Perovskite solar cell and preparation method thereof

Abstract

The application discloses a perovskite solar cell and a preparation method thereof, the perovskite solar cell has a hole transport layer, and a material of the hole transport layer is an organic molecular material with a central unit of a benzodithiophene substituted by a dimethylthio-diphenylamine or triphenylamine as an end group and an alkoxy group or a thiophene group. The application provides an organic small molecular material which replaces PTAA without an additive and a surface treatment process, and improves the stability of a corresponding device while improving photoelectric conversion efficiency.

Description

Technical Field

[0001] This invention belongs to the field of solar photovoltaic device technology, specifically relating to a perovskite solar cell and its preparation method. Background Technology

[0002] In recent years, organic-inorganic perovskite solar cells (PSCs) have developed rapidly. Over the past decade, scientists have conducted in-depth research and exploration of perovskite solar cells, and the efficiency of this type of cell has now exceeded 25% (H. Min, T. J. Shin, S. Seok et al. Perovskite solar cells with atomically coherent interlayers on SnO2 electrodes, Nature, 2021, 598, 444-450). In PSCs, hole transport materials (HTMs) play a crucial role in extracting and transporting holes from the perovskite active layer to the counter electrode. Among them, the polymer PTAA (poly(4-phenylene)(2,4,6-trimethylphenyl)amine) is currently the commercially available standard hole transport material for planar PSCs. PSCs based on PTAA can achieve a maximum efficiency of 22%, but obtaining high efficiency often requires surface wetting treatment of PTAA or the addition of dopants to improve its hole extraction and transport efficiency. However, the presence of additives can significantly affect the stability of the device, which is detrimental to the commercial development of perovskite solar cells. Summary of the Invention

[0003] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0004] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0005] One objective of this invention is to provide a perovskite solar cell that replaces PTAA with an organic small molecule material that does not require additives or surface treatment processes, thereby improving photoelectric conversion efficiency and enhancing the stability of the corresponding device.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a perovskite solar cell, wherein the perovskite solar cell has a hole transport layer, and the material of the hole transport layer is an organic molecular material with benzo[a]thiophene substituted with alkoxy or thiophene groups as the central unit, using dimethylthio-diphenylamine or triphenylamine as the end group.

[0007] As a preferred embodiment of the perovskite solar cell of the present invention, the material of the hole transport layer includes one of the organic molecular materials shown in Formula I or Formula II;

[0008]

[0009] As a preferred embodiment of the perovskite solar cell of the present invention, wherein: the material of the hole transport layer is an organic molecular material shown in Formula I, and the thickness of the hole transport layer is 8-15 nm;

[0010] The hole transport layer is made of an organic molecular material as shown in Formula II, and the thickness of the hole transport layer is 5-8 nm.

[0011] As a preferred embodiment of the perovskite solar cell of the present invention, wherein: the perovskite solar cell uses CH3NH3PbI 3-x Cl x It is a perovskite active layer.

[0012] In a preferred embodiment of the perovskite solar cell of the present invention, the perovskite solar cell further includes a conductive glass substrate, the hole transport layer is located on the surface of the conductive glass substrate, the perovskite active layer is located on the surface of the hole transport layer, and an electron transport layer, a blocking layer and an Ag electrode are sequentially disposed on the perovskite active layer.

[0013] Another object of the present invention is to provide a method for fabricating a perovskite solar cell, comprising,

[0014] Provide materials for the hole transport layer;

[0015] The hole transport layer material is spin-coated onto the substrate electrode and then annealed.

[0016] In a preferred embodiment of the method for preparing the perovskite solar cell of the present invention, the material of the spin-coated hole transport layer is an organic molecular material of formula I dissolved in an organic solvent at a concentration of 5-15 mg / mL; or an organic molecular material of formula II dissolved in an organic solvent at a concentration of 3-10 mg / mL.

[0017] In a preferred embodiment of the method for preparing the perovskite solar cell of the present invention, the material of the spin-coated hole transport layer is an organic molecular material of Formula I dissolved in an organic solvent at a concentration of 10 mg / mL; or an organic molecular material of Formula II dissolved in an organic solvent at a concentration of 5 mg / mL.

[0018] In a preferred embodiment of the method for preparing perovskite solar cells of the present invention, the annealing treatment is performed at a temperature of 100–175°C for a time of 5–15 min.

[0019] In a preferred embodiment of the method for preparing perovskite solar cells according to the present invention, the annealing treatment is performed at a temperature of 150°C for a time of 5 minutes.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention discloses the structures of two organic molecular materials, selecting benzodithiophene (oxy-alkyl or thiophene-alkyl substituted) as the central unit, with bis(methylthio)-diphenylamine or triphenylamine symmetrically connected at both ends. The organic molecular materials are used as hole transport layers in perovskite solar cells. This invention provides a small organic molecule material that can replace PTAA without the need for additives or surface treatment processes, thereby improving the photoelectric conversion efficiency and the stability of the corresponding device, and providing sufficient material options for the commercialization of perovskite solar cells. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0023] Figure 1 The image shows the ultraviolet photoelectron spectrum of the inverted perovskite solar cell device based on BDTO-MTP as the undoped hole transport layer in Embodiment 1 of the present invention.

[0024] Figure 2 The image shows the ultraviolet photoelectron spectrum of the inverted perovskite solar cell device based on BDTT-PMTP as the undoped hole transport layer in Embodiment 2 of the present invention.

[0025] Figure 3 This is a schematic diagram of the structure of the inverted perovskite solar cell device in Embodiment 3 of the present invention;

[0026] Figure 4 The figures are current-voltage curves of the optimal devices with undoped hole transport layers BDTO-MTP and BDTT-PMTP in Embodiment 3 of the present invention; wherein, (A) is based on BDTO-MTP as an undoped hole transport layer, and (B) is based on BDTT-PMTP as an undoped hole transport layer. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0029] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0030] The raw materials used in the examples were prepared by the method reported in the reference (Journal of Polymer Science, Part A: Polymer Chemistry, 48(8), 1822-1829; 2010); monomer M1 was prepared by the method reported in the reference (J. Phys. Chem. C 2017, 121, 40, 21821–21826); monomer M3 was prepared by the method reported in the reference (ACS Applied Materials & Interfaces, 10(26), 22495-22503; 2018); and monomer M4 was prepared by the method reported in the reference (Chemical Engineering Journal 433(2022) 133265). All other materials, unless otherwise specified, were commercially purchased.

[0031] Example 1

[0032] This embodiment 1 provides a method for synthesizing BDTO-MTP, the specific steps of which are as follows:

[0033] Add 20 ml of toluene to a flask, then add monomers M1 (1 equivalent, 0.9 g, molecular weight 604.5, 1.5 mmol), M2 (2.5 equivalent, 1.0 g, molecular weight 261, 9.6 mmol), tris(dibenzylacetone)dipalladium (0.02 equivalent, 30 mg, molecular weight 915, 6.6 × 10⁻⁴ mmol), tri-tert-butylphosphonium tetrafluoroborate (0.03 equivalent, 15 mg, molecular weight 290, 1.6 × 10⁻³ mmol), and sodium tert-butoxide (3 equivalent, 0.44 g, molecular weight 96, 13.8 mmol) sequentially to the flask. Stir the reaction mixture in a 120°C oil bath for 12 hours. After cooling, extract the solution 2 to 3 times with distilled water and dichloromethane solution. Wash the extracted organic phase 2 to 3 times with saturated brine, and remove moisture with excess anhydrous magnesium sulfate. Purification was performed using a neutral alumina chromatography column with a 2:1 (v / v) petroleum ether / dichloromethane eluent. The product was dissolved in acetone and then recrystallized from methanol. The product was filtered under vacuum and washed several times with methanol to obtain a pale yellow solid (0.62 g, yield 43.04%), named BDTO-MTP.

[0034] The synthetic route is as follows:

[0035]

[0036] The compound was characterized using mass spectrometry. C 54 H 64 O2N2S6 Exact Mass(964.33),MS(MADI-TOF)(964.5).

[0037] The structural confirmation data is as follows: 1 H NMR(500MHz, chloroform-d)δ(ppm):7.24-7.22(d,8H),7.22-7.20(d,8H),6.83-6.81(s,2H),3.98-3.96(s,4H),2.50- 2.48(s,12H),1.64-1.60(m,2H),1.56-1.54(s,2H),1.50-1.40(m,8H),1.26-1.22(m,8H),0.87-0.80(m,12H).

[0038] The obtained BDTO-MTP is well soluble in common solvents such as chloroform, toluene and chlorobenzene.

[0039] BDTO-MTP was dissolved in chlorobenzene at a concentration of 10 mg / ml and then suspended on an ITO conductive glass substrate at 5000 rpm. After the operation, the film was annealed at 150 °C for 5 min. The resulting film was then subjected to ultraviolet photoelectron spectroscopy (UPS). The UPS spectrum of BDTO-MTP is shown below. Figure 1 As shown.

[0040] According to the formula Φ=21.2-(E cut off -E i )from Figure 1 The HOMO level of BDTO-MTP was obtained as -5.23 eV, and then determined by the formula... This indicates that the energy levels of BDTO-MTP can be used as hole transport layers in photovoltaic devices.

[0041] Example 2

[0042] This embodiment 2 provides a method for synthesizing BDTT-PMTP, the specific steps of which are as follows:

[0043] Add 20 mL of toluene to a flask, then add monomers M3 (1 equivalent, 0.9 g, molecular weight 905, 0.99 mmol), M4 (2.6 equivalent, 1.1 g, molecular weight 261, 11 mmol), tris(dibenzylacetone)dipalladium (0.13 equivalent, 120 mg, molecular weight 915, 0.017 mmol), and triphenylphosphine (0.26 equivalent, 80 mg, molecular weight 304, 0.068 mmol). Stir the mixture in a 120°C oil bath for 12 hours. After cooling, extract the organic phase 2-3 times with distilled water and dichloromethane solution. Wash the extracted organic phase 2-3 times with saturated brine. Remove water with excess anhydrous magnesium sulfate. Purify the product using a neutral alumina chromatography column with a 3:1 (v / v) petroleum ether / dichloromethane eluent. Dissolve the product in dichloromethane and recrystallize it using methanol solution. The sample was filtered using a vacuum pump and then washed several times with methanol to obtain a yellow solid target product (0.51 g, yield 41.13%), which was named BDTT-PMTP.

[0044] The synthetic route is as follows:

[0045]

[0046] The compound was characterized using mass spectrometry. C 74 H 76 N2S8 Exact Mass(1248.38),MS(MADI-TOF)(1248.9).

[0047] The structural confirmation data is as follows: 1H NMR (500MHz, chloroform-d) δ (ppm): 7.74-7.72 (s, 2H), 7.56-7.52 (m, 4H), 7.33-7.32 (d, 2H), 7.20-7.17 (m, 8H), 7.05-7.02 (m, 12H), 6.91-6.90 (d, 2 H),2.88-2.86(d,4H),2.48-2.46(s,12H),1.73-1.66(m,2H),1.56-1 .54(s,2H),1.44-1.32(m,8H),1.26-1.24(s,2H),0.97-0.88(m,12H).

[0048] The obtained BDTT-PMTP is well soluble in common solvents such as chloroform, toluene and chlorobenzene.

[0049] BDTT-PMTP was dissolved in chlorobenzene at a concentration of 5 mg / ml and then suspended and coated onto an ITO conductive glass substrate at 5000 rpm. After the process, the film was annealed at 150 °C for 5 min. The resulting film was then subjected to ultraviolet photoelectron spectroscopy (UPS). The UPS spectrum of BDTT-PMTP is shown below. Figure 2 As shown.

[0050] According to the formula Φ=21.2-(E cut off -E i )from Figure 2 The HOMO level of BDTT-PMTP was obtained as -5.17 eV, and then determined by the formula... This indicates that the energy levels of BDTT-PMTP can be used as hole transport layers in photovoltaic devices.

[0051] Example 3

[0052] Fabrication based on CH3NH3PbI using BDTO-MTP and BDTT-PMTP as hole transport layers 3-x Cl x Inverted perovskite solar cell. A schematic diagram of the inverted device structure is shown below. Figure 3 As shown. The perovskite solar cell inverted device prepared in this embodiment consists of, from bottom to top, an ITO conductive glass substrate 100, a hole transport layer 200, a perovskite active layer 300, an electron transport layer 400, a barrier layer 500, and an Ag electrode 600.

[0053] The fabrication method of the inverted device is as follows:

[0054] (1) The BDTO-MTP obtained in Example 1 and the BDTT-PMTP obtained in Example 2 were dissolved in chlorobenzene to prepare BDTO-MTP solutions with concentrations of 5 mg / mL, 10 mg / mL and 15 mg / mL, and BDTT-PMTP solutions with concentrations of 3 mg / mL, 5 mg / mL and 10 mg / mL, respectively.

[0055] (2) The ITO conductive glass substrate was ultrasonically washed with detergent, deionized water, ethanol, acetone and isopropanol for 15 min in sequence, dried with dry air and treated with UVO for 20 min.

[0056] (3) Spin-coat the hole transport material BDTO-MTP solution or BDTT-PMTP solution obtained in step (1) on the ITO conductive glass substrate at 5000 rpm for 30 s spin coating time, followed by annealing at 150 ℃ in a glove box for 5 min to obtain the hole transport layer.

[0057] (4) After spin-coating PdI2 material at 3500 rpm for 20 s on the hole transport layer, CH3NH3I was added dropwise. After the operation was completed, the material was annealed at 70℃ for 3 min, followed by annealing at 100℃ for 3 min to obtain the perovskite active layer.

[0058] (5) 20 nm C was deposited sequentially on the perovskite layer by evaporation. 60 As an electron transport layer, and an 8nm BCP as a barrier layer.

[0059] (6) At 2.0×10 -6 A perovskite solar cell was obtained by thermally evaporating an 80 nm thick silver electrode onto the hole layer under a pressure of Pa, with a maximum effective area of ​​0.0757 cm². 2 .

[0060] Using an AM1.5G intensity (100mW / cm²) of a xenon lamp solar simulator in a glove box filled with N2. 2 The open-circuit voltage, short-circuit current, and fill factor of the prepared perovskite solar cell device were tested under the xenon lamp solar simulator, which was calibrated using silicon diodes (with KG5 visible filters) at the National Renewable Energy Laboratory (NREL).

[0061] The perovskite solar cell device was prepared using PTAA as the hole transport layer without any modification layer. The preparation method was basically the same as the above preparation method, except that the material was replaced with 2 mg / ml PTAA in step (1), and the other steps were the same. The inverted perovskite solar cell device prepared was used as a reference device.

[0062] Table 1 shows a performance comparison of perovskite solar cell devices with different concentrations of BDTO-MTP and BDTT-PMTP hole transport materials, as well as a perovskite solar cell device with no modification layer based on the PTAA hole transport layer.

[0063] Table 1

[0064]

[0065]

[0066] As can be seen from the data in Table 1, the optimal device for the inverted perovskite solar cell based on BDTO-MTP as the undoped hole transport layer is obtained at a concentration of 10 mg / mL, with an open-circuit voltage of 1.07 V and a short-circuit current of 22.88 mA / cm². 2 The fill factor is 79.70%, and the energy conversion efficiency is 19.54%. The current-voltage curve of the optimal device is as follows: Figure 4 As shown in Figure A.

[0067] The optimal inverted perovskite solar cell device based on BDTT-PMTP as the undoped hole transport layer was obtained at a concentration of 5 mg / mL, exhibiting an open-circuit voltage of 1.09 V and a short-circuit current of 22.85 mA / cm². 2 The fill factor is 84.56%, and the energy conversion efficiency is 21.08%. The current-voltage curve of the optimal device is as follows: Figure 4 As shown in B.

[0068] In contrast, the reference device based on PTAA as the hole transport layer without a modification layer has an open-circuit voltage of 1.06V and a short-circuit current of 22.10mA / cm. 2 The fill factor is 78.70%, and the energy conversion efficiency can only reach 18.58%.

[0069] Example 4

[0070] Based on Example 3, in this Example 4, the optimal device concentrations of BDTO-MTP and BDTT-PMTP were selected in step (1), and the annealing temperature in step (3) was adjusted. The annealing time was 5 minutes. The performance of the obtained perovskite solar cell device was tested according to the test method of Example 3. The results are shown in Table 2.

[0071] Table 2

[0072]

[0073]

[0074] As can be seen from the data in Table 2, in the fabrication of perovskite solar cell inverted devices with undoped hole transport layers based on BDTO-MTP or BDTT-PMTP, if annealing is not performed in step (3), the perovskite solar cell inverted device will break down during testing. As the annealing temperature gradually increases to 150℃, the performance of the perovskite solar cell inverted device gradually improves. However, when the annealing temperature is further increased to 175℃, the performance decreases. Therefore, the optimal annealing temperature is 150℃.

[0075] Example 5

[0076] Based on Example 3, in this Example 5, the optimal device concentrations of BDTO-MTP and BDTT-PMTP were selected in step (1), and the annealing time in step (3) was adjusted. The annealing temperature was 150℃. The performance of the obtained perovskite solar cell device was tested according to the test method of Example 3. The results are shown in Table 3.

[0077] Table 3

[0078]

[0079]

[0080] As can be seen from the data in Table 3, in the fabrication of perovskite solar cell inverted devices based on BDTO-MTP or BDTT-PMTP as the undoped hole transport layer, increasing the annealing time is not conducive to improving performance at the same annealing temperature. Therefore, the optimal annealing time is 5 min.

[0081] This invention synthesizes novel organic molecular materials BDTO-MTP and BDTT-PMTP by using benzodithiophene (oxy-alkyl or thiophene-alkyl substituted) as the central unit and symmetrically connecting dimethylthio-diphenylamine or triphenylamine at both ends. These materials are spin-coated onto ITO glass electrodes as hole transport layers, serving both hole extraction and transport functions. Furthermore, they achieve passivation by interacting with free lead ion defects in perovskite crystals through the interaction of the sulfur atoms in the oxygen or thiophene groups and the methylthio group. The organic molecular materials BDTO-MTP and BDTT-PMTP exhibit good solubility in common organic solvents (such as dichloromethane, trichloromethane, toluene, chlorobenzene, etc.), allowing for the preparation of high-quality thin films using solution methods, while also possessing suitable HOMO energy levels. BDTO-MTP and BDTT-PMTP are then applied as hole transport layers to CH3NH3PbI 3-x Cl xThe highest power conversion efficiencies of the perovskite solar cells are 19.54% and 21.08%, respectively, while the highest power conversion efficiency of the device using undoped and unmodified PTAA is 18.58%.

[0082] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A perovskite solar cell, characterized in that: The perovskite solar cell has a hole transport layer, and the material of the hole transport layer is an organic molecular material with benzodithiophene as the central unit, with dimethylthio-diphenylamine or triphenylamine as the end group and alkoxy or thiophene groups as the substituted end group. The material of the hole transport layer includes one of the organic molecular materials shown in Formula I or Formula II; (Formula I) (Formula II); The perovskite solar cell uses CH3NH3PbI 3-x Cl x It is a perovskite active layer.

2. The perovskite solar cell as described in claim 1, characterized in that: The hole transport layer is made of an organic molecular material as shown in Formula I, and the thickness of the hole transport layer is 8~15 nm. The hole transport layer is made of an organic molecular material as shown in Formula II, and the thickness of the hole transport layer is 5~8 nm.

3. The perovskite solar cell as described in claim 1, characterized in that: The perovskite solar cell further includes a conductive glass substrate (100), a hole transport layer (200) located on the surface of the conductive glass substrate (100), a perovskite active layer (300) located on the surface of the hole transport layer (200), and an electron transport layer (400), a barrier layer (500) and an Ag electrode (600) are sequentially disposed on the perovskite active layer (300).

4. A method for preparing a perovskite solar cell as described in claim 1, characterized in that: include, Materials for the hole transport layer; The hole transport layer material is spin-coated onto the substrate electrode and then annealed.

5. The method for preparing a perovskite solar cell as described in claim 4, characterized in that: The material for the spin-coated hole transport layer is an organic molecular material of Formula I, which is dissolved in an organic solvent at a concentration of 5-15 mg / mL; or an organic molecular material of Formula II, which is dissolved in an organic solvent at a concentration of 3-10 mg / mL.

6. The method for preparing a perovskite solar cell as described in claim 5, characterized in that: The material for the spin-coated hole transport layer is an organic molecular material of Formula I dissolved in an organic solvent at a concentration of 10 mg / mL; or an organic molecular material of Formula II dissolved in an organic solvent at a concentration of 5 mg / mL.

7. The method for preparing a perovskite solar cell according to any one of claims 4 to 6, characterized in that: The annealing process is carried out at a temperature of 100~175 ℃ for 5~15 min.

8. The method for preparing a perovskite solar cell as described in claim 7, characterized in that: The annealing process is performed at a temperature of 150 °C for 5 min.

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