Indolocarbazole self-assembly molecule mixture, hole transport material, perovskite solar cell and photovoltaic module

Abstract

The present application relates to the technical field of perovskite solar cells, in particular to an indolocarbazole self-assembled molecule mixture, a hole transport material, a perovskite solar cell and a photovoltaic module. The indolocarbazole self-assembled molecule mixture comprises at least two kinds of compounds with different carbon chain lengths in a compound group formed by a compound shown in the following structural formula, wherein n is any value between 2 and 7. The indolocarbazole self-assembled molecule mixture can be used as a hole transport material, thereby avoiding the accumulation and aggregation phenomenon caused by the use of SAMs molecules alone, making the self-assembled molecule layer formed more uniform, ordered and compact, avoiding the formation of multiple molecular layers in local, and enabling the perovskite energy level and the transport layer energy level to be more matched, which is conducive to the rapid extraction of carriers and thereby improves the performance of the perovskite solar cell.

Description

Technical Field

[0001] This invention relates to the field of perovskite solar cell technology, and more specifically, to indo-carbazole self-assembled molecular mixtures, hole transport materials, perovskite solar cells, and photovoltaic modules. Background Technology

[0002] Self-assembled molecules (SAMs) hold great potential for application in perovskite solar cells, especially since the hole transport layer they form can not only modulate the work function of the substrate but also minimize parasitic absorption and consumption. Therefore, further development and research of SAMs are needed. SAMs mainly consist of functional groups, linking groups, and anchoring groups. They achieve self-assembly through dehydration reactions between their own anchoring groups and the hydroxyl groups on the surface of TCO metal oxides, as well as the π-π stacking of their terminal aromatic ring structures, ultimately achieving the aforementioned effects. The length and orientation of the linking groups in SAMs play a crucial role in regulating the interaction strength between the functional groups and the anchoring groups, providing flexibility for optimizing conformation during molecular assembly.

[0003] However, existing SAMs molecules have limited solubility, poor wettability, and are prone to clustering, exhibiting weak stability and self-limiting chemical reactions. Therefore, SAMs materials tend to be unevenly distributed when anchoring to the substrate, failing to form a high-density, tightly packed self-assembled molecular layer. This results in unstable interfacial properties and affects device efficiency. Even with structural optimization and improvements to existing SAMs, when used alone, they still cannot completely cover the entire conductive substrate, leading to localized multilayer stacking, high resistance, and direct contact between the perovskite film and the conductive substrate. This, in turn, causes localized leakage and perovskite decomposition, resulting in performance degradation of perovskite solar cells.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide indole-carbazole self-assembled molecular mixtures, hole transport materials, perovskite solar cells, and photovoltaic modules. Embodiments of this invention provide a novel indole-carbazole self-assembled molecular mixture that can serve as a hole transport material, thereby avoiding the stacking and aggregation phenomena caused by using SAMs molecules alone. This results in a more uniform, ordered, and compact arrangement of the self-assembled molecular layers, preventing the formation of multiple molecular layers in certain areas. This allows for a better match between the perovskite valence band edge and the transport layer energy level, facilitating rapid carrier extraction and thus improving the performance of perovskite solar cells.

[0006] The present invention is implemented as follows:

[0007] This invention provides an indolocarbazole self-assembled molecular mixture comprising at least two compounds of different carbon chain lengths formed by compounds shown in the following structural formulas. Where n is any value between 2 and 7.

[0008] In an optional embodiment, it includes any two compounds from the group consisting of compounds with different carbon chain lengths formed by the compounds shown in the following structural formulas.

[0009] Where n is any value between 2 and 7;

[0010] In an optional embodiment, the molar ratio of the compound with a relatively short carbon chain length to the compound with a relatively long carbon chain length in the group of compounds with different carbon chain lengths is (4:1) to (1:4).

[0011] In an optional embodiment, it includes at least two compounds of different carbon chain lengths formed by compounds shown in the following structural formulas.

[0012]

[0013] In an optional embodiment, it includes any two compounds from the group consisting of compounds with different carbon chain lengths formed by the compounds shown in the following structural formulas.

[0014]

[0015] In an optional implementation, it includes

[0016]

[0017] The molar ratio of the compound shown in Formula 1 to the compound shown in Formula 3 is (4:1)-(1:4).

[0018] In a second aspect, the present invention provides a hole transport material comprising the indole-carbazole self-assembled molecule mixture described in the foregoing embodiments.

[0019] Thirdly, the present invention provides a perovskite solar cell comprising a hole transport layer formed of the hole transport material described in the foregoing embodiments.

[0020] Fourthly, the present invention provides a photovoltaic module comprising the perovskite solar cell described in the foregoing embodiments.

[0021] The present invention has the following beneficial effects: By combining indole-carbazole self-assembled molecules with carbon chains of different lengths as connecting groups to form a mixture, the invention avoids the stacking and aggregation phenomena caused by using indole-carbazole self-assembled molecules alone. This results in a more uniform, ordered, and compact arrangement of the self-assembled molecular layers, preventing the formation of multi-layered structures in certain areas. This facilitates the extraction of hole carriers and allows for stronger bonding with surface hydroxyl groups such as TCO, thus anchoring them well to the conductive substrate surface and forming a denser, more uniform hole transport layer, thereby improving the performance of perovskite solar cells. Simultaneously, it enables a better match between the perovskite valence band edge and the transport layer energy levels, facilitating rapid carrier extraction and further improving the efficiency of perovskite solar cells. Furthermore, the remaining phosphate groups in the indole-carbazole self-assembled molecule mixture, acting as hydrophilic groups, effectively improve the surface wettability of the hole transport layer, making it easier to form a dense, high-quality perovskite film, enhancing the stability of perovskite solar cells, and improving their efficiency. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A schematic diagram of the structure of a perovskite solar cell provided as an application example of the present invention;

[0024] Figure 2 A schematic diagram of the theoretical structure of a perovskite solar cell substrate provided as an application example of the present invention;

[0025] Figure 3 A graph showing the open-circuit voltage of a perovskite solar cell provided as an application example of the present invention;

[0026] Figure 4 A graph showing the current density of a perovskite solar cell provided as an application example of the present invention;

[0027] Figure 5 A graph showing the fill factor of a perovskite solar cell provided as an application example of the present invention;

[0028] Figure 6 The graph shows the efficiency results of a perovskite solar cell provided as an application example of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0030] The inventors discovered that when the indole-carbazole phosphate self-assembled molecule is used alone, the hole transport material it forms has better intrinsic conductivity and wettability compared to the hole transport material formed by [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphate (Me-4PACz). However, the inventors also found that when the indole-carbazole phosphate self-assembled molecule is used alone, it also has problems such as not being able to completely cover the entire conductive substrate, local multilayer stacking, and high resistance, which leads to direct contact between the perovskite film and the conductive substrate. Direct contact between the perovskite film and the conductive substrate causes several problems, such as (1) local leakage, (2) the conductive substrate inducing the decomposition of perovskite, causing the degradation of perovskite solar cells; the above problems mean that even with the use of improved self-assembled molecules, the performance of perovskite solar cells is still poor.

[0031] To address this issue, embodiments of the present invention provide an indole-carbazole self-assembled molecular mixture, which can effectively improve or solve the aforementioned problems.

[0032] Specifically, it includes at least two compounds from the group consisting of compounds with different carbon chain lengths formed by compounds shown in the following structural formulas.

[0033] Where n is any value between 2 and 7, for example, n is any integer between 2 and 7 such as 2, 3, 4, 5, 6 and 7.

[0034] In other words, the indole-carbazole self-assembled molecule mixture provided in the embodiments of the present invention is a mixture or composition formed by mixing at least two of the following sets: indole-carbazole self-assembled molecules with n=2, n=3, n=4, n=5, n=6, and n=7.

[0035] For example, the indole-carbazole self-assembled molecule mixture can be a composition formed by indole-carbazole self-assembled molecules with n=2 and 3, n=2 and 4, n=4 and 5, or n=4 and 7. Alternatively, it can be a composition formed by indole-carbazole self-assembled molecules with n=2, 4, and 5, n=3, 4, and 5, or n=2, 4, and 6. Alternatively, it can be a composition formed by self-assembling indole-carbazole molecules with n being 2, 3, 4, 5, and 6; or a composition formed by self-assembling indole-carbazole molecules with n being 2, 4, 5, 6, and 7; or a composition formed by self-assembling indole-carbazole molecules with n being 2, 3, 4, 5, 6, and 7.

[0036] The indole-carbazole self-assembled molecule mixture provided in this invention retains the excellent hole transport capability of the original carbon chain length indole-carbazole phosphate self-assembled molecules while mixing in indole-carbazole phosphate self-assembled molecules with longer or shorter carbon chain lengths. This mixture of indole-carbazole self-assembled molecules avoids the stacking and aggregation phenomena that occur when using individual SAMs, resulting in a more uniform, ordered, and compact arrangement of the self-assembled molecular layer. It avoids the formation of multi-layered molecules in certain areas, which is more conducive to the extraction of hole carriers. It also binds more firmly to the surface hydroxyl groups of TCOs such as ITO (FTO), thus anchoring them well to the conductive glass surface and forming a denser and more uniform hole transport layer. Furthermore, it enables a better match between the perovskite valence band edge and the transport layer energy level, which is beneficial for rapid carrier extraction. The remaining phosphate groups, as hydrophilic groups, can effectively improve the surface wettability of the hole transport layer, making it easier to form a dense, high-quality perovskite film, enhancing stability, and improving efficiency.

[0037] Specifically, in the embodiments of the present invention, the indole-carbazole self-assembled molecule mixture can be any two of the groups of compounds with different carbon chain lengths formed by the compounds shown in the above structural formula, such as the composition formed by indole-carbazole self-assembled molecules when n is 3 and 6, the composition formed by indole-carbazole self-assembled molecules when n is 3 and 4, the composition formed by indole-carbazole self-assembled molecules when n is 3 and 5, and the composition formed by indole-carbazole self-assembled molecules when n is 3 and 7.

[0038] The embodiments of the present invention are illustrated using compounds shown in the following structural formulas as examples. The indolocarbazole self-assembled molecular mixture includes at least two of the compounds shown in Formulas 1 to 3, preferably any two. For example, the indolocarbazole self-assembled molecular mixture can be a combination of compounds shown in Formula 1 and Formula 2, a combination of compounds shown in Formula 1 and Formula 3, a combination of compounds shown in Formula 2 and Formula 3, or a combination of compounds shown in Formula 1, Formula 2, and Formula 3. However, any combination of two of these compounds is more effective.

[0039] Furthermore, the molar ratio of the compound with a relatively short carbon chain to the compound with a relatively long carbon chain in the indobenzocarbazole self-assembled molecular mixture is (4:1) to (1:4), for example, any value between (4:1) and (1:4), such as 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, and 1:4. Using the above molar ratio in the raw materials of the indobenzocarbazole self-assembled molecular mixture can further improve the performance of the subsequently formed perovskite solar cells.

[0040] The proportions of each compound in the indobenzocarbazole self-assembled molecule mixture of the present invention can further improve the performance of the indobenzocarbazole self-assembled molecule mixture.

[0041] It should be noted that compounds with relatively short carbon chain lengths refer to compounds with relatively small n values ​​in the indobenzocarbazole self-assembled molecular mixture, while compounds with relatively long carbon chain lengths refer to compounds with relatively large n values ​​in the indobenzocarbazole self-assembled molecular mixture. For example, when the indobenzocarbazole self-assembled molecular mixture includes compositions formed by Formula 1 and Formula 2, the compound with relatively short carbon chain length refers to the compound shown in Formula 1, and the compound with relatively long carbon chain length refers to the compound shown in Formula 2. As another example, when the indobenzocarbazole self-assembled molecular mixture includes compositions formed by Formula 2 and Formula 3, the compound with relatively short carbon chain length refers to the compound shown in Formula 2, and the compound with relatively long carbon chain length refers to the compound shown in Formula 3. Again, as another example, when the indobenzocarbazole self-assembled molecular mixture includes compositions formed by Formula 1 and Formula 3, the compound with relatively short carbon chain length refers to the compound shown in Formula 1, and the compound with relatively long carbon chain length refers to the compound shown in Formula 3.

[0042] In embodiments of the present invention, the indole-carbazole self-assembled molecular mixture includes The carbon chain of the linking group in the compound shown in Formula 1 is relatively short, which can completely fill the gaps left by the alkyl chain in the compound shown in Formula 2. Moreover, because the carbon chain of the linking group in the compound shown in Formula 1 is relatively short, its phosphate group will not affect the anchoring of the phosphate group in the compound shown in Formula 2. This results in a high-density arrangement of the SAM, which is more uniform and neat, provides better coverage of the substrate, reduces defects, and improves the crystallinity of the perovskite film. This is beneficial for the extraction of hole carriers and therefore has higher efficiency.

[0043] Furthermore, the molar ratio of the compound shown in Formula 1 to the compound shown in Formula 3 is (4:1) to (1:4). For example, it can be any value between (4:1) and (1:4), such as 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, and 1:4.

[0044] Secondly, the present invention provides a hole transport material comprising the indole-carbazole self-assembled molecule mixture described in the foregoing embodiments. This hole transport material exhibits good hole carrier extraction capability, bonds firmly to the conductive substrate, and forms a denser and more uniform hole transport layer, thereby improving the performance of perovskite solar cells.

[0045] Thirdly, the present invention provides a perovskite solar cell comprising a hole transport layer formed from the hole transport material described in the foregoing embodiments. The perovskite solar cell provided by the embodiments of the present invention has a uniform and dense hole transport layer, with a better match between the perovskite valence band edge and the transport layer energy level, enabling rapid carrier extraction. Simultaneously, the perovskite solar cell exhibits excellent surface wettability of the hole transport layer and a dense perovskite film, resulting in excellent stability and efficiency.

[0046] Fourthly, the present invention provides a photovoltaic module comprising the perovskite solar cell described in the foregoing embodiments.

[0047] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0048] Synthesis example 1

[0049] This invention provides a method for synthesizing indole[2,3b]carbazole 5,7-yldi(ethylphosphoric acid) (hereinafter abbreviated as SAM1), comprising:

[0050] Perform the synthesis according to the following synthesis path:

[0051]

[0052] Specifically, as follows:

[0053] Step 1: 5,7-Dihydro-indolo[2,3-B]carbazole (300 mg, 1.17 mmol) and NaH (140 mg, 5.83 mmol) were added to a two-necked flask equipped with a magnetic stirrer. The flask was evacuated and purged with nitrogen. DMF (6 mL) was added for dissolution, and the reaction was allowed to proceed at room temperature for 30 min. Then, diethyl 2-bromoethyl phosphate (715 mg, 2.93 mmol) was slowly added, and the reaction was allowed to proceed overnight at room temperature. The reaction was monitored by TLC. After the reaction was complete, the reaction solution was added to a saturated sodium chloride aqueous solution, extracted with ethyl acetate, and back-extracted three times with water. The organic phase was dried over anhydrous sodium sulfate, the solvent was removed by rotary evaporation, and the crude product was purified by column chromatography to obtain a yellow solid intermediate 1 (410 mg).

[0054] The characterization data of intermediate 1 are as follows: 1 H-NMR (400MHz, DMSO-d6) δ8.90(s,1H),8.19(s,2H),7.59(s,1H),7.54(d,J=8.1Hz,2H),7.46-7.40(m,2H),7.22(d,J= 7.3Hz, 2H), 4.67 (dd, J = 13.6, 7.2Hz, 4H), 3.92 (p, J = 7.2Hz, 8H), 2.40 (dt, J = 18.0, 7.2Hz, 4H), 1.10 (t, J = 7.0Hz, 12H).

[0055] Step 2: Under nitrogen protection, intermediate 1 (270 mg, 0.4623 mmol), DCM (9 mL), and trimethylbromosilane (282.93, 1.849 mmol) were added to a two-necked flask equipped with a magnetic stirrer, and the mixture was reacted overnight at room temperature. The reaction solution was pale yellow. After the reaction was complete, 5 mL of methanol was added to the reaction solution and the mixture was stirred for another 5 hours. Then, the solvent was evaporated, methanol was added to dissolve the solid, water was added to precipitate the solid, the solid was filtered, dried, and recrystallized from DCM (20 mL) and ethanol (0.5 mL). The crystallization was then filtered, dried, and the product SAM1 was obtained as 160 mg.

[0056] The characterization data of product SAM1 are as follows: 1 H-NMR (400MHz, DMSOd6) δ8.87(s,1H),8.19(d,J=7.6Hz,2H),7.64(s,1H),7.51(d,J=8.1H z, 2H), 7.42 (t, J = 7.6Hz, 2H), 7.21 (t, J = 7.4Hz, 2H), 4.70-4.59 (m, 4H), 2.21-2.04 (m, 4H).

[0057] Synthesis example 2

[0058] This invention provides a method for synthesizing indole[2,3b]carbazole 5,7-yldi(propylphosphate) (hereinafter abbreviated as SAM2), comprising:

[0059] Perform the synthesis according to the following synthesis path:

[0060]

[0061] Specifically as follows:

[0062] Step 1: 5,7-Dihydro-indolo[2,3-B]carbazole (300 mg, 1.17 mmol) and NaH (140 mg, 5.83 mmol) were added to a two-necked flask equipped with a magnetic stirrer. The flask was evacuated and purged with nitrogen. DMF (6 mL) was added for dissolution, and the reaction was allowed to proceed at room temperature for 30 min. Then, diethyl(3-bromopropyl)phosphonate (755 mg, 2.91 mmol) was slowly added, and the reaction was allowed to proceed overnight at room temperature. The reaction was monitored by TLC. After the reaction was complete, the reaction solution was added to a saturated sodium chloride aqueous solution, extracted with ethyl acetate, and back-extracted three times with water. The organic phase was dried over anhydrous sodium sulfate, the solvent was removed by rotary evaporation, and the crude product was purified by column chromatography to obtain a yellow-green solid intermediate 2 (400 mg).

[0063] The characterization data of intermediate 2 are as follows: 1 H-NMR (400MHz, CDCl3d6) δ8.74(s,1H),8.17(s,2H),7.44(d,J=4.0Hz,4H),7.37(s,1H),7.26(s,2H),4.50(d,J=7.1Hz ,4H), 4.07(td,J=7.4,3.1Hz,9H), 2.29(dq,J=14.8,7.5Hz,4H), 1.83(dd,J=16.9,9.0Hz,4H), 1.28(t,J=7.1Hz,12H).

[0064] Step 2: Under nitrogen protection, intermediate 2 (400 mg, 0.6536 mmol), DCM (12 mL), and trimethylbromosilane (400 mg, 2.61 mmol) were added to a two-necked flask equipped with a magnetic stirrer. The reaction was allowed to proceed overnight at room temperature. After the reaction was complete, 6 mL of methanol was added to the reaction solution and the mixture was stirred for another 5 hours. The solvent was then evaporated, and the solution was dried to an oily state. Methanol was added to dissolve the oil, and water was added to precipitate the solid. The solid was then filtered, dried, and the product SAM2, 180 mg, was obtained.

[0065] The SAM2 characterization data are as follows: 1H-NMR (400MHz, DMSO-d6) δ8.90 (s, 1H), 8.22 (d, J = 7.6Hz, 2H), 7.84 (s, 1H), 7.61 (s, 2H), 7.42 (t, J = 7.6Hz, 2 H), 7.22 (t, J = 7.4Hz, 2H), 4.59 (t, J = 6.8Hz, 4H), 2.09 (dt, J = 15.0, 7.4Hz, 4H), 1.69 (dd, J = 16.3, 8.9Hz, 4H).

[0066] Synthesis example 3

[0067] This invention provides a method for synthesizing indole[2,3b]carbazole 5,7-diylbis(butane-4,1-diyl))bisphosphonic acid (hereinafter abbreviated as SAM3), comprising:

[0068] Perform the synthesis according to the following synthesis path:

[0069]

[0070] Specifically as follows:

[0071] Step 1: 5,7-Dihydro-indolo[2,3-B]carbazole (300 mg, 1.1719 mmol), 1,4-dibromobutane (10 g, 46.75 mmol), TBAB (151 mg, 0.4689 mmol), and 1.3 mL of 50% potassium hydroxide aqueous solution were added to a two-necked flask equipped with a magnetic stirrer. The reaction was carried out at 60 °C for 16 h. The reaction progress was monitored by TLC. After the reaction was completed, the mixture was cooled to room temperature, dissolved in dichloromethane, washed with water, extracted, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation. The crude product was purified by column chromatography to obtain a yellow solid intermediate 3 (450 mg).

[0072] The characterization data of intermediate 3 are as follows: 1 H-NMR (400MHz, CDCl3d6) δ8.74(s,1H),8.19(s,2H),7.41(dd,J=19.0,7.3Hz,4H),7.26(s,3H),7.20(s ,1H),4.42(t,J=7.0Hz,4H),3.43(d,J=6.4Hz,4H),2.15(p,J=7.0Hz,4H),2.00(dt,J=12.9,6.5Hz,4H).

[0073] Step 2: Under nitrogen protection, intermediate 3 (450 mg, 0.8555 mmol) was added to a two-necked flask equipped with a magnetic stirrer, and 8 mL of diethyl phosphite was added to dissolve it. The mixture was heated to 150 °C and reacted for 16 h. The reaction progress was monitored by TLC. After the reaction was completed, the mixture was cooled to room temperature, the solvent was removed by rotary evaporation, and the crude product was purified by column chromatography to obtain a pale yellow oily intermediate 4 (200 mg).

[0074] The characterization data of intermediate 4 are as follows: 1 H-NMR (400MHz, CDCl3d6) δ8.73 (s, 1H), 8.17 (d, J = 7.7Hz, 2H), 7.4 (d, 4H), 7.26 (m, 2H), 7.15 (s, 1H), 4 .39 (t, J=7.1Hz, 4H), 4.04-3.94 (m, 8H), 2.16-1.99 (m, 4H), 1.73 (d, J=7.0Hz, 8H), 1.25-1.18 (m, 12H).

[0075] Step 3: Under nitrogen protection, intermediate 4 (200 mg, 0.3125 mmol), DCM (6 mL), and trimethylbromosilane (191.25 mg, 1.25 mmol) were added to a two-necked flask equipped with a magnetic stirrer, and the mixture was reacted overnight at room temperature. After the reaction was completed, 4 mL of methanol was added to the reaction solution and the mixture was stirred for another 5 hours. Then, the solvent was evaporated, methanol was added to dissolve the solid, water was added to precipitate the solid, and the solid was filtered and dried to obtain product SAM3, 105 mg.

[0076] The SAM3 characterization data are as follows: 1 HNMR(400MHz,DMSOd6)δ8.87(d,J=5.3Hz,1H),8.19(s,2H),7.73(s,1H),7.55(d,J=8.2Hz,2H),7.40(t ,J=7.6Hz,2H),7.20(t,J=7.4Hz,2H),4.49(t,J=6.7Hz,4H),1.96(p,J=6.7Hz,4H),1.68-1.51(m,8H).

[0077] Implementation Cases 1-9

[0078] Implementation Cases 1-9 each provide a self-assembled indole-carbazole molecular mixture, the specific raw materials of which are as follows:

[0079] Implementation Case 1 – The molar ratio of SAM1 to SAM2 is 8:2;

[0080] Implementation Case 2 – The molar ratio of SAM1 to SAM2 is 5:5;

[0081] Implementation Case 3 – The molar ratio of SAM1 to SAM2 is 2:8;

[0082] Implementation Case 4 – The molar ratio of SAM1 to SAM3 is 2:8;

[0083] Implementation Case 5 – The molar ratio of SAM1 to SAM3 is 5:5;

[0084] Implementation Case 6 – The molar ratio of SAM1 to SAM3 is 8:2;

[0085] Implementation Case 7 – The molar ratio of SAM2 to SAM3 is 2:8;

[0086] Implementation Case 8 – The molar ratio of SAM2 to SAM3 is 5:5;

[0087] Implementation Case 9 – The molar ratio of SAM2 to SAM3 is 8:2.

[0088] Furthermore, the preparation of the indolocarbazole self-assembled molecular mixtures in Examples 1-9 above can all be obtained by mixing the above compounds in a certain proportion.

[0089] Application examples

[0090] This application example provides a perovskite solar cell, the structural schematic of which can be found in [reference needed]. Figure 1 The specific structure is: ITO glass / hole transport layer / Cs 0.22 FA 0.78 Pb(I 0.865 Br 0.135 )3 / C 60 / BCP / Cu, where a schematic diagram of the theoretical structure of the substrate can be found in [reference needed]. Figure 2 The fabrication method of this perovskite solar cell is as follows:

[0091] Hole layer preparation: Accurately weigh the compounds of Synthetic Examples 1 to 3 (hereinafter referred to as Comparative Examples 1 to 3) and the indole-carbazole self-assembled molecule mixtures of Examples 1 to 9 to prepare 0.5 mg / mL DMF solutions to obtain hole transport material solutions. Spin-coat the hole transport material solutions onto cleaned ITO glass at a speed of 5000 rpm for 30 s. Place the ITO glass with the hole transport material solutions spin-coated on a hot stage at 100°C and heat for annealing for 10 min to form a hole transport layer.

[0092] Perovskite layer preparation: 1.4 M Cs 0.22 FA 0.78 Pb(I 0.865 Br 0.135A perovskite layer was prepared by spin-coating a DMF:DMSO (4:1) precursor solution of 3 onto a hole transport layer at 3000 rpm for 25 s. The perovskite film was then treated by a vacuum method and annealed at 100 °C for 10 min to obtain the perovskite layer.

[0093] Electron transport layer fabrication: A 20 nm thick C60 layer was deposited as the electron transport layer by thermal evaporation at a rate of 0.1 Å / s. Subsequently, a 5 nm thick BCP was deposited at a rate of 0.1 Å / s.

[0094] Electrode fabrication: In a vacuum chamber at 5 × 10⁻⁶ 4 A 100 nm thick copper electrode was deposited under high vacuum conditions.

[0095] The perovskite solar cells described above were tested using a xenon lamp solar simulator with a light source intensity of AM 1.5G and 100mW / cm². 2 The photoelectric performance of the perovskite solar cells prepared above was tested.

[0096] See results Figures 3 to 6 ,according to Figures 3 to 6 It can be known that:

[0097] (1) The highest photoelectric conversion efficiencies when using indolocarbazole self-assembled molecules alone were 19.80%, 20.09%, and 20.28%, respectively. This indicates that indolocarbazole SAM molecules with different carbon chain lengths modified by phosphate groups have a great influence on the performance of battery devices as hole transport materials. Moreover, when butyl is used alone as a linking group, the perovskite solar cells formed by it have better performance.

[0098] (2) Experiments showed that mixing SAMs with different carbon chain lengths was more efficient than using them alone. SAM2 and SAM3 performed better when used alone, and theoretically, the mixture of SAM2 and SAM3 should also be more efficient. However, experiments showed that this was not the case. Instead, the mixture of SAM1 and SAM3, which had slightly less efficient performance, was more effective. The inventors found that this was because the SAM1 molecular chain was shorter, with less bending, less steric hindrance, and more controllable direction. It could completely fill the gaps left by the alkyl chain of the SAM3 molecule. Moreover, because the SAM1 chain was shorter, its phosphate groups did not affect the anchoring of the phosphate groups of the SAM3 molecule, improving the conventional arrangement of the SAM3 molecules, resulting in a high-density arrangement of the SAMs, a more uniform and neat SAM layer, avoiding accumulation and making the anchoring of the SAM3 molecules to the substrate more secure. This improved wettability, better coverage of the substrate, reduced defects, and better crystallinity of the perovskite film. This further adjusted the work function, which was beneficial for the extraction and transport of hole carriers, resulting in the highest efficiency.

[0099] (3) By comparing the mixing ratio of raw materials, it was found that the efficiency was the highest when the molar ratio of SAM1 to SAM3 was 1:1, reaching 22.26%. The amount of the two indole-carbazole self-assembly molecules also verified that the SAM1 molecule could completely fill the gaps left by the alkyl chain of the SAM3 molecule. The two SAMs were evenly distributed, indicating that the hole transport material formed by the indole-carbazole self-assembled molecule mixture provided in the embodiments of the present invention has great advantages.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A mixture of indolocarbazole self-assembled molecules, characterized in that, It includes at least two compounds of different carbon chain lengths formed by compounds shown in the following structural formulas. Where n is any value between 2 and 7.

2. The indole-carbazole self-assembled molecular mixture according to claim 1, characterized in that, It includes any two compounds from the group consisting of compounds with different carbon chain lengths formed by the compounds shown in the following structural formulas. Where n is any value between 2 and 7.

3. The indolocarbazole self-assembled molecular mixture according to claim 2, characterized in that, The molar ratio of compounds with relatively short carbon chain lengths to compounds with relatively long carbon chain lengths in the group of compounds with different carbon chain lengths is (4:1) to (1:4).

4. The indolocarbazole self-assembled molecular mixture according to any one of claims 1-3, characterized in that, It includes at least two compounds of different carbon chain lengths formed by compounds shown in the following structural formulas.

5. The indolocarbazole self-assembled molecular mixture according to any one of claims 1-3, characterized in that, It includes any two compounds from the group consisting of compounds with different carbon chain lengths formed by the compounds shown in the following structural formulas.

6. The indolocarbazole self-assembled molecular mixture according to any one of claims 1-3, characterized in that, It includes The molar ratio of the compound shown in Formula 1 to the compound shown in Formula 3 is (4:1)-(1:4).

7. A hole transport material, characterized in that, It includes the indolocarbazole self-assembled molecule mixture according to any one of claims 1-6.

8. A perovskite solar cell, characterized in that, It includes a hole transport layer formed from the hole transport material of claim 7.

9. The perovskite solar cell according to claim 8, characterized in that, The perovskite solar cell is a tandem perovskite solar cell.

10. A photovoltaic module, characterized in that, It includes the perovskite solar cell of claim 9.

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