Thin film optimization preparation method for perovskite laminated solar cell

Abstract

The invention discloses an optimized preparation method for a perovskite laminated solar cell film. The optimized preparation method is especially suitable for cost reduction and efficiency improvement of a ternary A-bit perovskite laminated solar cell. The technical key point is that guanidine iodide (GAI) is introduced into a perovskite precursor solution, so that the photoelectric property and the stability of the perovskite solar cell are remarkably improved. In the preparation process of the thin film, a toluene solution containing tri-n-octylphosphine oxide (TOPO) is adopted, so that the photoluminescence intensity of a sample is effectively enhanced. Furthermore, a layer of toluene solution containing polystyrene is spin-coated on the spin-coated and annealed thin film, so that the long-term stability of the thin film is greatly improved. According to the method, the photoelectric conversion efficiency and the stability of the perovskite laminated solar cell are remarkably improved.

Description

Technical Field

[0001] The invention relates to the field of preparation of high-efficiency thin-film photovoltaic materials, in particular to a method for preparing a thin film for a perovskite stacked solar cell. Background Art

[0002] In the current field of solar cell technology, tandem solar cells have attracted widespread attention because they can more effectively utilize the solar spectrum and thus improve energy conversion efficiency. The top absorption layer is a key component of tandem solar cells. This layer usually needs to have a wide band gap to achieve absorption of higher energy photons. However, some materials in the prior art have limitations in photoluminescence intensity, which limits the overall performance of solar cells. In order to enhance the photoluminescence intensity, researchers have tried a variety of processing techniques, including but not limited to doping, post-processing, etc. These post-processing techniques can improve the photoluminescence intensity of materials to a certain extent, thereby improving the photoelectric conversion efficiency of solar cells. Although these technologies have achieved certain results, they are usually accompanied by complex process flows and may have an adverse effect on the stability and crystallinity of the materials. In addition, some processing costs are high, which is not conducive to large-scale production. Therefore, it is necessary to propose a simple, efficient and low-cost preparation method to effectively improve the photoluminescence intensity and photovoltaic performance of perovskite films without compromising the stability of the materials. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a simple and efficient preparation method to significantly improve the photoluminescence intensity and photovoltaic performance of perovskite films while ensuring that the stability of the material is not impaired; in addition, another purpose of the present invention is to reduce the complexity and cost of the preparation process to meet the needs of large-scale production, thereby overcoming the limitations of the prior art.

[0004] Technical solution: In order to achieve the above-mentioned invention object, the present invention provides a thin film optimization preparation method for perovskite tandem solar cells, which comprises the following steps:

[0005] 1. Add guanidine iodide (GAI) to the ternary A-site (Cs / FA / MA) perovskite precursor solution, where GA + , Cs + , FA + and MA + The concentration ratio of GA + :Cs + :FA + :MA + =1.5n:0.075(1-n):0.32775(1-n):1.09725(1-n), the value of n ranges from 0 to 0.12, heated and stirred in a nitrogen environment at 50 to 70°C overnight;

[0006] 2. The perovskite film is prepared by a two-step spin coating method. The first step is to spin-coat the perovskite precursor solution, and the second step is to spin-coat a toluene antisolvent containing 0.8 to 1.2 mmol / mL TOPO. After adding TOPO to toluene, it is necessary to stir at room temperature for at least 60 minutes until TOPO is completely dissolved.

[0007] 3. After the spin coating operation is completed, the substrate is placed on a hot plate for annealing at a temperature of 120 to 140°C for 60 to 75 minutes;

[0008] 4. After the annealing treatment is completed, continue to spin-coat 100 μL of a toluene solution containing 0.1 to 0.2 g / mL polystyrene. After adding polystyrene to the toluene solution, heat and stir at 60 to 80° C. for 2 to 3 hours until the polystyrene is completely dissolved;

[0009] 5. After the spin coating operation is completed, the substrate is placed on a hot plate for annealing at a temperature of 60 to 80°C for 60 to 75 minutes.

[0010] In step 2, the first step of spin coating has a time of 10 seconds and a spin coating speed of 1000 rpm, the second step of spin coating has a time of 20 seconds and a spin coating speed of 5000 to 7000 rpm, the above-mentioned precursor solution is added to the substrate before the first step of spin coating, and the above-mentioned toluene solution is added 10 seconds after the start of the second step of spin coating.

[0011] The spin coating speed of the toluene solution containing polystyrene in step 4 is 5000 to 7000 rpm, and the spin coating time is 10 seconds.

[0012] Beneficial effects: The thin film optimization preparation method for perovskite tandem solar cells provided by the present invention has the following significant advantages compared with the prior art:

[0013] (1) The method of the present invention is simple to operate, has low dependence on equipment, and has a short preparation cycle, which is easy to implement and promote;

[0014] (2) The perovskite film prepared by the method of the present invention has good crystallinity, which is beneficial to improving the photovoltaic performance of the film;

[0015] (3) By doping and post-treatment in the perovskite precursor solution, the fluorescence intensity of the prepared perovskite composite film is significantly improved compared with the initial film, which is beneficial to improve the photovoltaic performance;

[0016] (4) Adding polystyrene can isolate moisture and oxygen in the environment, which is beneficial to improving the long-term service life of solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1The scanning electron microscope (SEM) spectra after adding different amounts of GAI to the Cs / FA / MA solution in the example are used to intuitively demonstrate the effect of GAI content on the microstructure of the perovskite film;

[0018] Figure 2 The peak position spectrum of lead (Pb) in the X-ray photoelectron spectroscopy (XPS) after adding different amounts of GAI to the Cs / FA / MA solution in the embodiment is used to analyze the effect of the change of GAI content on the chemical state of the perovskite film;

[0019] Figure 3 The X-ray diffraction (XRD) diagram after adding different amounts of GAI to the Cs / FA / MA solution in the embodiment is used to characterize the effect of GAI content on the crystal structure of the perovskite film;

[0020] Figure 4 The absorption spectrum and fluorescence spectrum of the perovskite film prepared by spin coating and annealing process after adding TOPO to the toluene solution in the example are used to evaluate the effect of TOPO on the optical properties of the perovskite film. DETAILED DESCRIPTION

[0021] The present invention will be further explained below in conjunction with the embodiments and accompanying drawings:

[0022] 1. Preparation of perovskite precursor solution: Weigh an appropriate amount of GAI and dissolve it in a mixed solution of anhydrous dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a concentration of 1.5 mmol / mL, and the volume ratio of DMF to DMSO is 7:3. Stir until GAI is completely dissolved to obtain a GAI solution; weigh an appropriate amount of MAI, FAI, CsI, PbI2 and PbBr2 and dissolve them in an anhydrous DMF:DMSO mixed solution of the same proportion, with concentrations of 1.097, 0.328, 0.075, 0.91 and 0.34 mmol / mL, respectively. Stir until all solids are completely dissolved to obtain a Cs / FA / MA solution; filter the above two groups of solutions through a 0.45 mm polytetrafluoroethylene (PTFE) filter, and then heat them on a hot plate at 60 ° C for 2 hours; mix the GAI solution and the Cs / FA / MA solution according to the GAI ratio. + and (Cs + +FA + +MA + ) with a molar concentration ratio of: n / (1-n), where n is 0, 0.03, 0.06, and 0.12;

[0023] 2. Pipette 100 μL of the mixed solution onto the substrate, first spin-coat at 1000 rpm for 10 seconds, then increase the speed to 5000 rpm and continue spin-coating for 20 seconds;

[0024] 3. Dissolve TOPO in a toluene solution at a concentration of 1 mmol / mL and stir at room temperature for 60 minutes until TOPO is completely dissolved; 10 seconds after the second spin coating in step 2, drop 100 μL of the toluene solution;

[0025] 4. After the spin coating operation is completed, the substrate is immediately transferred to a hot plate at 125°C for annealing for 1 hour;

[0026] 5. Dissolve polystyrene in toluene at a concentration of 0.15 g / mL, and then heat and stir at 70°C for 3 hours; after the annealing process in step 4 is completed, drop 100 μL of the toluene solution containing polystyrene onto the film layer, and spin coat at a speed of 5000 rpm for 10 seconds;

[0027] 6. The final prepared samples were subjected to the following characterization steps: microscopic morphology analysis was performed using SEM; chemical composition and electronic state analysis was performed using XPS; crystal structure analysis was performed using XRD technology; UV-visible absorption spectroscopy and steady-state photoluminescence spectroscopy were performed to test the light absorption characteristics and photoluminescence performance of the samples.

[0028] Figure 1 The SEM spectra after adding different amounts of GAI to the perovskite precursor solution show that when n = 0.03, that is, Figure 1 b), the most densely packed particles indicate the highest crystallinity of the material, with the largest proportion of crystals in the material and the least non-crystalline or amorphous regions, forming a more tightly packed crystal structure;

[0029] Figure 2 The changes in the Pb peak position in XPS after adding different amounts of GAI to the perovskite precursor solution are shown. It can be concluded that when n = 0.03, the binding energy of Pb is the strongest, which means that the chemical state of the Pb atom is more stable and the interaction between the Pb atom and the surrounding atoms is stronger;

[0030] Figure 3 The peak position changes of XRD after adding different amounts of GAI to the perovskite precursor solution are shown. It can be concluded that when n = 0.03, the diffraction peak angle θ is the largest, and the optimal crystal structure configuration is achieved. According to the Bragg formula nλ = 2dsinθ, the lattice spacing d is the smallest at this time, which is consistent with the phenomenon observed in SEM that the particles are the densest when n = 0.03;

[0031] Figure 4 The absorption spectrum a) and fluorescence spectrum b) of the perovskite film after adding TOPO to the toluene solution indicate that the introduction of TOPO greatly increases the photoluminescence intensity of the material and also causes the absorption peak to blue-shift.

[0032] In this embodiment, the introduction of GAI can improve the crystallinity of the material and the density of the crystal structure, enhance the chemical stability of the Pb atoms in the material and their interaction with the surrounding atoms, and optimize the crystal structure configuration of the material to achieve a better crystal structure. The introduction of TOPO can significantly enhance the photoluminescence intensity of the material and improve the optical properties.

[0033] The above is only a preferred embodiment of the present invention. However, for those skilled in the art, there are many possible improvements and adjustments without departing from the basic principles of the present invention. These potential improvements and adjustments should also be considered to be included in the protection scope of the present invention.

Claims

1. A thin film optimization preparation method for perovskite tandem solar cells, characterized in that: (1) adding guanidine iodide (GAI) to the ternary A-site (Cs / FA / MA) perovskite precursor solution and heating and stirring overnight in a nitrogen environment; (2) preparing the perovskite film by a two-step spin coating method, wherein the first step is to spin-coat the perovskite precursor solution, and the second step is to spin-coat a toluene antisolvent containing tri-n-octylphosphine oxide (TOPO); (3) After annealing the spin-coated film, a toluene solution containing polystyrene is spin-coated again.

2. The preparation method according to claim 1, further characterized in that: (1) GA in the solution after adding GAI + , Cs + , FA + and MA + The concentration ratio of GA + :Cs + :FA + :MA + =1.5n:0.075(1-n):0.32775(1-n):1.09725(1-n), the value range of n is 0 to 0.12, and the temperature of heating and stirring is 50 to 70°C; (2) the concentration of TOPO in toluene antisolvent is 0.8 to 1.2 mmol / mL, and the mixture is stirred at room temperature for at least 60 minutes until TOPO is completely dissolved; (3) The concentration of polystyrene in toluene solution is 0.1 to 0.2 g / mL, and the solution is heated and stirred at 60 to 80° C. for 2 to 3 hours until the polystyrene is completely dissolved.

3. The preparation method according to claim 1, wherein the spin coating and annealing process are specifically as follows: (1) Spin coating a perovskite precursor solution containing GAI and a toluene solution containing TOPO, wherein the first step of spin coating has a time of 10 seconds and a spin coating speed of 1000 rpm, and the second step of spin coating has a time of 20 seconds and a spin coating speed of 5000 to 7000 rpm, wherein the above-mentioned precursor solution is added before the first step of spin coating, and the above-mentioned toluene solution is added 10 seconds after the start of the second step of spin coating; (2) After the spin coating operation is completed, the substrate is placed on a hot plate for annealing at a temperature of 120 to 140° C. for a time of 60 to 75 minutes; (3) After the annealing treatment is completed, 100 μL of the above-mentioned toluene solution containing polystyrene is spin-coated on the perovskite film at a rotation speed of 5000 to 7000 rpm for 10 seconds. After the spin coating operation is completed, the substrate is placed on a hot plate for annealing at a temperature of 60 to 80° C. for 60 to 75 minutes.

Images