Preparation method of organic electron transport layer and perovskite solar cell

Abstract

The invention provides a preparation method of an organic electron transport layer and a preparation method of a perovskite solar cell. The perovskite solar cell structurally comprises an anode, a hole transport layer, a perovskite layer, the organic electron transport layer, a cathode modification layer and a cathode from bottom to top. According to the preparation method of the organic electron transport layer, an n-type small organic molecule CY4 solution is dissolved in a PCBM solution according to a certain proportion, chlorobenzene (CB) is adopted as a solution solvent, the perovskite layer is spin-coated with the solution solvent after stirring, a high-quality organic electron transport layer film is formed, and it is measured that the photoelectric conversion efficiency of a final device is 19.80%. A series of characterization results show that the CY4-doped organic electron transport layer improves the electron extraction capability between layers and inhibits carrier recombination; and meanwhile, the roughness of the PCBM film is also reduced, and the formed organic electron transport layer film more uniformly covers the perovskite layer, so that the efficiency of the cell and the environmental stability are greatly improved finally.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, and in particular relates to a method for preparing an organic electron transport layer and a method for preparing a perovskite solar cell. Background Art

[0002] Solar cells are a clean energy source. They do not produce pollutants or release harmful gases. They are environmentally friendly, energy-saving and low-carbon. The use of solar cells can significantly reduce the use of fossil fuels, reduce carbon emissions, and help improve the atmospheric environment. In addition, solar cells mainly use solar energy to generate electricity, do not consume mineral resources, do not damage the land, and also play a positive role in the protection of environmental resources. It is a device that converts light energy into electrical energy. It is mainly composed of polycrystalline silicon, that is, a silicon compound. Ordinary batteries are devices that convert chemical energy into electrical energy. They contain heavy metals, and it is these heavy metals that cause great harm to the environment.

[0003] For inverted perovskite solar cell devices, the charge transport layer plays the role of extracting and transporting free electrons from the perovskite active layer to the cathode. 61 -Butyric acid methyl ester (PCBM) is a common electron transport layer material and is widely used due to its high electron mobility and low-temperature solution process preparation. However, PCBM has limitations such as molecular agglomeration, interface non-radiative recombination, and leakage current, which will adversely affect the photovoltaic performance of perovskite solar cell devices.

[0004] In order to solve the problems existing in inverted perovskite solar cell devices, many studies have been devoted to reducing the density of trap states on the surface and grain boundaries of perovskite and regulating the arrangement of interface energy levels. Organic molecule doping PCBM is a widely used and effective modification and optimization method. By adding organic small molecules as additives to PCBM for modification and doping, it can effectively improve the interface level contact between the perovskite active layer and the electron transport layer, reduce the energy loss caused by non-radiative recombination of carriers generated by defects, and improve the energy utilization efficiency. Therefore, it is particularly important to find a dopant that can not only improve the performance and stability of the device, but also be low-cost and easy to obtain, and reduce potential harm to the environment, for the preparation of high-performance, low-cost, energy-saving and environmentally friendly planar perovskite solar cells.

[0005] Therefore, it is necessary to provide an improved technical solution to address the above-mentioned deficiencies in the prior art. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing an organic electron transport layer and a perovskite solar cell, and to improve the photoelectric conversion efficiency of the battery device, enhance the energy utilization efficiency, and reduce environmental pollution by optimizing the electron transport layer.

[0007] In order to achieve the above object, the present invention provides the following technical solutions: In a first aspect, a method for preparing an organic electron transport layer is provided, the method comprising the following steps: Step 1, dissolving the dopant CY4 in a chlorobenzene (CB) solvent, stirring and filtering to form a CY4 precursor solution; Step 2, doping the CY4 precursor solution into the PCBM solution, stirring and filtering to form a PCBM:CY4 solution; Step 3, spin coating the PCBM:CY4 solution onto a substrate, and obtaining an organic electron transport layer after curing.

[0008] In one embodiment, the concentration of the CY4 precursor solution is 1 mg / mL.

[0009] In one embodiment, in step 1, the stirring time is 12 hours; in step 2, the stirring time is 12 hours.

[0010] In one embodiment, the concentration of the PCBM:CY4 solution is 0.01-0.1 mg / mL.

[0011] In a second aspect, a method for preparing a perovskite solar cell is also provided, the preparation method comprising the following steps: Step S1, ultrasonically clean the glass substrate coated with the anode material, and treat it with an ultraviolet ozone machine to obtain a pretreated substrate substrate; Step S2, spin coating the PTAA solution on the substrate, heating at 100° C. for 10 min for annealing, and then naturally cooling to room temperature to obtain a hole transport layer; Step S3, transferring the substrate obtained in step S2 into a glove box, and spin-coating the perovskite precursor solution on the hole transport layer using a one-step anti-solvent method, heating at 100° C. for 10 min for annealing treatment to obtain a perovskite layer; Step S4, spin coating the PCBM:CY4 solution on the perovskite layer to obtain an organic electron transport layer; Step S5, spin coating the BCP solution on the organic electron transport layer to obtain a cathode modification layer; Step S6, depositing the cathode material onto the cathode modification layer by thermal evaporation under vacuum; Wherein, the organic electron transport layer is prepared by using the method for preparing the organic electron transport layer as described above.

[0012] In one embodiment, in step S3, the perovskite precursor solution is prepared by the following method: Dissolving donor A and donor B in an organic solvent, and stirring evenly to obtain the perovskite precursor solution; The donor A is methylammonium iodide (MAI), the donor B is lead iodide (PbI2), and the organic solvent is N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0013] In one embodiment, the molar ratio of the donor A to the donor B is 1:(1-2).

[0014] In one embodiment, the total mass percentage of the donor A and the donor B in the perovskite precursor solution is 35-50 wt %.

[0015] In one embodiment, in step S5, the BCP solution is spin-coated using a coating machine, the spin-coating time is 30 seconds, and the spin-coating speed is 4000 rpm.

[0016] In a third aspect, a perovskite solar cell is provided, which is prepared using the method for preparing a perovskite solar cell as described above.

[0017] The technical solution provided by the present invention has the following excellent effects: The present invention dopes a new n-type organic small molecule CY4 into the traditional electron transport layer PCBM, and prepares a highly efficient inverted perovskite solar cell by optimizing the electron transport layer, which mainly has the following excellent effects: 1. Improved the photoelectric performance of inverted perovskite solar cells. The present invention adopts a new dopant CY4 small molecule doped in the traditional electron transport layer as the electron transport layer of the perovskite solar cell. The unique dendritic shoulder chain structure of the molecule provides a tighter multi-tooth interaction and effectively inhibits the excessive aggregation of PCBM molecules, significantly improving the surface morphology of the electron transport layer, forming a uniform and dense electron transport layer film structure, optimizing the interlayer interface contact, and reducing the erosion of the perovskite layer by water and oxygen in the environment. At the same time, the interface energy level arrangement is adjusted to make it more matched with the energy level of the perovskite. At the same time, the S, O, and N groups in the CY4 molecule interact with the free Pb in the perovskite. 2+ The mutual coordination between them passivates the electron vacancy defects, thereby effectively inhibiting the interface charge recombination and reducing energy loss. Finally, the photoelectric performance of the perovskite solar cell is improved. The energy conversion efficiency of the inverted perovskite solar cell prepared by the preparation method of the present invention reaches 19.80%.

[0018] 2. The preparation method of the organic electron transport layer is simple. The present invention uses a new dopant CY4 to dope the traditional electron transport layer, and the obtained mixed solution is directly spin-coated on the perovskite layer. The operation is simple, the performance and stability of the device are improved, and the cost is low and easy to obtain, and large-area thin films can be prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. Among them: Figure 1 A schematic diagram of the structure of a perovskite solar cell according to an embodiment of the present invention; Figure 2 is the molecular structural formula of the dopant CY4 of the present invention; Figure 3 For dopant CY4 1 H NMR chemical shift pattern; Figure 4 is the mass spectrum of dopant CY4; Figure 5 The fluorescence spectra of the organic electron transport layer prepared in Example 1 and Comparative Example 1 of the present invention; Figure 6 The ultraviolet absorption spectra of the organic electron transport layers prepared in Example 1 and Comparative Example 1 of the present invention; Figure 7 The top view and cross-sectional scanning electron microscopy images of the perovskite solar cells prepared in Example 1 of the present invention and Comparative Example 1; Figure 8 The current density-voltage characteristic curves of the perovskite solar cells prepared in Example 1 of the present invention and Comparative Example 1; Fig. 9 : The contact angles of the PCBM:CY4 films prepared in Example 1 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0021] The present invention will be described in detail below in conjunction with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0022] The perovskite solar cell doped with an organic electron transport layer provided by the present invention aims at the shortcomings of the electron transport layer material [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) commonly used in the current inverted perovskite solar cells, and provides a method for preparing an inverted perovskite solar cell in which an n-type organic small molecule CY4 is doped into the organic electron transport layer, thereby improving the photoelectric performance of the cell, having simple operation, low cost, and capable of realizing large-area preparation.

[0023] like Figure 1 As shown, the structure of the perovskite solar cell device of the present invention includes from bottom to top: substrate (glass), anode (ITO), hole transport layer (PTAA), perovskite layer (MAPbI3), electron transport layer (PCBM), cathode modification layer (BCP), cathode (Ag); wherein CY4 is uniformly doped in the electron transport layer (PCBM). Figure 2 The structural formula of the dopant CY4 used in the organic electron transport layer of the present invention is shown. When used in photovoltaic devices, the performance of the devices can be improved. Figure 3 to Figure 4 The dopant CY4 is given 1 H NMR chemical shift patterns and mass spectra.

[0024] The organic electron transport layer of the present invention adopts dopant CY4 and traditional electron transport material PCBM dissolved in organic solvent to form electron transport layer solution PCBM:CY4, and spin-coated the electron transport layer solution on a sizing machine to solidify to form an electron transport layer, and the spin coating speed is 2000 rpm, so that the electron transport layer is more evenly covered on the active layer, and the close contact between the cathode and the active layer is reduced, which is used to transmit electrons and block holes, thereby reducing carrier recombination losses at the interface and improving the performance of perovskite solar cell devices. In addition, when preparing the organic electron transport layer, high temperature annealing treatment is not required, the operation is simple, and large-area preparation can be performed.

[0025] The organic electron transport layer in the present invention can also be used in other photovoltaic devices, such as organic solar cells.

[0026] The present invention provides a method for preparing a perovskite solar cell, the preparation method comprising the following steps: Step S1, ultrasonically clean the glass substrate coated with the anode material, and treat it with an ultraviolet ozone machine to obtain a pre-treated substrate substrate. The ultraviolet ozone treatment can further clean the substrate substrate and adjust the work function of the ITO glass.

[0027] In a specific embodiment of the present invention, the anode material is indium tin oxide (ITO) for collecting holes.

[0028] Step S2, spin-coating the PTAA solution on the pretreated substrate, heating at 100°C for 10 min for annealing, and then naturally cooling to room temperature to obtain a hole transport layer. Preferably, the PTAA solution is spin-coated on the pretreated substrate using a coating machine at a spin coating rate of 4000 rpm.

[0029] Step S3, moving the substrate with the hole transport layer into a glove box, spin-coating the perovskite precursor solution (MAPbI3) on the hole transport layer using a one-step anti-solvent method, quickly dripping chlorobenzene during the spin coating process to continue spin coating, heating at 100°C for 10 min for annealing treatment, and obtaining a perovskite layer, i.e., an active layer.

[0030] In a specific embodiment of the present invention, the perovskite precursor solution is prepared by the following method: Dissolving donor A and donor B in an organic solvent and stirring to obtain a perovskite precursor solution; Wherein, donor A is methylammonium iodide (MAI), and donor B is lead iodide (PbI2). Preferably, the organic solvent is N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0031] The molar ratio of donor A to donor B is 1:(1-2). In a specific embodiment of the present invention, the molar ratio of donor A to donor B is 1:1.2.

[0032] Step S4: preparing an organic electron transport layer on the perovskite layer.

[0033] In a specific embodiment of the present invention, the method for preparing an organic electron transport layer comprises the following steps: Step s41, weigh a certain amount of CY4 and dissolve it in a solvent of chlorobenzene (CB), and stir for 12 hours to form a CY4 precursor solution.

[0034] In a specific embodiment of the present invention, the concentration of CY4 solution is 1 mg / mL.

[0035] Step s42: The CY4 solution is mixed into the PCBM solution in proportion to form a mixed solution, and the mixture is stirred for 12 hours to form a PCBM:CY4 solution.

[0036] In a specific embodiment of the present invention, the concentration of the mixed solution PCBM:CY4 solution is 0.01-0.1 mg / ml (such as 0.01 mg / ml, 0.02 mg / ml, 0.04 mg / ml, 0.06 mg / ml, 0.1 mg / ml).

[0037] Step s43, spin-coat the PCBM:CY4 solution on a coating machine for 20-40 s (e.g., 20 s, 25 s, 30 s, 35 s, 40 s), and form an organic electron transport layer after curing. The rotation speed of the spin coating on the coating machine is 2000 rpm. The rotation speed is reduced when the PCBM:CY4 solution is spin-coated, and the purpose of reducing the rotation speed is to increase the thickness of the electron transport layer so that it can better and completely cover the perovskite layer.

[0038] Step S5, spin coating the BCP solution on the organic electron transport layer to obtain a cathode modification layer. Preferably, the BCP solution is spin coated on the organic electron transport layer using a spin coater for 30 s at a spin coating rate of 4000 rpm.

[0039] Step S6: depositing the cathode material onto the cathode modification layer by thermal evaporation under vacuum.

[0040] In a specific embodiment of the present invention, the cathode material is metal silver (Ag).

[0041] The preparation method of the organic electron transport layer in the present invention dissolves the n-type organic small molecule CY4 in a chlorobenzene solution of PCBM, and then spin-coats it on the perovskite layer to form a high-quality organic electron transport layer film for electron extraction and transmission, with a photoelectric conversion efficiency of 19.80%. The doping of CY4 can passivate defects in the perovskite crystal, improve the interface level contact, reduce the energy loss caused by carrier recombination, and greatly improve the efficiency and photoelectric performance of the perovskite solar cell. It is simple to operate, low cost, and can be commercially produced.

[0042] For comparative explanation, the present invention provides Examples 1-5 and Control Examples for comparative analysis. Among them, the materials and reagents used in the following Examples 1-5 and Control Examples are all commercially available products. Example 1

[0043] The method for preparing a perovskite solar cell doped with an organic electron transport layer provided in this embodiment 1 comprises the following steps: Step S1, ultrasonically clean the anode glass substrate coated with indium tin oxide (ITO) with detergent, distilled water, acetone, and ethanol for 3 times, each time for 15 minutes. After cleaning, blow dry the glass substrate and treat it in an ultraviolet ozone device for 15 minutes to obtain a pretreated substrate wafer.

[0044] Step S2: spin-coat the PTAA solution on the pretreated glass substrate, heat it at 100° C. for 10 min for annealing, and then naturally cool it to room temperature to form a hole transport layer.

[0045] Step S3, MAI and PbI2 were dissolved in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) solution at a molar ratio of 1:1.2, and stirred at room temperature for 12 h to obtain a perovskite precursor solution (MAPbI3). The perovskite precursor solution was spin-coated on the hole transport layer at a speed of 4000 rpm, and then the anti-solvent chlorobenzene solution was quickly added at the 5th second of rotation, and the dripping was completed within 2 seconds, which can promote the rapid crystallization of the perovskite layer. After annealing at 100°C for 10 minutes, a perovskite layer, i.e., an active layer, was obtained with a thickness of 300 nm.

[0046] Step S4: spin-coat the electron transport layer solution on the perovskite layer to form an organic electron transport layer, and the rotation speed of the electron transport layer spin coating is 2000 rpm. The specific steps of preparing the organic electron transport layer include: Step s41, dissolving a certain amount of CY4 in chlorobenzene to form a solution, stirring for 12 hours to form a CY4 solution, wherein the concentration of the CY4 solution is 1 mg / mL.

[0047] Step s42, mixing the CY4 solution into the PCBM solution in a certain proportion, stirring for 12 hours, and filtering with a filter head before use to form a PCBM:CY4 solution, wherein the concentration of the PCBM:CY4 solution is 0.02 mg / mL.

[0048] Step s43, spin-coating the PCBM:CY4 solution on a coating machine for 30 seconds, and forming an organic electron transport layer, namely, a PCBM:CY4 film, after curing.

[0049] Step S5: spin-coating the BCP solution on the organic electron transport layer to obtain a cathode modification layer.

[0050] Step S6: depositing cathode material Ag onto the cathode modification layer by thermal evaporation under vacuum.

[0051] The structure of the perovskite solar cell device obtained in Example 1 provided by the present invention is ITO / PTAA / MAPbl3 / PCBM:CY4 / BCP / Ag. The performance of the perovskite solar cell device was tested. Under the optimal conditions, at 100 mW / cm 2 Under simulated sunlight, the open circuit voltage is 1.08 V and the short circuit current is 22.89 mA / cm 2 , the filling factor is 80.11% and the photoelectric conversion efficiency is 19.80%. Example 2

[0052] The method for preparing a perovskite solar cell doped with an organic electron transport layer provided in this embodiment 2 comprises the following steps: Step S1, ultrasonically clean the anode glass substrate coated with indium tin oxide (ITO) with detergent, distilled water, acetone, and ethanol for 3 times, each time for 15 minutes. After cleaning, blow dry the glass substrate and treat it in an ultraviolet ozone device for 15 minutes to obtain a pretreated substrate wafer.

[0053] Step S2: spin-coat the PTAA solution on the pretreated glass substrate, heat it at 100° C. for 10 min for annealing, and then naturally cool it to room temperature to form a hole transport layer.

[0054] Step S3, MAI and PbI2 were dissolved in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) solution at a molar ratio of 1:1.2, and stirred at room temperature for 12 h to obtain a perovskite precursor solution (MAPbI3). The perovskite precursor solution was spin-coated on the hole transport layer at a speed of 4000 rpm, and then the anti-solvent chlorobenzene solution was quickly added at the 5th second of rotation, and the dripping was completed within 2 seconds, which can promote the rapid crystallization of the perovskite layer. After annealing at 100°C for 10 minutes, a perovskite layer, i.e., an active layer, was obtained with a thickness of 300 nm.

[0055] Step S4: spin-coat the electron transport layer solution on the perovskite layer to form an organic electron transport layer, and the rotation speed of the electron transport layer spin coating is 2000 rpm. The specific steps of preparing the organic electron transport layer include: Step s41, dissolving a certain amount of CY4 in chlorobenzene to form a solution, stirring for 12 hours to form a CY4 solution, wherein the concentration of the CY4 solution is 1 mg / mL.

[0056] Step s42, mixing the CY4 solution into the PCBM solution in a certain proportion, stirring for 12 hours, and filtering with a filter head before use to form a PCBM:CY4 solution, wherein the concentration of the PCBM:CY4 solution is 0.01 mg / mL.

[0057] Step s43, spin-coating the PCBM:CY4 solution on a coating machine for 30 seconds, and forming an organic electron transport layer, namely, a PCBM:CY4 film, after curing.

[0058] Step S5, spin coating the BCP solution on the organic electron transport layer to obtain a cathode modification layer.

[0059] Step S6: depositing cathode material Ag onto the cathode modification layer by thermal evaporation under vacuum.

[0060] The structure of the perovskite solar cell device obtained in Example 2 provided by the present invention is ITO / PTAA / MAPbl3 / PCBM:CY4 / BCP / Ag. The performance of the perovskite solar cell device was tested. Under the optimal conditions, at 100 mW / cm 2 Under simulated sunlight, the open circuit voltage is 1.06 V and the short circuit current is 22.46 mA / cm 2 , the filling factor is 79.16% and the photoelectric conversion efficiency is 18.85%. Example 3

[0061] The method for preparing a perovskite solar cell doped with an organic electron transport layer provided in this embodiment 3 comprises the following steps: Step S1, ultrasonically clean the anode glass substrate coated with indium tin oxide (ITO) with detergent, distilled water, acetone, and ethanol for 3 times, each time for 15 minutes. After cleaning, blow dry the glass substrate and treat it in an ultraviolet ozone device for 15 minutes to obtain a pretreated substrate wafer.

[0062] Step S2: spin-coat the PTAA solution on the pretreated glass substrate, heat it at 100° C. for 10 min for annealing, and then naturally cool it to room temperature to form a hole transport layer.

[0063] Step S3, MAI and PbI2 were dissolved in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) solution at a molar ratio of 1:1.2, and stirred at room temperature for 12 h to obtain a perovskite precursor solution (MAPbI3). The perovskite precursor solution was spin-coated on the hole transport layer at a speed of 4000 rpm, and then the anti-solvent chlorobenzene solution was quickly added at the 5th second of rotation, and the dripping was completed within 2 seconds, which can promote the rapid crystallization of the perovskite layer. After annealing at 100°C for 10 minutes, a perovskite layer, i.e., an active layer, was obtained with a thickness of 300 nm.

[0064] Step S4: spin-coat the electron transport layer solution on the perovskite layer to form an organic electron transport layer, and the rotation speed of the electron transport layer spin coating is 2000 rpm. The specific steps of preparing the organic electron transport layer include: Step s41, dissolving a certain amount of CY4 in chlorobenzene to form a solution, stirring for 12 hours to form a CY4 solution, wherein the concentration of the CY4 solution is 1 mg / mL.

[0065] Step s42, mixing the CY4 solution into the PCBM solution in a certain proportion, stirring for 12 hours, and filtering with a filter head before use to form a PCBM:CY4 solution, wherein the concentration of the PCBM:CY4 solution is 0.04 mg / mL.

[0066] Step s43, spin-coating the PCBM:CY4 solution on a coating machine for 30 seconds, and forming an organic electron transport layer, namely, a PCBM:CY4 film, after curing.

[0067] Step S5: spin-coating the BCP solution on the organic electron transport layer to obtain a cathode modification layer.

[0068] Step S6: depositing cathode material Ag onto the cathode modification layer by thermal evaporation under vacuum.

[0069] The structure of the perovskite solar cell device obtained in Example 3 provided by the present invention is ITO / PTAA / MAPbl3 / PCBM:CY4 / BCP / Ag. The performance of the perovskite solar cell device was tested. Under the optimal conditions, at 100 mW / cm 2 Under simulated sunlight, the open circuit voltage is 1.05 V and the short circuit current is 22.38 mA / cm 2 , the filling factor is 77.87% and the photoelectric conversion efficiency is 18.30%. Example 4

[0070] The method for preparing a perovskite solar cell doped with an organic electron transport layer provided in this embodiment 4 comprises the following steps: Step S1, ultrasonically clean the anode glass substrate coated with indium tin oxide (ITO) with detergent, distilled water, acetone, and ethanol for 3 times, each time for 15 minutes. After cleaning, blow dry the glass substrate and treat it in an ultraviolet ozone device for 15 minutes to obtain a pretreated substrate wafer.

[0071] Step S2: spin-coat the PTAA solution on the pretreated glass substrate, heat it at 100° C. for 10 min for annealing, and then naturally cool it to room temperature to form a hole transport layer.

[0072] Step S3, MAI and PbI2 were dissolved in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) solution at a molar ratio of 1:1.2, and stirred at room temperature for 12 h to obtain a perovskite precursor solution (MAPbI3). The perovskite precursor solution was spin-coated on the hole transport layer at a speed of 4000 rpm, and then the anti-solvent chlorobenzene solution was quickly added at the 5th second of rotation, and the dripping was completed within 2 seconds, which can promote the rapid crystallization of the perovskite layer. After annealing at 100°C for 10 minutes, a perovskite layer, i.e., an active layer, was obtained with a thickness of 300 nm.

[0073] Step S4: spin-coat the electron transport layer solution on the perovskite layer to form an organic electron transport layer, and the rotation speed of the electron transport layer spin coating is 2000 rpm. The specific steps of preparing the organic electron transport layer include: Step s41, dissolving a certain amount of CY4 in chlorobenzene to form a solution, stirring for 12 hours to form a CY4 solution, wherein the concentration of the CY4 solution is 1 mg / mL.

[0074] Step s42, mixing the CY4 solution into the PCBM solution in a certain proportion, stirring for 12 hours, and filtering with a filter head before use to form a PCBM:CY4 solution, wherein the concentration of the PCBM:CY4 solution is 0.06 mg / mL.

[0075] Step s43, spin-coating the PCBM:CY4 solution on a coating machine for 30 seconds, and forming an organic electron transport layer, namely, a PCBM:CY4 film, after curing.

[0076] Step S5, spin coating the BCP solution on the organic electron transport layer to obtain a cathode modification layer.

[0077] Step S6: depositing cathode material Ag onto the cathode modification layer by thermal evaporation under vacuum.

[0078] The structure of the perovskite solar cell device obtained in Example 4 provided by the present invention is ITO / PTAA / MAPbl3 / PCBM:CY4 / BCP / Ag. The performance of the perovskite solar cell device was tested. Under the optimal conditions, at 100 mW / cm 2 Under simulated sunlight, the open circuit voltage is 1.04 V and the short circuit current is 21.07 mA / cm 2 , the filling factor is 75.17% and the photoelectric conversion efficiency is 16.47%. Example 5

[0079] The difference between this embodiment 5 and embodiment 1 is that in step S4, an organic electron transport layer is formed, the rotation speed of the electron transport layer during spin coating is 2000 rpm, and the concentration of the PCBM:CY4 solution is 0.1 mg / ml. Other steps and methods are the same as those in embodiment 1.

[0080] The structure of the perovskite solar cell device obtained in Example 5 provided by the present invention is ITO / PTAA / MAPbl3 / PCBM:CY4 / BCP / Ag. The performance of the perovskite solar cell device was tested. Under the optimal conditions, at 100 mW / cm 2 Under simulated sunlight, the open circuit voltage is 1.01 V and the short circuit current is 20.04 mA / cm 2 , the filling factor is 70.81% and the photoelectric conversion efficiency is 14.33%. Comparative Example 1

[0081] The difference between this comparative example 1 and the embodiment 1 is that in step S4, the organic electron transport layer uses a single PCBM solution. The other steps and methods are the same as those in the embodiment 1 and will not be described in detail here.

[0082] The structure of the perovskite solar cell device prepared in this comparative example 1 is ITO / PTAA / MAPbl3 / PCBM / BCP / Ag. The performance of the perovskite solar cell in this comparative example 1 is tested at 100 mW / cm 2 Under simulated sunlight, the open circuit voltage is 1.03 V and the short circuit current is 21.59 mA / cm 2 , the filling factor is 77.06% and the photoelectric conversion efficiency is 17.20%.

[0083] The photoelectric conversion efficiency of the perovskite solar cell prepared in this comparative example 1 is low because there are defects in the organic electron transport layer, and these defects provide channels for water and oxygen to corrode the active layer; and due to the nature of PCBM itself, it is easy to aggregate, so the coverage with the perovskite layer is poor, thereby reducing the photoelectric conversion efficiency of the perovskite cell.

[0084] Figure 5 The fluorescence spectra of the perovskite layer film + electron transport layer film prepared in Example 1 of the present invention and in Comparative Example 1 are as follows. The fluorescence spectrum of the perovskite layer film + electron transport layer film (PCBM:CY4) prepared in Example 1 is Figure 5 The dotted line in the figure shows that the fluorescence spectrum of the perovskite layer film + electron transport layer film (PCBM) prepared in comparative example 1 is Figure 5 The solid line in .

[0085] like Figure 6 The UV absorption spectra of the organic electron transport layer thin films prepared in Example 1 and Comparative Example 1 of the present invention are shown. Among them, the UV absorption spectra of the organic electron transport layer thin films prepared in Example 1 are Figure 6 The dotted line in the figure shows that the ultraviolet absorption spectrum of the organic electron transport layer film prepared in Comparative Example 1 is Figure 6 The solid line in .

[0086] It can be seen from the figure that neither the organic electron transport layer film of Example 1 nor the organic electron transport layer film of Comparative Example 1 affects the light absorption of the perovskite layer, and when the CY4 doping concentration is 0.02 mg / mL, the spectral intensity is slightly higher than that of the samples prepared in the other embodiments. Therefore, when the CY4 doping concentration is 0.02 mg / mL, the perovskite solar cell can obtain the best photovoltaic parameters and performance.

[0087] Figure 7 The scanning electron microscopic image of the cross section of the perovskite film and the perovskite solar cell prepared in Example 1 of the present invention. Figure 7 The left picture in the figure is a scanning electron microscopy image of the surface of the perovskite film. Figure 7 The right image in the figure is a scanning electron micrograph of a cross-section of a perovskite solar cell device.

[0088] Figure 8 The current density-voltage characteristic curves of the perovskite solar cells prepared in Example 1 of the present invention and in Comparative Example 1 are shown in FIG. The current density-voltage characteristic curves of the perovskite solar cells prepared in Example 1 are shown in FIG. Figure 8 The hollow dotted line in the figure shows the current density-voltage characteristic curve of the perovskite solar cell prepared in Comparative Example 1. Figure 8 The solid dot line in .

[0089] Fig. 9 The contact angles of the PCBM:CY4 films prepared in Example 1 and Comparative Example 1 of the present invention are shown in the figure on the left. The contact angle of the PCBM film prepared in Comparative Example 1 is shown in the figure on the right. The contact angle of the PCBM:CY4 film prepared in Example 1 is shown in the figure on the right. As can be seen from the figure, after doping with CY4, the contact angle is the largest, indicating that the hydrophobicity is the best, which can well prevent external moisture from corroding the perovskite layer, thereby improving the photoelectric performance of the perovskite solar cell device.

[0090] In summary: the perovskite solar cell doped with an organic electron transport layer provided by the present invention, the perovskite solar cell structure includes from bottom to top: a substrate, an anode, a hole transport layer, a perovskite layer, an organic electron transport layer, a cathode modification layer and a cathode. Among them, the organic electron transport layer is prepared by doping CY4 as a dopant into a chlorobenzene solution of PCBM. The organic electron transport layer of the present invention can well reduce carrier recombination, improve interface level contact, and improve the electron transport layer's performance in extracting and transporting electrons. The photoelectric conversion efficiency of the perovskite solar cell prepared by this method reaches 19.80%, which improves the photoelectric performance of the perovskite solar cell.

[0091] At the same time, the present invention utilizes a novel dopant CY4 to dope a traditional electron transport layer, and the obtained solution can be directly spin-coated on the perovskite layer without the need for annealing treatment, and the operation is simple, thereby improving the performance and stability of the perovskite solar cell device; at the same time, the cost is low and it is readily available, and the preparation of large-area thin films can be realized.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing an organic electron transport layer, characterized in that: The preparation method comprises the following steps: Step 1, dissolving the dopant CY4 in a chlorobenzene (CB) solvent, stirring and filtering to form a CY4 precursor solution; Step 2, doping the CY4 precursor solution into the PCBM solution, stirring and filtering to form a PCBM:CY4 solution; Step 3, spin coating the PCBM:CY4 solution onto a substrate, and obtaining an organic electron transport layer after curing.

2. The method for preparing an organic electron transport layer according to claim 1, characterized in that: The concentration of the CY4 precursor solution is 1 mg / mL.

3. The method for preparing an organic electron transport layer according to claim 1, characterized in that: In the step 1, the stirring time is 12 hours; in the step 2, the stirring time is 12 hours.

4. The method for preparing an organic electron transport layer according to claim 1, characterized in that: The concentration of the PCBM:CY4 solution is 0.01-0.1 mg / mL.

5. A method for preparing a perovskite solar cell, characterized in that: The preparation method comprises the following steps: Step S1, ultrasonically clean the glass substrate coated with the anode material, and treat it with an ultraviolet ozone machine to obtain a pretreated substrate substrate; Step S2, spin coating the PTAA solution on the substrate, heating at 100° C. for 10 min for annealing, and then naturally cooling to room temperature to obtain a hole transport layer; Step S3, transferring the substrate obtained in step S2 into a glove box, and spin-coating the perovskite precursor solution on the hole transport layer using a one-step anti-solvent method, heating at 100° C. for 10 min for annealing treatment to obtain a perovskite layer; Step S4, spin coating the PCBM:CY4 solution on the perovskite layer to obtain an organic electron transport layer; Step S5, spin coating the BCP solution on the organic electron transport layer to obtain a cathode modification layer; Step S6, depositing the cathode material onto the cathode modification layer by thermal evaporation under vacuum; Wherein, the organic electron transport layer is prepared by the method for preparing an organic electron transport layer according to claims 1-4.

6. The method for preparing a perovskite solar cell according to claim 5, characterized in that: In step S3, the perovskite precursor solution is prepared by the following method: Dissolving donor A and donor B in an organic solvent, and stirring evenly to obtain the perovskite precursor solution; Wherein, the donor A is methylammonium iodide, the donor B is lead iodide, and the organic solvent is N,N-dimethylformamide and dimethyl sulfoxide.

7. The method for preparing a perovskite solar cell according to claim 6, characterized in that: The molar ratio of the donor A to the donor B is 1:(1-2).

8. The method for preparing a perovskite solar cell according to claim 6, characterized in that: The total mass percentage of the donor A and the donor B in the perovskite precursor solution is 35-50 wt %.

9. The method for preparing a perovskite solar cell according to claim 5, characterized in that: In the step S5, the BCP solution is spin-coated using a coating machine, the spin-coating time is 30 seconds, and the spin-coating speed is 4000 rpm.

10. A perovskite solar cell, characterized in that: The perovskite solar cell is prepared by the preparation method according to any one of claims 5 to 9.

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