An organic small molecule hole transport material and its preparation method and application

Abstract

The present invention belongs to the field of solar cell technology, and particularly relates to an organic small molecule hole transport material, its preparation method, and application. A hole transport material having the structural formula: wherein X, Y, and Z are independently selected from any one of Se, S, and O elements, and X, Y, and Z are not all S elements; and R is selected from any one of a nitrogen-containing group, a sulfur-containing group, an oxygen-containing group, a halogen-substituted alkyl group, an alkyl group, a fluorine-containing group, a phenyl-containing group, a thiophene-containing group, a triphenylamine-containing group, a benzothiadiazole-containing group, a pyridine-containing group, a bithiphene-containing group, a diphenylamine-containing group, a selenophene-containing group, a pyridine-containing group, a triazine-containing group, a furan-containing group, and a carbazole-containing group. The perovskite solar cell of the present invention has excellent photoelectric conversion efficiency, and its preparation method is simple, easy to purify, low-cost, uses green solvents, and is friendly to the human body and the environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and in particular relates to an organic small molecule hole transport material and a preparation method and application thereof. Background Art

[0002] Perovskite solar cells generally consist of electrodes, an electron transport layer, a perovskite active layer, and a hole transport layer. The hole transport layer is a crucial component of perovskite solar cells, collecting and transporting holes injected from the perovskite active layer, effectively separating electrons and holes, and preventing the perovskite layer from direct contact with water and oxygen in the external environment. Therefore, the choice of hole transport material in the hole transport layer directly determines the photoelectric conversion efficiency and stability of perovskite solar cells, especially for flip-chip perovskite solar cells.

[0003] There are many materials for the hole transport layer, such as inorganic hole transport materials, organometallic hole transport materials, conjugated polymer hole transport materials, and organic small molecule hole transport materials. Organic small molecule materials have great potential in molecular synthesis and device manufacturing. The most famous of these is 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD). Spiro-OMeTAD has good solubility, film-forming properties, and relatively matched energy levels. The efficiency of perovskite solar cells using it as a hole transport material can exceed 25%, but its low glass transition temperature and hygroscopicity caused by dopants seriously affect the stability of the device. In addition, the synthesis process of Spiro-OMeTAD is complex and purification is difficult, resulting in its high cost.

[0004] To improve the efficiency and reduce the cost of perovskite solar cells, a series of new organic small molecule hole transport materials have been developed. Thiophene and its derivatives are representative of these small molecule materials. On the one hand, they possess suitable highest occupied molecular orbital (HOMO) energy levels; on the other hand, the sulfur-lead interaction induced by the sulfur atoms can effectively passivate the surface defects of the perovskite layer. Despite these advantages, when applied to perovskite solar cells, the performance of most materials does not meet the actual requirements. Moreover, the reagents used in the preparation of these materials are harmful to the environment and human health, which is not in line with the concept of green chemistry.

[0005] Therefore, there is an urgent need to provide a small molecule organic hole transport material that can be applied to perovskite solar cells to enable perovskite solar cells to have excellent photoelectric conversion efficiency. The preparation method is simple, easy to purify, low in cost, uses green solvents, and is friendly to the human body and the environment. Summary of the Invention

[0006] The present invention aims to solve one or more technical problems existing in the prior art and at least provide a beneficial alternative or create conditions. The present invention provides a small molecule organic hole transport material. Its application in perovskite solar cells can improve the perovskite solar cell's photoelectric conversion efficiency. The preparation method is simple, easy to purify, low-cost, and uses green solvents, making it friendly to both the human body and the environment.

[0007] The inventive concept of the present invention is as follows: The present invention utilizes a fused compound composed of three five-membered heterocyclic rings as the central core, and an organic small molecule hole transport layer material with R groups attached to both sides. This material has a suitable energy level, which enables the hole transport layer / perovskite interface in the perovskite solar cell to have a more appropriate energy level arrangement, lower non-radiative recombination losses at the hole transport layer / perovskite interface, and more efficient hole extraction. In addition, by increasing the contribution of sulfur, selenium, and oxygen atoms to molecular conjugation, the short-circuit current density and open-circuit voltage of the perovskite solar cell can be effectively improved, thereby optimizing the photoelectric conversion efficiency of the perovskite solar cell and making the perovskite solar cell have good photoelectric performance.

[0008] Therefore, a first aspect of the present invention provides an organic small molecule hole transport material.

[0009] Specifically, a small molecule organic hole transport material has a structural formula of.

[0010]

[0011] In the formula, X, Y, and Z are independently selected from any one of Se, S, and O elements, and X, Y, and Z are not S elements at the same time; R is selected from any one of a nitrogen-containing group, a sulfur-containing group, an oxygen-containing group, a halogen-substituted alkyl group, an alkyl group, a fluorine-containing group, a phenyl-containing group, a thiophene-containing group, a triphenylamine-containing group, a benzothiadiazole-containing group, a pyridine-containing group, a bithiphene-containing group, a diphenylamine-containing group, a selenophene-containing group, a pyridine-containing group, a triazine-containing group, a furan-containing group, and a carbazole-containing group.

[0012] Preferably, R is selected from any one of the following groups:

[0013]

[0014]

[0015]

[0016]

[0017] The dotted line represents the insertion position of the group.

[0018] Preferably, the organic small molecule hole transport material includes a compound having the following structure:

[0019]

[0020]

[0021] The second aspect of the present invention provides a method for preparing the organic small molecule hole transport material described in the first aspect of the present invention.

[0022] Specifically, a method for preparing an organic small molecule hole transport material comprises the following steps:

[0023] Mixing a1 and a2 in a solvent and reacting them to prepare the organic small molecule hole transport material;

[0024] The structural formula of a1 is as follows:

[0025]

[0026] The structural formula of a2 is as follows:

[0027]

[0028] Preferably, the molar ratio of a1 to a2 is (2.2-2.8):1.

[0029] Further preferably, the molar ratio of a1 to a2 is (2.4-2.6):1.

[0030] More preferably, the molar ratio of a1 to a2 is 2.5:1.

[0031] Preferably, the reaction temperature is 80-100° C., and the reaction time is 22-26 h.

[0032] More preferably, the reaction temperature is 85-95° C., and the reaction time is 23-25 ​​h.

[0033] More preferably, the reaction temperature is 90° C. and the reaction time is 24 h.

[0034] Preferably, the reaction is carried out in a gas atmosphere, and the gas includes argon.

[0035] Preferably, the solvent is tetrahydrofuran; the reaction is carried out in a catalytic system comprising tetrakistriphenylphosphine palladium and K2CO3 aqueous solution.

[0036] Specifically, the tetrahydrofuran solvent used in the present invention is a green solvent that does not cause harm to the environment and human body.

[0037] Preferably, after the reaction, the organic small molecule hole transport material is obtained by extraction, drying and purification.

[0038] Preferably, after the reaction, the mixture is cooled to room temperature, and then extracted, dried, and purified to obtain the organic small molecule hole transport material.

[0039] Preferably, the extraction is carried out using an extractant selected from at least one of dichloromethane, n-hexane, and chloroform; the drying is carried out using a desiccant selected from at least one of anhydrous Na2SO4, anhydrous MgSO4, and anhydrous CaCl2; the purification is carried out using an eluent selected from at least one of a mixture of petroleum ether and ethyl acetate, a mixture of petroleum ether and dichloromethane, and a mixture of petroleum ether and chloroform.

[0040] Preferably, the drying is to dry the collected organic layer using anhydrous Na2SO4.

[0041] Preferably, the purification is performed by column chromatography on silica gel using an eluent to obtain a pure product of the organic small molecule hole transport material.

[0042] Preferably, the silica gel has a mesh size of 270-440; more preferably, the silica gel has a mesh size of 300-400.

[0043] Preferably, the volume ratio of petroleum ether to ethyl acetate is (4.5-5.5):1.

[0044] Further preferably, the volume ratio of petroleum ether to ethyl acetate is 5:1.

[0045] A third aspect of the present invention provides a hole transport layer.

[0046] Specifically, the hole transport layer includes the organic small molecule hole transport material described in the first aspect of the present invention.

[0047] A fourth aspect of the present invention provides a perovskite solar cell.

[0048] Specifically, the perovskite solar cell includes the organic small molecule hole transport material described in the first aspect of the present invention or the hole transport layer described in the third aspect of the present invention.

[0049] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0050] (1) The present invention uses a condensed compound composed of three five-membered heterocyclic rings as the central core and a small molecule organic hole transport layer material with R groups connected on both sides. The small molecule organic hole transport layer material has a suitable energy level, so that the hole transport layer / perovskite interface in the perovskite solar cell has a more suitable energy level arrangement, the non-radiative recombination loss at the hole transport layer / perovskite interface is lower, and the hole extraction efficiency is high, so that the perovskite solar cell has good photoelectric performance.

[0051] (2) The hole transport material of the present invention contains sulfur, selenium, and oxygen atoms, which contribute to the molecular conjugation and can effectively improve the short-circuit current density and open-circuit voltage of the perovskite solar cell, thereby optimizing the photoelectric conversion efficiency of the perovskite solar cell and making the perovskite solar cell have good photoelectric performance.

[0052] (3) The perovskite solar cell of the present invention achieves high efficiency while the Me-THF reagent used in the preparation of its hole transport material is an environmentally friendly reagent, which is green and environmentally friendly to the human body and the environment, and is conducive to the industrial application of perovskite solar cells.

[0053] (4) The present invention specifically studies the effect of the hole transport layer materials of organic small molecules based on regioisomerized fused pentacyclic compounds on device performance, which has certain guiding significance for the further development of hole transport layer materials of organic small molecules that can finely control energy levels, band gaps, absorption, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Schematic diagram of the preparation process of the hole transport material of Example 1 of the present invention;

[0055] Figure 2 This is a hydrogen nuclear magnetic resonance spectrum of the hole transport material of Example 1 of the present invention;

[0056] Figure 3 This is the carbon nuclear magnetic resonance spectrum of the hole transport material of Example 1 of the present invention;

[0057] Figure 4 This is a current-voltage curve of the perovskite solar cell of Application Example 1 of the present invention;

[0058] Figure 5 This is a schematic diagram of the preparation process of the hole transport material according to Example 2 of the present invention;

[0059] Figure 6 This is a hydrogen nuclear magnetic resonance spectrum of the hole transport material of Example 2 of the present invention;

[0060] Figure 7 This is a current-voltage curve of the perovskite solar cell of Application Example 2 of the present invention. DETAILED DESCRIPTION

[0061] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0062] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0063] Example 1: Preparation of compound (1)

[0064]

[0065] A method for preparing a hole transport material of organic small molecules, see attached Figure 1 The hole transport material is prepared according to the synthesis route shown in the figure, which specifically includes the following steps:

[0066] Under argon atmosphere, a1 4-methoxy-N-(4-methoxyphenyl)-N-(4,4,5,5-tetramethyl-1,3,2-dioxaborol-2-yl)-p-phenyl)aniline (304.52 mg, 0.706 mmol), a2 2,6-Dibromodiselenolo[3,2-b:2',3'-d]thiophene (126.31 mg, 0.282 mmol) was mixed with tetrakistriphenylphosphine palladium (Pd(PPh3)4) (26.11 mg, 0.023 mmol), K2CO3 (2M aqueous solution, 2.5 mL) and THF (tetrahydrofuran) (5 mL), added to a 10 mL Schlenk flask, and reacted at 90°C for 24 h; after cooling to room temperature, the reaction mixture was extracted with CH2Cl2, the collected organic layer was dried over anhydrous Na2SO4, and then purified by column chromatography on 350 mesh silica gel with an eluent of petroleum ether:ethyl acetate in a volume ratio of 5:1 to obtain an organic small molecule hole transport material of formula (1).

[0067] The hydrogen nuclear magnetic resonance spectrum of the organic small molecule hole transport material prepared above is as follows: Figure 2 As shown. Among them, Figure 2 (a) is an enlarged view of the boxed area in Figure (2).

[0068] The characterization results of H NMR spectrum are: 1 H NMR (500MHz, CDCl3) δ (ppm): 7.50 (s, 1H), 7.37 (d, 2H), 7.10 (d, 4H), 6.92 (d, 2H), 6.86 (d, 4H), 3.81 (s, 3H).

[0069] The carbon nuclear magnetic resonance spectrum of the organic small molecule hole transport material prepared above is as follows: Figure 3 shown.

[0070] The characterization results of carbon nuclear magnetic resonance spectroscopy are: 13 C NMR (126MHz, CDCl3) δ (ppm): 156.14, 149.67, 148.60, 142.22, 140.47, 131.93, 128.31, 126.82, 126.58, 120.28, 116.78, 114.79, 55.52.

[0071] Application Example 1

[0072] The small molecule organic hole transport material prepared in Example 1 was dissolved in chlorobenzene (CB) and spin-coated on an indium tin oxide semiconductor transparent conductive film (ITO) at 3000 r / min for 30 s. A perovskite material composed of methylamine lead iodide perovskite (MAPbI3) was spin-coated on the small molecule organic hole transport material at 3000 r / min for 30 s. A derivative of fullerene C60, [6,6]-phenyl-C61-butyric acid methyl ester (PC) was spin-coated on the perovskite material at 3000 r / min for 30 s. 61 BM), PC 61 BM was used as the electron transport layer, and finally a 110nm silver electrode was evaporated to prepare a perovskite solar cell.

[0073] Performance Testing

[0074] Photoelectric performance test

[0075] The photoelectric performance test of the perovskite solar cell corresponding to Example 1 is carried out. The test method of the photoelectric performance test is as follows: the cell device is tested under AM1.5G light intensity, and the model of the solar simulator used is SS-F5-3A, so that the photocurrent-voltage characteristic curve (JV curve) can be obtained. The short-circuit current density (J SC ), open circuit voltage (V OC ) and fill factor (FF).

[0076] The current-voltage curve of the perovskite solar cell in Application Example 1 is as follows: Figure 4 As shown, the horizontal axis Voltage represents voltage, V represents the unit is volt, and the vertical axis Current Density represents the current density, mA / cm 2 Indicates milliamperes per square centimeter.

[0077] Depend on Figure 4 It can be concluded that the hole transport material of the organic small molecule prepared in Example 1 has a J of 0.SC , V OC , photoelectric conversion efficiency (PCE) and FF, the specific test results are shown in Table 1.

[0078] Table 1: Photovoltaic performance of perovskite solar cells in application example 1

[0079] Material <![CDATA[V OC (V)]]> <![CDATA[J SC (mA / cm 2 )]]> FF(%) PCE (%) Perovskite solar cells 1.064 23.541 72.958 18.157

[0080] As shown in Table 1, the perovskite solar cell prepared using the small molecule organic hole transport material of Example 1 exhibited excellent photoelectric conversion efficiency, achieving a high photoelectric conversion efficiency of 18.157%, demonstrating excellent photoelectric performance. This is because the HOMO energy level of the hole transport material of Example 1 more closely matches that of the perovskite film, resulting in lower non-radiative recombination losses at the hole transport layer / interface and more efficient hole extraction. Furthermore, this photoelectric conversion efficiency is one of the highest values ​​reported for perovskite solar cells with a hole transport layer processable with the green solvent Me-THF.

[0081] Example 2: Preparation of compound (2)

[0082]

[0083] A method for preparing a hole transport material of organic small molecules, see attached Figure 5 The hole transport material is prepared according to the synthesis route shown in the figure, which specifically includes the following steps:

[0084] Under argon atmosphere, a1 4-methoxy-N-(4-methoxyphenyl)-N-(4,4,5,5-tetramethyl-1,3,2-dioxaborol-2-yl)-p-phenyl)aniline (304.52 mg, 0.706 mmol), a2 2,6-Dibromodiselenophene [3,2-b: 2', 3'-d] selenophene (139.31 mg, 0.282 mmol) was mixed with tetrakistriphenylphosphine palladium (Pd(PPh3)4) (26.11 mg, 0.023 mmol), K2CO3 (2M aqueous solution, 2.5 mL) and THF (tetrahydrofuran) (5 mL), added to a 10 mL Schlenk flask, and reacted at 90°C for 24 h; after cooling to room temperature, the reaction mixture was extracted with CH2Cl2, the collected organic layer was dried over anhydrous Na2SO4, and then purified by column chromatography on 350 mesh silica gel with an eluent of petroleum ether: ethyl acetate in a volume ratio of 5:1 to obtain an organic small molecule hole transport material of formula (2).

[0085] The hydrogen nuclear magnetic resonance spectrum of the organic small molecule hole transport material prepared above is as follows: Figure 6 shown.

[0086] The characterization results of H NMR spectrum are: 1 H NMR (500MHz, CDCl3) δ (ppm): 7.50 (s, 1H), 7.37 (d, 2H), 7.10 (d, 4H), 6.92 (d, 2H), 6.86 (d, 4H), 3.81 (s, 3H).

[0087] Application Example 2

[0088] The small molecule organic hole transport material prepared in Example 2 was dissolved in chlorobenzene (CB) and spin-coated on an indium tin oxide semiconductor transparent conductive film (ITO) at 3000 r / min for 30 s. A perovskite material composed of methylamine lead iodide perovskite (MAPbI3) was spin-coated on the small molecule organic hole transport material at 3000 r / min for 30 s. A derivative of fullerene C60, [6,6]-phenyl-C61-butyric acid methyl ester (PC) was spin-coated on the perovskite material at 3000 r / min for 30 s. 61 BM), PC 61 BM was used as the electron transport layer, and finally a 110nm silver electrode was evaporated to prepare a perovskite solar cell.

[0089] Performance Testing

[0090] Photoelectric performance test

[0091] The photoelectric performance test of the perovskite solar cell corresponding to Example 2 is carried out. The test method of the photoelectric performance test is as follows: the cell device is tested under AM1.5G light intensity, and the model of the solar simulator used is SS-F5-3A, so that the photocurrent-voltage characteristic curve (JV curve) can be obtained. The JV curve can directly obtain the J of the cell. SC 、V OC and FF.

[0092] The current-voltage curve of the perovskite solar cell in Application Example 2 is as follows: Figure 7 As shown, the horizontal axis Voltage represents voltage, V represents the unit is volt, and the vertical axis Current Density represents the current density, mA / cm 2 Indicates milliamperes per square centimeter.

[0093] Depend on Figure 7 It can be concluded that the hole transport material of the organic small molecule prepared in Example 2 has a J of 0. SC , V OC , PCE and FF, the specific test results are shown in Table 2.

[0094] Table 2: Photovoltaic performance of perovskite solar cells in application example 2

[0095] Material <![CDATA[V OC (V)]]> <![CDATA[J SC (mA / cm 2 )]]> FF(%) PCE (%) Perovskite solar cells 1.069 24.303 66.499 17.163

[0096] As shown in Table 2, the perovskite solar cell prepared using the small molecule organic hole transport material of Example 2 exhibits excellent photoelectric conversion efficiency, achieving a high photoelectric conversion efficiency of 17.163%, demonstrating excellent photoelectric performance. This is because the HOMO energy level of the hole transport material of Example 2 is more closely matched to the perovskite film, resulting in lower non-radiative recombination losses at the hole transport layer / interface and more efficient hole extraction. Furthermore, this photoelectric conversion efficiency is one of the highest values ​​reported for perovskite solar cells with a hole transport layer processable with the green solvent Me-THF.

[0097] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A hole transport material, characterized in that The hole transport material includes a compound with the following structure:

2. The method for preparing the hole transport material according to claim 1, wherein: The following steps are involved: Mixing a1 and a2 in a solvent and reacting them to prepare the hole transport material; The structural formula of a1 is: The R is The structural formula of a2 is: The solvent is tetrahydrofuran; the reaction is carried out in a catalytic system, which comprises tetrakistriphenylphosphine palladium and K2CO3 aqueous solution.

3. The preparation method according to claim 2, characterized in that The molar ratio of a1 to a2 is 2.2-2.8:

1.

4. The preparation method according to claim 2, characterized in that The reaction temperature is 80-100° C., and the reaction time is 22-26 h.

5. The preparation method according to claim 2, characterized in that After the reaction, the hole transport material is obtained by extraction, drying and purification.

6. A hole transport layer, characterized in that: The hole transport material according to claim 1 is included.

7. A perovskite solar cell, characterized in that: The method comprises the hole transport material according to claim 1 or the hole transport layer according to claim 6.

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