium atoms.

Receptor units that can be used in the present application include, but are not limited to:

Wherein R ₆ and R ₇ may be independently selected from C ₁ -C ₃₀ halo or non-halogenated alkyl, C ₁ -C ₃₀ halo or non-haloalkoxy, C ₁ -C ₃₀ halo or non-halogenated fluorenyl, C _1- C ₃₀ halo or non-halogenated cycloalkyl, C ₁ -C ₃₀ halo or non-halogenated carbonyl, C ₁ -C ₃₀ halo or non-halogenated ester and C ₁ -C ₃₀ halo Or any of the non-halogenated sulfone groups.

In certain embodiments, the compound of Formula I is selected from one of the following structures:

Wherein R ₁ to R ₄ may be independently selected from H, C ₁ -C ₃₀ halo or non-halogenated alkyl, C ₁ -C ₃₀ halo or non-haloalkoxy, C ₁ -C ₃₀ halo or non-halogenated Mercapto group, C ₁ -C ₃₀ halo or non-halogenated cycloalkyl group, wherein R _m (m=1-4) may be the same or different. X ₁ -X ₄ may be independently selected from sulfur, oxygen, or a selenium atom, wherein X ₁ -X ₄ may be the same or different.

In certain embodiments, the compound of Formula I is selected from one of the following structures:

A further object of the present invention is to provide a process for the preparation of the compound of the present invention, which comprises preparing a compound by subjecting a bisaldehyde-based end group compound to a terminal acceptor unit by a knoevenage condensation reaction.

Preferably, the preparation method of the present invention comprises the following steps:

(1) under the protection of an inert gas, the π bridge monomer and the trimethyltin substituted donor unit, the catalyst is added to the organic solvent, and the reaction is heated to obtain a dialdehyde end group precursor;

(2) The above-mentioned bisaldehyde end group precursor, acceptor unit and catalyst are added to a solvent to react to obtain the target compound.

The reaction process is illustrated as follows:

Preferably, the inert gas in the step (1) is nitrogen or argon.

Preferably, the π bridge monomer is an alkylated thiophene and thiophene/selenophene, or a monoaldehyde terminal bromo compound of selenophene and thiophene/selenophene (ie, may be alkylated thiophene and thiophene) And thiophene and selenophene, and selenophene and thiophene, and selenophene and selenophene monothiol bromide), which may specifically be: 5-bromo-3,6-dihexylthiophene [3,2- b] thiophene-2-carbaldehyde (formula 1), 5-(5-bromo-6-hexyl[3,2-b]thiophen-2-yl)-4-hexylthiophene-2-carbaldehyde (formula 2), 5 -(5-bromo-6-hexyl[3,2-b]thiophen-2-yl)-4-hexylselenophene-2-carbaldehyde (Formula 3), 5-(5-bromo-6-hexyl[3, One of 2-b]selenophen-2-yl)-4-hexyllensene-2-carbaldehyde (Formula 4).

Preferably, the trimethyltin substituted donor unit may be one of the following:

Wherein R ₅ is H, C ₆ -C ₁₂ halo or non-halogenated alkyl, C ₆ -C ₁₂ halo or non-haloalkoxy, C ₆ -C ₁₂ halo or non-halogenated fluorenyl, C ₆ -C ₁₂ Halogenated or non-halogenated cycloalkyl, C ₆ -C ₁₂ halo or non-halogenated carbonyl, C ₆ -C ₁₂ halo or non-halogenated ester and C ₆ -C ₁₂ halo or non-halogenated Any of the sulfone groups.

Preferably, the catalyst is Pd(PPh ₃ ) ₄ .

Preferably, the solvent is toluene.

Preferably, the molar ratio of the π bridge monomer to the trimethyltin substituted donor unit is from 2 to 4:1.

Preferably, the molar amount of catalyst is from 5% to 10% of the π bridge monomer.

Preferably, the volume of solvent toluene in step (1) is from 10 to 100 mL/mmol relative to the amount of trimethyltin substituted donor unit.

Preferably, the temperature of the heating reaction is from 80 to 100 ° C, and the reaction time is from 12 to 48 h, preferably from 24 to 48 h.

Preferably, after the reaction of the step (1) is completed, the reaction solution is concentrated and purified by column.

Preferably, the concentration can be carried out by rotary steaming.

Preferably, the column purification uses a mixed solvent of dichloromethane and petroleum ether as a eluent.

Preferably, the molar ratio of the dialdehyde end group precursor to the acceptor unit in the step (2) is 1:1 to 15.

Preferably, the catalyst may be selected from one or a mixture of two or more of triethylamine, piperidine or pyridine.

Preferably, the catalyst is used in a molar amount of from 5 to 20% relative to the dialdehyde end group precursor.

Preferably, the temperature of the reaction is from 25 to 80 ° C and the reaction time is from 1 to 3 days.

Preferably, after the end of the reaction of the step (2), the reaction solution is concentrated, purified by column chromatography, and then recrystallized to obtain the target compound.

Preferably, the concentration is carried out by rotary steaming.

Preferably, the column purification uses a mixed solvent of chloroform and petroleum ether as a eluent.

Preferably, the recrystallization is carried out using a mixed solvent of chloroform and methanol.

A third object of the present invention is to provide a π bridge monomer having a structure as shown in the following formula II:

among them,

R ₁ -R ₄ may be independently selected from H, C ₁ -C ₃₀ halo or non-halogenated alkyl, C ₁ -C ₃₀ halo or non-haloalkoxy, C ₁ -C ₃₀ halo or non-halogen Mercapto, C ₁ -C ₃₀ halo or non-halogenated cycloalkyl, C ₁ -C ₃₀ halo or non-halogenated carbonyl, C ₁ -C ₃₀ halo or non-halogenated ester and C ₁ - Any one of a C ₃₀ halogenated or non-halogenated sulfone group. Wherein, R _{1 to} R ₄ may be the same or different. X ₁ and X ₂ may be independently selected from sulfur, oxygen or selenium atoms, wherein X ₁ and X ₂ may be the same or different.

The π bridge monomer of the present invention can be, for example:

A fourth object of the present invention is to provide a preparation method of the π bridge monomer of the present invention, which is mainly composed of a bromide coupling of a thiophene or a sulfenyl group substituted with a thiophene or a selenophene group and a monoaldehyde group. Prepared by rebromination.

Preferably, the method for preparing the π bridge monomer comprises the following steps:

(1) a borate ester of thiophene or a borate ester of selenophene under the protection of an inert gas, and a bromide of a monoaldehyde-substituted thiophene or selenophene, toluene, water, tetrahydrofuran, NaHCO ₃ , Pd ( PPh ₃ ) ₄ catalyst is added to the solvent of toluene to obtain a monoaldehyde-coupled compound;

(2) N-bromosuccinimide (NBS) is added to the compound of the monoaldehyde terminal group obtained in the step (1), and a mixture of acetic acid and chloroform is reacted to obtain the π bridge monomer.

For example, the π bridge monomer of the present invention can be synthesized by the following process:

Preferably, the inert gas in the step (1) is nitrogen or argon.

Preferably, the molar ratio of the boric acid ester of the thiophene or selenophene to the bromide of the monoaldehyde-substituted thiophene or selenophene is 1:1-2.

Preferably, the molar ratio of NaHCO ₃ to the bromide of the monoaldehyde-substituted thiophene or selenophene is from 3 to 10:1.

Preferably, the molar amount of Pd(PPh ₃ ) ₄ is from 2% to 10% of the monoaldehyde-substituted thiophene or the selenophene bromide.

Preferably, the toluene solvent is used in an amount of from 1 to 10 mL/mmol relative to the monoaldehyde-substituted thiophene or selenophene.

Preferably, the toluene:water:tetrahydrofuran volume ratio is 1:1:1-10.

Preferably, the temperature of the reaction is from 30 to 90 ° C and the reaction time is from 1 to 7 days.

Preferably, after the reaction of the step (1) is completed, the reaction solution is washed with water and concentrated, and then purified by column.

Preferably, the concentration can be carried out by rotary steaming.

Preferably, the column purification uses a mixed solvent of dichloromethane and petroleum ether as a eluent.

Preferably, the molar ratio of NBS to monoaldehyde-substituted thiophene or selenophene bromide in step (2) is from 1 to 1.2:1.

Preferably, the volume ratio of acetic acid to chloroform is from 0.1 to 3:1.

Preferably, the amount of chloroform relative to the monoaldehyde-substituted thiophene or selenophene is 5-50 mL/mmol.

Preferably, the temperature of the reaction is from -10 ° C to 25 ° C and the reaction time is from 4 to 48 hours.

Preferably, after the end of the reaction of the step (2), the reaction solution is extracted with water and purified by column to obtain the target compound.

Preferably, the extraction is carried out using chloroform.

Preferably, the column purification uses a mixed solvent of dichloromethane and petroleum ether as a eluent.

Receptor units can be synthesized using techniques known in the art. For example, it can be synthesized by the following process:

Where Y _n = H or F (n = 1-4), Y _n may be the same or different. Specific synthetic procedures can be found in the literature (J. Med. Chem., 16(12), 1334-1337).

A fifth object of the present invention is to provide the use of the compounds according to the invention in the field of photovoltaic devices, in particular as active layer donor/acceptor materials for solar cells.

According to the invention, on the basis of the π bridge, the organic photoelectric compound obtained by selecting appropriate D and A units has low exciton binding energy and can effectively reduce the highest occupied electron orbital level of the molecule, so that high-efficiency materials can obtain high open circuit voltage. . The compound based on the present invention is used as a donor material for an active layer of an organic solar cell, and its maximum open circuit voltage exceeds 1V. Among them, the fluorinated acceptor unit is used as the end group. Without any additives and solvents and thermal annealing treatment, the energy conversion efficiency of the forward structure of the battery exceeds 10%, and the energy conversion efficiency of the inverted device structure reaches 11.5%. The field of photovoltaic devices has important application value.

DRAWINGS

Figure 1 is a UV-visible absorption spectrum of M1 in a chloroform solution and a thin film state;

Figure 2 is a UV-visible absorption spectrum of M2 in a chloroform solution and a thin film state;

Figure 3 is a UV-visible absorption spectrum of M3 in a chloroform solution and a thin film state;

Figure 4 is a UV-visible absorption spectrum of M4 in a chloroform solution and a film state;

Figure 5 is a cyclic voltammetry curve measured by the electrochemical methods of M1 and M2;

Figure 6 is a cyclic voltammetry curve measured by the electrochemical methods of M3 and M4;

7 is a JV curve showing a soluble organic small molecule solar cell device having a forward device structure of ITO/PEDOT:PSS/M1:PC ₇₀ BM/Ca/Al;

8 is a JV curve showing a soluble organic small molecule solar cell device having a forward structure of ITO/PEDOT:PSS/M2:PC ₇₀ BM/Ca/Al;

9 is a JV curve showing a soluble organic small molecule solar cell device having a reverse device structure of ITO/ZnO/M3: PC ₇₀ BM/MoOx/Ag;

Figure 10 is a JV curve showing a soluble organic small molecule solar cell device having a reverse device structure of ITO/ZnO/M4: PC ₇₀ BM/MoOx/Ag.

detailed description

To facilitate an understanding of the invention, the invention is set forth below. It should be understood by those skilled in the art that the present invention is only to be construed as a

The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

Example 1: Synthesis of photoelectrochemical compounds M1, M2, M3 and M4.

An organic photoelectric compound for a solar cell, the chemical mechanism of which is represented by the formula (I), wherein more specific structures are as follows:

R₂＝R₄＝C₆H₁₃，R₃＝H后的具体结构如下所示：Where X ₁ =X ₂ =X ₃ =X ₄ =S,

The specific structure after R ₂ =R ₄ =C ₆ H ₁₃ and R ₃ =H is as follows:

Preparation and Synthesis of Photoelectric Compound M1

It mainly includes the following steps:

Synthesis of 1π bridge monomer 5-(5-bromo-6-hexyl[3,2-b]thiophen-2-yl)-4-hexylthiophene-2-carbaldehyde:

Synthesis of 2 intermediate dialdehyde end groups and target compound M1

3 specific steps for the synthesis of each compound:

Compound 3: Pb(PPh ₃ ) ₄ (5% mmol) was added to compound 1 (3 g, 8.57 mmol), compound 2 (2.5 g, 9.12 mmol), NaHCO ₃ (2.16 g, 25.7 mmol). After a mixture of tetrahydrofuran (48 ML), toluene (16 mL) and deionized water (16 mL), the mixture was bubbled for 20 minutes, and the temperature of the mixture was raised to 85 ° C for 48 hours. The reaction mixture was concentrated with EtOAc (EtOAc)EtOAc.

Compound 4: NBS (1.28 g, 7.2 mmol) was added portionwise to a mixture of compound 3 (3 g, 7.2 mmol) in chloroform (50 mL) and acetic acid (50 mL). After the addition was completed, the reaction solution was allowed to react to room temperature overnight. After completion of the reaction, the reaction solution was poured into 50 mL of chloroform, and the organic phase was washed three times with water, three times with saturated NaHCO ₃ and three times with water, and the organic phase washed with MgSO 4 . The reaction mixture was concentrated with EtOAc (EtOAc)EtOAc.

Compound 6: Pd(PPh ₃ ) _{4 was} added to a solution of compound 4 (496 mg, 1 mmol) and compound 5 (453 mg, 0.5 mmol) in dry toluene (40 mL). After bubbling for 20 minutes, the temperature of the mixture was raised to 100 ° C and reacted for 48 hours. After the reaction mixture was concentrated with EtOAc (EtOAc)EtOAc.

Target compound M1: Compound 6 (200 mg, 0.14 mmol), 1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione (218 mg, 1.4 mmol) and a catalyst under nitrogen atmosphere Piperidine (0.59 mg, 0.007 mmol) was added to 30 mL of dry chloroform and allowed to react at room temperature for 24 hours. The mixture was precipitated by adding methanol, and the solid portion was dissolved in chloroform, washed three times with water and dried over anhydrous magnesium sulfate. The organic phase was evaporated to remove the solvent, and petroleum ether:trichloromethane = 1:2 (volume ratio) was used as the eluting solvent, and the product was separated by silica gel chromatography. The product was recrystallized from EtOAc (EtOAc m.

Synthesis of Photoelectric Compound M2

The synthesis of the target compound M2 of the target compound M2 is similar to the synthesis of the compound M1. The catalyst used was also piperidine, and the eluent was a mixed solvent of petroleum ether: chloroform = 1:2, and the obtained product yield was 60%.

Synthesis of Photoelectric Compound M3

Compound 8: tetrabutyl acetoacetate (1.53 g) was added to 4-fluorophthalic anhydride (1.4 g), acetic anhydride (4.5 mL) and triethylamine (2.5 mL), and stirred at room temperature for 24 hours. Ice (3.3 g) and concentrated hydrochloric acid (2.91 mL) were added thereto, and after stirring for 10 minutes, 12.3 mL of 5 M hydrochloric acid was added. Add 50 mL of chloroform and wash twice with water. The organic phase was evaporated to dryness to give a solvent eluted with petroleum ether: methylene chloride = 2:1 (volume ratio) and eluted on silica gel column to yield 78% yield.

The synthesis of the target compound M3 target compound M3 is similar to the synthesis of compound M2. The catalyst used was triethylamine, and the eluent was a mixed solvent of petroleum ether: chloroform = 1:2, and the obtained product yield was 60%.

Synthesis of Photoelectric Compound M4

Compound 10: The synthesis of Compound 10 was similar to the synthesis of Compound 8, and the eluting solvent was petroleum ether: dichloromethane = 3:2 (volume ratio) to give a product yield of 70%.

The synthesis of the target compound M4 target compound M4 is similar to the synthesis of the target compound M3. Pick The catalyst used was triethylamine, and the eluent was a mixed solvent of petroleum ether: chloroform = 1:2 to give a product yield of 65%.

Example 2: The ultraviolet-visible absorption spectrum of the small molecule M1-M4 in a chloroform solution and a film state was measured.

A suitable amount of M1 or M2 is dissolved in chloroform to form a solution of a certain concentration, and a part of the solution is spin-coated on a quartz plate to form a film of a small molecule. The UV-visible absorption spectrum of the compound of M1-M4 measured in a chloroform solution and a film state is shown in Figs. It can be seen from the figure that M1-M4 has a broad absorption in the visible light region, and the film is red-shifted by about 80 nm with respect to the solution, indicating that the two have a good aggregation effect in the film.

Example 3: Measurement of cyclic voltammetry curves in the state of small molecule thin films

Figure 5 is a cyclic voltammogram based on M1 and M2 films, and Figure 6 is a cyclic voltammogram based on M3 and M4 films. The chloroform solution was applied to a platinum electrode, and Ag/Ag+ was used as a reference electrode, and after air-drying, it was placed in an acetonitrile solution of tetrabutylammonium hexafluorophosphate. The initial oxidation potential and the initial reduction potential obtained from the graph are then calculated by the formula E _HOMO =-e(Eonset ox+4.71)(eV), ELUMO=-e(Eonset red+4.71)(eV) The HOMO and LUMO energy levels of the compounds. The specific values are shown in Table 1. As can be seen from the table, all of the four materials have a lower maximum electron occupied orbit (HOMO), which provides a basis for obtaining a high open circuit for photovoltaic devices based on these two materials.

Example 4: Photovoltaic properties testing of M1 and M2 based on forward device structure

An organic solar cell device was prepared by solution spin coating using M1 or M2 as a donor and PC ₇₀ BM as a acceptor. The device structure is ITO/PEDOT: PSS/M1: PCBM/Ca/Al. The specific preparation method is as follows: M1 or M2 is blended with PC ₇₀ BM (donor: PC ₇₀ BM mass ratio: 1.5:1), and dissolved in chloroform to prepare a 10 mg/mL solution. An organic solar cell was fabricated on a transparent silver tin oxide (ITO) coated glass substrate. The transparent conductive glass with ITO was ultrasonically cleaned with deionized water, acetone and isopropanol for 15 minutes, then the surface of the substrate was treated with ozone, and PEDOT:PSS was spin-coated on ITO. The rotational speed of the spin coating was 2000- 6000 rpm, and dried at 150 ° C for 15 minutes to obtain an anode modified layer having a thickness of 30 nm. The solution of the small molecule and PC ₇₀ BM in chloroform was spin-coated uniformly on the anode modified layer at 600-4000 rpm in a glove box to obtain an active material layer having a thickness of 80-150 nm. Finally, Ca was evaporated onto the active material layer under a vacuum of 2×10 ^-6 Torr to form a cathode modified layer having a thickness of 20 nm; and Al was evaporated to a cathode modification under a vacuum of 2×10 ^-6 Torr. On the layer, a cathode having a thickness of 100 nm was formed, thereby obtaining a small molecule solar cell device. Using a 500W xenon lamp in combination with an AM1.5 filter as a white light source for simulating sunlight, adjusting the light intensity at the measurement site to 100 mW/cm ^-2 , using Kaithley for open circuit voltage and short circuit of the prepared polymer solar cell device Three parameters of current and fill factor were tested. Figures 7 and 8 are current-voltage graphs based on molecular M1 and M2 devices, respectively. Table 2 shows the specific device performance parameters for M1 and M2.

Example 5: Photovoltaic properties testing of M3 and M4 based on inverted device structures

An organic solar cell device was prepared by solution spin coating using M3 or M4 as a donor and PC ₇₀ BM as a acceptor. The device structure is ITO/ZnO/M3 or M4: PC ₇₀ BM/MoOx/Ag. The specific preparation method is as follows: M3 or M4 is blended with PC ₇₀ BM (donor: PC ₇₀ BM mass ratio: 1.3:1), and dissolved in chloroform to prepare a solution having a total concentration of 18.5 mg/mL. An organic solar cell was fabricated on a transparent silver tin oxide (ITO) coated glass substrate. The transparent conductive glass with ITO was ultrasonically cleaned with deionized water, acetone and isopropanol for 15 minutes, then the surface of the substrate was treated with ozone, and the ZnO precursor was spin-coated on the ITO. The rotational speed of the spin coating was 2000- 6000 rpm, and annealed at 200 ° C for 30 minutes to obtain a cathode modified layer having a thickness of 20 nm. The solution of the small molecule and PC ₇₀ BM in chloroform was spin-coated uniformly on the anode modified layer at 600-4000 rpm in a glove box to obtain an active material layer having a thickness of 80-150 nm. Finally, MoOx was evaporated onto the active material layer under vacuum of 2×10 ^-6 Torr to form an anode modified layer with a thickness of 5 nm; and Ag was vapor-deposited to the cathode under a vacuum of 2×10 ^-6 Torr. On the layer, an anode having a thickness of 100 nm was formed, thereby obtaining a small molecule solar cell device. Using a 500W xenon lamp in combination with an AM1.5 filter as a white light source for simulating sunlight, adjusting the light intensity at the measurement site to 100 mW/cm ^-2 , using Kaithley for open circuit voltage and short circuit of the prepared polymer solar cell device Three parameters of current and fill factor were tested. Figures 9 and 10 are current-voltage graphs based on molecular M3 and M4 devices, respectively. Table 3 shows the specific device performance parameters for M3 and M4.

Table 1 HOMO and LUMO levels tested by photovoltaic compounds M1-M4 using cyclic voltammetry.

Table 2 shows the solar device performance based on the forward device structure of the photovoltaic compounds M1 and M2.

Table 3 shows the performance of solar cell devices based on the reverse device structure of photovoltaic compounds M3 and M4.

In summary, the materials based on the present description all have a high open circuit voltage, and the photoelectric conversion efficiency can reach 11.5%, and no additive and heat/solvent annealing are required in the device preparation process, the device optimization is simple, and the cost is greatly saved. Moreover, the organic small molecule has a clear structure, high purity, good reproducibility of material and device performance, and therefore has the potential to be suitable for large-area preparation and application.

The Applicant declares that the present invention illustrates the detailed process equipment and process flow of the present invention by the above embodiments, but the present invention is not limited to the above detailed process equipment and process flow, that is, does not mean that the present invention must rely on the above detailed process equipment and The process can only be implemented. It should be apparent to those skilled in the art that any modifications of the present invention, equivalent substitution of the various materials of the products of the present invention, addition of auxiliary components, selection of specific means, and the like, are all within the scope of the present invention.

Claims (11)

An organic photoelectric compound for a solar cell, the structure of which is as shown in the following formula I:

among them, R ₁ -R _{4 are} independently selected from H, C ₁ -C ₃₀ halo or non-halogenated alkyl, C ₁ -C ₃₀ halo or non-haloalkoxy, C ₁ -C ₃₀ halo or non-halogenated Mercapto, C ₁ -C ₃₀ halo or non-halogenated cycloalkyl, C ₁ -C ₃₀ halo or non-halogenocarbonyl, C ₁ -C ₃₀ halo or non-haloester and C ₁ -C ₃₀ halo Any one of a substituted or non-halogenated sulfone group; X ₁ and X _{2 are} independently selected from sulfur, oxygen or selenium atoms; D is a donor unit and A is a receptor unit. The compound according to claim 1, wherein the donor unit is selected from one of the following structures:

Wherein R _{5 is} independently selected from C ₁ -C ₃₀ halo or non-haloalkyl, C ₁ -C ₃₀ halo or non-haloalkoxy, C ₁ -C ₃₀ halo or non-halogenated fluorenyl, C ₁ -C ₃₀ halo or non-halogenated cycloalkyl, C ₁ -C ₃₀ halo or non-halogenated carbonyl, C ₁ -C ₃₀ halo or non-halogenated ester and C ₁ -C ₃₀ halo or non Any one of halogenated sulfone groups; X ₃ and X _{4 are} independently selected from sulfur, oxygen or selenium atoms. The compound according to claim 1, wherein the receptor unit is selected from one of the following structures:

Wherein R ₆ and R _{7 are} independently selected from C ₁ -C ₃₀ halo or non-halogenated alkyl, C ₁ -C ₃₀ halo or non-haloalkoxy, C ₁ -C ₃₀ halo or non-halogenated fluorenyl, C ₁ -C ₃₀ halo or non-halogenated cycloalkyl, C ₁ -C ₃₀ halo or non-halogenated carbonyl, C ₁ -C ₃₀ halo or non-halogenated ester and C ₁ -C ₃₀ halo or Any of the non-halogenated sulfone groups. The compound according to any one of claims 1 to 3, wherein the compound of formula I is selected from one of the following structures:

Wherein R ₁ -R _{4 are} independently selected from H, C ₁ -C ₃₀ halo or non-haloalkyl, C ₁ -C ₃₀ halo or non-haloalkoxy, C ₁ -C ₃₀ halo or non-halogenated Mercapto, C ₁ -C ₃₀ halo or non-halogenated cycloalkyl, C ₁ -C ₃₀ halo or non-halogenated carbonyl, C ₁ -C ₃₀ halo or non-halogenated ester and C ₁ -C Any one of ₃₀ halogenated or non-halogenated sulfone groups; X ₁ -X _{4 are} independently selected from sulfur, oxygen, or selenium atoms. The compound according to any one of claims 1 to 4, wherein the compound of formula I is selected from one of the following structures:

A process for the preparation of a compound according to any one of claims 1 to 5, wherein the compound is prepared by subjecting a dialdehyde-based end group compound to a terminal acceptor unit by a Keneferner's condensation reaction; Preferably, the preparation method comprises the following steps: (1) under the protection of an inert gas, the π bridge monomer and the trimethyltin substituted donor unit, the catalyst is added to the organic solvent, and the reaction is heated to obtain a dialdehyde end group precursor; (2) The above-mentioned bisaldehyde end group precursor, acceptor unit and catalyst are added to a solvent to react to obtain the target compound. The preparation method according to claim 6, wherein the inert gas in the step (1) is nitrogen or argon; Preferably, the π bridge monomer is an alkylated thiophene and thiophene/selenophene, or a monoaldehyde terminal bromo compound of selenophene and thiophene/selenophene, preferably 5-bromo-3,6-di Hexylthieno[3,2-b]thiophene-2-carbaldehyde, 5-(5-bromo-6-hexyl[3,2-b]thiophen-2-yl)-4-hexylthiophene-2-carbaldehyde, 5 -(5-bromo-6-hexyl[3,2-b]thiophen-2-yl)-4-hexylselenophene-2-carbaldehyde, 5-(5-bromo-6-hexyl[3,2-b] One of selenophen-2-yl)-4-hexyllensene-2-carbaldehyde; Preferably, the trimethyltin substituted donor unit is one of the following:

Wherein R ₅ is H, C ₆ -C ₁₂ halo or non-halogenated alkyl, C ₆ -C ₁₂ halo or non-haloalkoxy, C ₆ -C ₁₂ halo or non-halogenated fluorenyl, C ₆ -C ₁₂ Halogenated or non-halogenated cycloalkyl, C ₆ -C ₁₂ halo or non-halogenated carbonyl, C ₆ -C ₁₂ halo or non-halogenated ester and C ₆ -C ₁₂ halo or non-halogenated Any of the sulfone groups; Preferably, the catalyst in the step (1) is Pd(PPh ₃ ) ₄ ; Preferably, the organic solvent in the step (1) is toluene; Preferably, the molar ratio of the π bridge monomer to the trimethyltin substituted donor unit is 2-4:1; Preferably, the molar amount of the catalyst in the step (1) is 5% to 10% of the π bridge monomer; Preferably, the amount of the organic solvent toluene in the step (1) is relative to the trimethyltin substituted donor unit. Is 10-100mL/mmol; Preferably, the temperature of the heating reaction in the step (1) is 80-100 ° C, the reaction time is 12-48 h, preferably 24-48 h; Preferably, after the reaction of the step (1) is completed, the reaction solution is concentrated and purified by column; Preferably, the column purification uses a mixed solvent of dichloromethane and petroleum ether as a eluent. The preparation method according to claim 6 or 7, wherein the molar ratio of the dialdehyde end group precursor to the acceptor unit in the step (2) is 1:1-15; Preferably, the catalyst in the step (2) is one or a mixture of two or more of triethylamine, piperidine or pyridine; Preferably, the molar amount of the catalyst in the step (2) is 5-20% of the dialdehyde end group precursor; Preferably, the temperature of the reaction in the step (2) is 25-80 ° C, and the reaction time is 1-3 days; Preferably, after the reaction of the step (2) is completed, the reaction solution is concentrated, purified by a column, and then recrystallized to obtain a target compound; Preferably, the column purification uses a mixed solvent of chloroform and petroleum ether as a eluent; Preferably, the recrystallization is carried out using a mixed solvent of chloroform and methanol. A π bridge monomer having a structure as shown in the following formula II:

among them, R ₁ -R _{4 are} independently selected from H, C ₁ -C ₃₀ halo or non-halogenated alkyl, C ₁ -C ₃₀ halo or non-haloalkoxy, C ₁ -C ₃₀ halo or non-halogenated Mercapto, C ₁ -C ₃₀ halo or non-halogenated cycloalkyl, C ₁ -C ₃₀ halo or non-halogenated carbonyl, C ₁ -C ₃₀ halo or non-halogenated ester and C ₁ -C Any one of ₃₀ halogenated or non-halogenated sulfone groups; X ₁ and X _{2 are} independently selected from sulfur, oxygen or selenium atoms; Preferably, the π bridge monomer is one of the following structures:

A method for preparing a π bridge monomer according to claim 9, which is prepared by bromide coupling and rebromination of a thiophene or a selenophene-substituted thiophene or a selenophene-substituted thiophene or selenophene; Preferably, the preparation method comprises the following steps: (1) a borate ester of thiophene or a borate ester of selenophene under the protection of an inert gas, and a bromide of a monoaldehyde-substituted thiophene or selenophene, toluene, water, tetrahydrofuran, NaHCO ₃ , Pd ( PPh ₃ ) ₄ catalyst is added to the solvent of toluene to obtain a monoaldehyde-coupled compound; (2) adding N-bromosuccinimide to the mixture of the monoaldehyde end group-coupled compound obtained in the step (1), acetic acid and chloroform to obtain the π bridge monomer; Preferably, the inert gas in the step (1) is nitrogen or helium; Preferably, the molar ratio of the boric acid ester of the thiophene or selenophene to the bromide of the monoaldehyde-substituted thiophene or selenophene is 1:1-2; Preferably, the molar ratio of NaHCO ₃ to the monoaldehyde-substituted thiophene or selenophene bromide is from 3 to 10:1; Preferably, the molar amount of Pd(PPh ₃ ) ₄ is from 2% to 10% of the monothiol substituted thiophene or the selenophene bromide; Preferably, the amount of toluene relative to the monoaldehyde-substituted thiophene or selenophene is 1-10 mL / mmol; Preferably, the volume ratio of toluene:water:tetrahydrofuran is 1:1:1-10; Preferably, the temperature of the reaction in the step (1) is 30-90 ° C, and the reaction time is 1-7 days; Preferably, after the reaction of the step (1) is completed, the reaction solution is washed with water and concentrated, and then purified by column; Preferably, the column purification uses a mixed solvent of dichloromethane and petroleum ether as a eluent; Preferably, the molar ratio of N-bromosuccinimide to monoaldehyde-substituted thiophene or selenophene bromide in step (2) is 1-1.2:1; Preferably, the volume ratio of acetic acid to chloroform is from 0.1 to 3:1; Preferably, the amount of chloroform relative to the monoaldehyde group of thiophene or selenophene is 5-50mL / mmol; Preferably, the temperature of the reaction in the step (2) is -10 ° C to 25 ° C, and the reaction time is 4 to 48 hours; Preferably, after the end of the reaction of the step (2), the reaction liquid is extracted with water and purified by column to obtain a target compound; Preferably, the extraction is carried out using chloroform; Preferably, the column purification uses a mixed solvent of dichloromethane and petroleum ether as a eluent. Use of a compound according to any one of claims 1 to 5 in the field of photovoltaic devices, in particular as an active layer donor/acceptor material for solar cells.

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