Synthetic method and application of self-assembled monomolecular layer hole transport material based on carbazole derivative

Abstract

The invention designs and synthesizes a self-assembled monomolecular layer hole transport material based on a carbazole derivative, and an application of the self-assembled monomolecular layer hole transport material in a trans-broadband gap perovskite solar cell. Halogen is introduced into a parent nucleus molecule, the HOMO energy level of the molecule can be reduced, and matching with the energy level of perovskite is facilitated. A carbazole derivative with a conjugated large plane is used as a parent nucleus, so that molecules are endowed with good hole transport performance. Through the anchoring effect of the upper and lower double anchoring groups, the energy loss at the interface is reduced, the complete coverage and bonding of the hole transport material on the surface of the substrate can be improved, and the cell efficiency is improved; alkyl chains with different chain lengths are used as linking groups, so that the material is endowed with enough rotational degree of freedom. The self-assembled monomolecular layer hole transport material based on the carbazole derivative is synthesized at low cost by adopting simplified synthesis steps, and the prepared material can realize dual functions of hole transport and perovskite interface passivation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of new materials for solar cells, and more particularly relates to a synthesis method of a self-assembled monolayer hole transport material and application thereof. BACKGROUND

[0002] Perovskite solar cells have been rapidly developed in the photovoltaic field since they were first reported in 2009, due to their solution processability, tunable band gap, high efficiency, and potential low cost. They are considered as the next generation of commercial solar cells with great potential, comparable to silicon-based solar cells.

[0003] In the structure system of perovskite solar cells, the transverse structure (p-i-n) has attracted widespread attention in academic research and industrialization process due to its simple processing technology, easy realization of relatively low temperature preparation, and better stability. In recent years, through various optimization strategies, the efficiency of transverse perovskite solar cells has successfully broken through 27%. In the structure composition of transverse perovskite solar cells, the hole transport layer plays a crucial role, and its performance directly affects the overall performance of the cell, including perovskite crystallization, interface carrier extraction rate, charge transport effect, and recombination.

[0004] Currently, the traditional hole transport layer materials used in transverse perovskite solar cells, such as poly(triarylamine) (PTAA), nickel oxide (NiOx), and poly(3,4-ethylenedioxythiophene): poly(styrene sulfonic acid) (PEDOT:PSS), all have certain limitations. PTAA has hydrophobicity, which can lead to poor wettability at the interface between the perovskite layer and the hole transport layer, making it difficult to prepare the perovskite active layer; NiOx is prone to redox reaction with the perovskite surface, thereby reducing the stability of the cell; and PEDOT:PSS is acidic, which can not only corrode the electrode but also easily absorb moisture, and its HOMO energy level does not match well with the perovskite layer, resulting in a low open-circuit voltage (Voc) of the device. These problems seriously restrict the improvement of the efficiency and stability of transverse perovskite solar cells, hindering their large-scale commercial application.

[0005] In addition, existing self-assembled monolayers (SAMs) as hole transport layer materials are mainly adsorbed on the surface of transparent conductive layers (TCO) through chemical means. When the device is exposed to a high temperature environment or undergoes thermal cycle impact, the molecular layer is prone to detachment or aggregation, which can cause interface contact deterioration, hinder the transport of carriers (holes), and ultimately lead to a significant decrease in device performance and stability.

[0006] Due to the problems faced by the above-mentioned traditional hole transport layer materials in the application of trans-formamium solar cells, it is urgent to develop new, efficient and stable hole transport layer materials. This is of great practical significance for further improving the performance of trans-formamium solar cells and promoting their industrialization process. SUMMARY

[0007] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a self-assembled monolayer hole transport material with high solubility, good hole transport performance, strong interface passivation ability and suitability for large-scale application. The synthesized molecule is used to prepare a perovskite solar cell.

[0008] 1. A self-assembled monolayer hole transport material based on a carbazole derivative, characterized in that:

[0009] has the following structural formula:

[0010]

[0011] in the formula, R l = -C2H4-, -C3H6-, -C4H8-, -C6H 12 -;

[0012] R2 = F, Cl, Br.l.

[0013] 2. The self-assembled monolayer hole transport material of claim 1, wherein the self-assembled monolayer hole transport material based on a carbazole derivative is applied to a trans-wide band gap perovskite solar cell.

[0014] 3. The use of the self-assembled monolayer hole transport material of claim 1, wherein the structure of the perovskite solar cell is ITO / HTI / perovskite / C 60 / BCP / Ag from bottom to top, and the HTL is a self-assembled monolayer hole transport material based on a carbazole derivative.

[0015] Advantages:

[0016] (1) The hole transport material described in the present application introduces halogen into the parent nucleus. Due to the electron-withdrawing property of halogen, the solubility of the compound can be improved, which is beneficial to its use as a self-assembled monolayer hole transport material. It can also lower the HOMO energy level of the molecule, which is beneficial to its better matching with the perovskite energy level.

[0017] (2) The hole transport material described in the present application uses a carbazole derivative with a rigid conjugated large plane as the parent nucleus, which endows the molecule with good hole transport performance.

[0018] (3) The hole transport material described in the application, through the conjugate extension of indolocarbazole and biscalbazole, realizes the reduction of energy loss at the interface by means of its interface passivation characteristics, and improves the battery efficiency.

[0019] (4) The hole transport material described in the application can realize more than 20% wide band gap perovskite solar cells. It is illustrated that the hole transport material described in the application is a kind of material with excellent performance. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 NMR hydrogen spectrum of the 2 material prepared in the application;

[0021] Figure 2 NMR carbon spectrum of the 2 material prepared in the application;

[0022] Figure 3 NMR hydrogen spectrum of the 3 material prepared in the application;

[0023] Figure 4 NMR carbon spectrum of the 3 material prepared in the application;

[0024] Figure 5 NMR hydrogen spectrum of the 9, 9-DCz material prepared in the application;

[0025] Figure 6 NMR carbon spectrum of the 9, 9-DCz material prepared in the application;

[0026] Figure 7 High resolution mass spectrum of the 9, 9-DCz material prepared in the application;

[0027] Figure 8 NMR hydrogen spectrum of the 5 material prepared in the application;

[0028] Figure 9 NMR carbon spectrum of the 5 material prepared in the application;

[0029] Figure 10 NMR hydrogen spectrum of the 6 material prepared in the application;

[0030] Figure 11 NMR carbon spectrum of the 6 material prepared in the application;

[0031] Figure 12 NMR hydrogen spectrum of the 5, 11-IDCz material prepared in the application;

[0032] Figure 13 NMR carbon spectrum of the 5, 11-IDCz material prepared in the application;

[0033] Figure 14 High resolution mass spectrum of the 5, 11-IDCz material prepared in the application;

[0034] Figure 15 NMR of hydrogen of 8 material prepared in the present application;

[0035] Figure 16 NMR of carbon of 8 material prepared in the present application;

[0036] Figure 17 NMR of hydrogen of 9 material prepared in the present application;

[0037] Figure 18 NMR of carbon of 9 material prepared in the present application;

[0038] Figure 19 NMR of hydrogen of 5,7-IDCz material prepared in the present application;

[0039] Figure 20 NMR of carbon of 5,7-IDCz material prepared in the present application;

[0040] Figure 21 High resolution mass spectrum of 5,7-IDCz material prepared in the present application;

[0041] Figure 22 J-V curve of 9,9-DCz prepared in the present application as a hole transport material for perovskite solar cell;

[0042] Figure 23 J-V curve of 5,11-IDCz prepared in the present application as a hole transport material for perovskite solar cell;

[0043] Figure 24 J-V curve of 5,7-IDCz prepared in the present application as a hole transport material for perovskite solar cell;

[0044] Figure 25 Structure schematic diagram of perovskite solar cell prepared in the present application. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0046] Example 1: Synthesis of (6,6'-dibromo-9H,9'H-[3,3'-bicarbazole]-9,9'-diylbis(butan-4,1-diyl))bisphosphonic acid (9,9-DCz) self-assembled hole transport material:

[0047] The synthesis route is as follows:

[0048]

[0049] Step one:

[0050] A solution of 9H, 9'H-3,3'-bicarbazole (1) (1 g, 3.0 mmol) in DMF (5 mL) was taken in a 250 mL round bottom flask. Subsequently, a solution of N-bromosuccinimide (NBS, 1.3 g, 7.5 mmol) in DMF (5 mL) was slowly added to the reaction vessel under ice bath conditions. The reaction was carried out at room temperature for 5.5 h. After completion of the reaction, the reaction solution was slowly poured into 200 ml of water. It was then washed with brine and ethyl acetate three times. The organic phase was dried over Na2S04and concentrated under reduced pressure to get the crude product. Subsequently, it was purified by column chromatography on silica gel using petroleum ether: ethyl acetate (8:1 v / v) to get compound 6, 6'-dibromo-9H, 9'H-3,3'-bicarbazole (2) as a white solid (1.21 g, 82.3%). Its NMR characterization data are 1 H NMR (400 MHz, DMSO-d6) δ 11.43 (s, 2H), 8.58 (d, J = 1.5 Hz, 2H), 8.44 (d, J = 1.5 Hz, 2H), 7.83 (dt, J = 6.4, 0.9 Hz, 2H), 7.57 (d, J = 6.3 Hz, 2H), 7.52 - 7.41 (m, 4H). 13 C NMR (101 MHz, DMSO-d6) δ 139.08, 138.80, 132.24, 127.84, 125.49, 124.60, 122.85, 122.12, 118.48, 112.93, 111.40, 110.47.

[0051] Step two:

[0052] A solution of compound 2 (1 g, 2.04 mmol), 1,4-dibromobutane (8.8 g, 40.8 mmol), tetrabutylammonium iodide (0.15 g, 0.41 mmol) was taken in a 250 mL round bottom flask, all dissolved in 15 ml of toluene, followed by the addition of 20 ml of 50% KOH solution. The mixture was degassed three times by a pump and then kept under argon atmosphere. The mixture was heated to 70 °C for 24 h. After completion of the reaction, water was added and extracted with ethyl acetate three times. The organic phase was dried over Na2S04and concentrated under reduced pressure to get the crude product. It was purified by column chromatography on silica gel using petroleum ether: ethyl acetate (20:1 v / v) to get compound 6, 6'-dibromo-9,9'-bis(4-bromobutyl)-9H,9'H-3,3'-bicarbazole (3) as a white solid (1.11 g, 71.6%). Its NMR characterization data are 1H NMR (400 MHz, DMSO-d6) δ 8.64 (d, J = 1.8 Hz, 2H), 8.48 (t, J = 1.8 Hz, 2H), 7.92 (dt, J = 6.5, 1.7 Hz, 2H), 7.73 (dd, J = 6.5, 1.8 Hz, 2H), 7.68 - 7.51 (m, 4H), 4.50 - 4.43 (m, 4H), 3.53 (td, J = 4.8, 1.8 Hz, 4H), 1.99 - 1.78 (m, 8H). 13 C NMR (101 MHz, DMSO-d6) δ 140.01, 139.70, 132.90, 128.65, 126.24, 124.85, 123.64, 122.35, 119.34, 112.05, 111.48, 110.52, 42.18, 35.26, 30.32, 27.82.

[0053] Step three:

[0054] In a 100 mL round bottom flask was added compound 3 (0.5 g, 0.66 mmol) and triethyl phosphite (4.5 mL) and heated to 160 °C and stirred under a nitrogen atmosphere for 24 h. The excess triethyl phosphite was removed by distillation under reduced pressure to give a yellow oil which was used without further purification. The yellow oil was dissolved in 20 mL of anhydrous 1,4-dioxane and trimethylsilyl bromide (2.02 g, 13.2 mmol) was added dropwise at room temperature and stirred under a nitrogen atmosphere for 24 h. Then 5 mL of methanol was added and stirring was continued for 3 h. The liquid was removed by concentration under reduced pressure. The crude product was dissolved in methanol and then added dropwise to deionized water until the mixture became opaque. The final filtration gave a white solid (6,6'-dibromo-9H,9'H-[3,3'-bicarbazole]-9,9'-diyl bis(butan-4,1-diyl))bisphosphonic acid (9,9-DCz) (0.26 g, 63 %). Its NMR characterization data are 1 H NMR (400 MHz, DMSO-d6) δ 8.63 (s, 2H), 8.48 (d, J = 7.7 Hz, 2H), 7.91 (d, J = 6.4 Hz, 2H), 7.72 (d, J = 6.3 Hz, 2H), 7.66 - 7.50 (m, 4H), 4.42 (s, 4H), 1.84 (s, 4H), 1.20 (d, J = 7.1 Hz, 4H), 1.10 (t, J = 5.2 Hz, 4H). 13C NMR (101 MHz, DMSO-d6) δ 139.97, 139.68, 132.79, 128.58, 126.15, 124.78, 123.54, 122.28, 119.23, 112.09, 111.34, 110.51, 42.84, 30.22, 20.89, 16.99. MS: m / z (%) [M-] calcd for C 32 H 31 Br2N2O6P2: 761.06; found: 761.00.

[0055] Example 2: Synthesis of ((2,8-dibromoindolo[3,2-b]carbazole-5,11-diylbis(butan-4,1- diyl))bisphosphonic acid (5,11-IDCz) self-assembled hole transport material

[0056] The synthetic route is as follows:

[0057]

[0058] Step one:

[0059] The detailed synthesis procedure of 2,8-dibromo-5,11-dihydroindolo[3,2-b]carbazole (compound 5) was consistent with compound 2, and brown solid was finally obtained. Its NMR characterization data were 1 H NMR (400 MHz, DMSO-d6) δ 11.75 (s, 1H), 11.72 (s, 1H), 8.78 (q, J = 1.7 Hz, 2H), 7.71-7.49 (m, 6H). 13 C NMR (101 MHz, DMSO-d6) δ 142.05, 135.40, 127.64, 124.49, 124.28, 122.59, 114.02, 112.12, 96.35.

[0060] Step two:

[0061] The detailed synthesis procedure of 2,8-dibromo-5,11-dihydroindolo[3,2-b]carbazole (compound 5) was consistent with compound 2, and brown solid was finally obtained. Its NMR characterization data were 1H NMR (400 MHz, DMSO-d6) δ 9.10 (dd, J = 4.9, 3.2 Hz, 1H), 9.01 (d, J = 8.2 Hz, 1H), 7.79 - 7.75 (m, 2H), 7.75 - 7.71 (m, 2H), 7.62 (t, J = 7.7 Hz, 1H), 7.33 (t, J = 7.5 Hz, 1H), 4.88 (s, 4H), 3.59 - 3.54 (m, 4H), 1.90 (s, 8H). 13 C NMR (101 MHz, DMSO-d6) δ 142.21, 133.37, 128.09, 124.02, 123.73, 122.24, 115.46, 112.42, 97.31, 44.03, 35.14, 29.95, 29.08.

[0062] Step three:

[0063] ((2,8-dibromoindolo[3,2-b]carbazole-5,11-diylbis(butan-4,1-diyl))bisphosphonic acid (5,11-IDCz) was synthesized according to the procedure of compound 9,9-DCz. The yellow solid was obtained and characterized by NMR 1 H NMR (400 MHz, DMSO-d6) δ 9.06 (d, J = 1.6 Hz, 2H), 8.12 (s, 2H), 7.73 (d, J = 8 Hz, 4H), 4.47 (s, 4H), 1.85 (d, J = 3.6 Hz 4H), 1.13 (m, 8H). 13 C NMR (101 MHz, DMSO-d6) δ 142.36, 133.35, 127.52, 124.44, 123.98, 122.76, 115.31, 112.50, 97.17, 44.16, 29.70, 20.56, 16.94. MS: m / z (%) [M - ] calcd for C 26 H 27 Br2N2O6P2: 684.99; found: 684.97.

[0064] Example 3: Synthesis of (2,10-dibromoindolo[2,3-b]carbazole-5,7-diylbis(butan-4,1-diyl))bisphosphonic acid (5,7-IDCz) self-assembled hole transport material

[0065] The synthesis route is as follows:

[0066]

[0067] Step one:

[0068] The specific synthesis procedure for 2,10-dibromo-5,7-dihydroindolo[2,3- b]carbazole (Compound 8) was consistent with Compound 2, and resulted in a grey-green solid with NMR characterization data of 1 H NMR (400 MHz, DMSO-d6) δ 11.53 (s, 2H), 8.97 (s, 2H), 8.33 (d, J = 1.7 Hz, 2H), 7.56 - 7.47 (m, 4H). 13 C NMR (101 MHz, DMSO-d6) δ 139.68, 139.43, 128.09, 126.02, 122.75, 118.11, 113.61, 112.49, 111.67.

[0069] Step Two:

[0070] The specific synthesis procedure for 2,10-dibromo-5,7-dihydroindolo[2,3- b]carbazole (Compound 8) was consistent with Compound 2, and resulted in a grey-green solid with NMR characterization data of 1 H NMR (400 MHz, DMSO-d6) δ 9.02 (d, J = 9.3 Hz, 2H), 8.31 (d, J = 1.5 Hz, 2H), 7.62 (d, J = 6.6 Hz, 4H), 4.83 - 4.74 (m, 4H), 3.56 - 3.35 (m, 4H), 1.91 - 1.77 (m, 8H). 13 C NMR (101 MHz, DMSO-d6) δ 141.62, 138.34, 128.64, 124.71, 122.48, 119.99, 117A1, 114.10, 112.56, 44.44, 35.21, 29.92, 29.14.

[0071] Step Three:

[0072] The specific synthesis procedure for (2,10-dibromoindolo[2,3-b]carbazole-5,7- diylbis(butan-4,1-diyl))bisphosphonic acid (5,7-IDCz) was consistent with Compound 9, 9-DCz, and resulted in a dark green solid. The NMR characterization data was 1 H NMR (400 MHz, DMSO-d6) δ 8.82 (s, 2H), 8.30 (s, 2H), 7.62 (s, 4H), 3.79 (q, J = 5.7 Hz, 4H), 1.86 (s, 4H), 1.18 (q, J = 5.4, 4.3 Hz, 8H). 13C NMR (101 MHz, DMSO-d6) δ 142.36, 138.50, 128.87, 124.94, 122.67, 119.80, 118.00, 115.05, 112.72, 42.91, 29.55, 20.72, 16.81. MS: m / z (%) [M - ] calcd for C 26 H 27 Br2N2O6P2: 684.97; found: 684.97.

[0073] Example 4: Preparation of perovskite solar cell based on self-assembled monolayer

[0074] (1) ITO conductive glass pretreatment

[0075] The customized ITO glass was sequentially washed with glass detergent, deionized water, ethanol for 20 minutes each, and then dried with a nitrogen gun. After that, it was placed in a glass petri dish and treated in ultraviolet-ozone (UV-Ozone) for 15 minutes to remove the last organic residues. Then, it was transferred to a nitrogen glove box for standby.

[0076] (2) Preparation of hole transport layer solution and film

[0077] The synthesized self-assembled molecule was dissolved in ethanol solution (0.5 mg / ml). 30 μL of this solution was spin-coated on the treated ITO glass at 3000 rpm for 30 seconds, and then immediately placed on a hot stage at 100°C for annealing for 10 minutes.

[0078] (3) Preparation of perovskite precursor solution and film

[0079] 221.3 mg of lead iodide, 264.2 mg of lead bromide, 165.1 mg of formamidinium hydroiodide, and 62.4 mg of cesium iodide were dissolved in 1 ml of a mixed solution of N, N-dimethylformamide: dimethyl sulfoxide (v:v = 4:1). This solution was placed on a magnetic stirrer and stirred overnight. Before use, it was filtered with a 0.22 μm organic filter. 30 μL of this solution was spin-coated on the previously prepared device at 1000 rpm for 10 seconds, followed by 4000 rpm for 40 seconds. At 20 seconds before the end of spin-coating, 150 μL of chlorobenzene solution was added dropwise to the perovskite surface. Immediately after the end of spin-coating, it was placed on a hot stage at 100°C for annealing for 10 minutes.

[0080] (4) Preparation of interface layer solution and film

[0081] 0.5 mg ethylenediamine dihydroiodide was dissolved in 1 ml isopropanol solution. 35 μL prepared solution was spin-coated on the perovskite layer surface at 4000 rpm for 20 seconds, and then placed on a hot stage at 90°C for annealing for 5 minutes.

[0082] (5) Preparation of electron transport layer and silver electrode

[0083] The prepared film was placed in an evaporation chamber, vacuumed to less than 10 -4 Pa, and 20 nm thick C 60 7 nm thick BCP were evaporated on the film layer by layer. Finally, 90 nm thick Ag electrode was evaporated to complete the preparation of the device, and the effective area of the device was 0.0396 cm 2 .

[0084] The prepared device structure is shown in Figure 25 Using a solar simulator, the light source intensity was AM 1.5G, 100 mW cm -2 The open-circuit voltage, short-circuit current and fill factor of the prepared device were tested. The parameters of the perovskite solar cell device obtained according to this method are shown in Table 1.

[0085] Table 1: Device measurement results of the perovskite solar cell prepared using self-assembled molecules:

[0086] Battery device V OC (V)]]> J SC (mA / cm 2 )]]> FF (%) PCE (%) 4PACz 1.295 18.15 80.40 18.90 5,7-IDCz 1.309 18.26 81.92 19.58 5,11-IDCz 1.311 18.35 82.74 19.90 9,9-DCz 1.334 18.54 83.97 20.77

[0087] The applicant states that the present application is illustrated by the above-mentioned embodiments to show the detailed structural features of the present application, but the present application is not limited to the above-mentioned detailed structural features, i.e. it does not mean that the present application must rely on the above-mentioned detailed structural features to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of the components selected by the present application, addition of auxiliary components, selection of specific modes, etc. fall within the protection scope and disclosure scope of the present application.

[0088] The preferred embodiments of the present application are described in detail above, but the present application is not limited to the specific details in the above-mentioned embodiments, and within the technical concept scope of the present application, various simple modifications can be made to the technical solutions of the present application, and these simple modifications all belong to the protection scope of the present application.

Claims

1. A self-assembled monolayer hole transport material based on carbazole derivatives, characterized in that: having the following structural formula: In the formula, R1=- C 2H4-, -C3H6-, -C4H8-, -C6H 12 -; R2 = F, Cl, Br.I.

2. The self-assembled monolayer hole transport material of claim 1, wherein: The self-assembled monolayer hole transport material based on carbazole derivatives is applied to a trans-wide band gap perovskite solar cell.

3. Use of the self-assembled monolayer hole transport material according to claim 1, characterized in that: The structure of the perovskite solar cell is ITO / HTL / perovskite / C 60 / BCP / Ag, the HTL is a self-assembled monolayer hole transport material based on a carbazole derivative.

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