Preparation method and application of all-inorganic tin-lead perovskite thin film

Abstract

The invention discloses a preparation method and application of an all-inorganic tin-lead perovskite thin film, and the preparation method comprises the steps: modifying a conductive glass layer through a hole transport layer, coating the hole transport layer with a perovskite precursor solution, and carrying out the annealing treatment to form an all-inorganic tin-lead perovskite thin film, namely, a 4-hydrazinobenzoic acid doped CsPb0. 5Sn0. 5I3 polycrystalline thin film. The molar ratio of the doped 4-hydrazinobenzoic acid is 0.82 to 5.74 percent. The 4-hydrazinobenzoic acid can effectively inhibit the oxidation process from Sn < 2 + > to Sn < 4 + >, prevent divalent tin from being oxidized, reduce the deep energy level defect state density in the film, selectively and preferentially affine Sn, and delay the crystallization kinetics process of an Sn-I framework by regulating and controlling the complexing strength of Sn-based components in a perovskite precursor solution. The full-inorganic tin-lead perovskite thin film is uniform in grain size, few in grain boundary defect and preferred in orientation, and the photoelectric conversion efficiency and the stability of a solar cell are obviously improved.

Description

Technical Field

[0001] The present invention relates to the field of solar cells, and in particular to a preparation method and application of an all-inorganic tin-lead perovskite thin film. Background Art

[0002] Perovskite solar cells have become a research hotspot in the photovoltaic field due to their excellent photoelectric performance and low cost. Among them, trans (pin) structure perovskite solar cells have attracted much attention due to their advantages such as simple preparation process, strong low-temperature compatibility and high compatibility with stacked cell integration. Traditional trans perovskite solar cells mostly use organic-inorganic hybrid perovskite materials (such as MAPbI3 or FAPbI3), but their thermal stability issues seriously restrict their practical applications. Studies have shown that organic cations (such as MA + , FA + ) are prone to decomposition under high temperature or light conditions, leading to lattice distortion and performance degradation. Therefore, replacing organic components with all-inorganic perovskite materials (such as CsPbX3) has become an important research direction for improving the thermal stability of devices.

[0003] The research on all-inorganic inverse perovskite of tin-lead (Sn-Pb) mixed system is more challenging. Although the introduction of Sn can reduce the band gap (1.2-1.4 eV), broaden the light absorption range and adapt to the design of tandem cells, the 2+ Easily oxidized to Sn 4+ The characteristics of Sn-Pb alloy perovskite significantly increase the defect density of the film, and the crystallization dynamics of Sn-Pb alloy perovskite are more difficult to control. In addition, the energy level matching problem at the interface between Sn-Pb perovskite and the transport layer in the trans structure is more complicated, and traditional passivators or interface modification materials may fail due to insufficient chemical compatibility. The photoelectric conversion efficiency of untreated all-inorganic Sn-Pb system trans devices reported in existing literature is generally less than 10%. It is now necessary to develop a synergistic optimization strategy that combines defect passivation, energy level matching and phase stability improvement. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a 4-hydrazinobenzoic acid-doped all-inorganic tin-lead perovskite (CsPb 0.5 Sn 0.5 I3) Preparation method and application of thin film, the CsPb 0.5 Sn 0.5 I3 polycrystalline thin film has a significant effect on improving the photoelectric conversion efficiency and stability of solar cells.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a method for preparing an all-inorganic tin-lead perovskite film, wherein the conductive glass layer is cleaned and dried, and then modified with a hole transport layer, a perovskite precursor liquid is coated on the hole transport layer, and an all-inorganic tin-lead perovskite film is formed after annealing. The all-inorganic tin-lead perovskite film is CsPb doped with 4-hydrazinobenzoic acid. 0.5 Sn 0.5 I3 polycrystalline film, the molar ratio of the 4-hydrazinobenzoic acid doped in the all-inorganic tin-lead perovskite film is 0.82-5.74%.

[0006] The all-inorganic tin-lead perovskite film prepared by the method of the present invention is CsPb doped with 4-hydrazinobenzoic acid. 0.5 Sn 0.5 I3 polycrystalline film. 4-Hydrazinobenzoic acid (HBA) has hydrazine and carboxyl groups. On the one hand, the reducing hydrazine group can transfer to Sn through its electron-rich properties. 2+ Provide electron pairs to effectively suppress Sn 2+ To Sn 4+ The oxidation process of divalent tin is prevented, and the density of deep energy level defect states in the film is reduced; on the other hand, the carboxyl group can coordinate with Sn by virtue of its dynamic coordination ability. 2+ The formation of selective chelation can selectively preferentially bind to Sn, and by regulating the complex strength of the Sn-based components in the perovskite precursor solution, the crystallization kinetics of the Sn-I skeleton can be delayed. This differentiated crystallization regulation mechanism enables the Sn-Pb bimetallic system to achieve a dynamic balance of the crystallization rates of the Sn-based and Pb-based components during the film growth process, inhibiting the Pb 2+ With Sn 2+ The phase separation tendency of CsPb 0.5 Sn 0.5 The crystallization quality of I3 was improved, the surface morphology of the film was improved, and finally HBA-doped CsPb with uniform grain size, few grain boundary defects and preferred orientation was obtained. 0.5 Sn 0.5 I3 polycrystalline thin film, the CsPb 0.5 Sn 0.5 I3 polycrystalline thin film has a significant effect on improving the photoelectric conversion efficiency and stability of solar cells.

[0007] Preferably, the perovskite precursor solution is formed by mixing CsI, PbI2, SnI2, SnF2, 4-hydrazinobenzoic acid and a solvent, wherein the concentration ratio of CsI, PbI2, SnI2 and SnF2 in the perovskite precursor solution is 1:0.5:0.5:0.05, the concentration of 4-hydrazinobenzoic acid is 1-7 mg / mL, and the solvent is at least one of DMF and DMSO.

[0008] As a further preference, in the perovskite precursor solution, the concentration of CsI is 0.6-1 mol / L, the concentration of PbI2 is 0.3-0.5 mol / L, the concentration of SnI2 is 0.3-0.5 mol / L, and the concentration of SnF2 is 0.03-0.05 mol / L.

[0009] As a specific preferred embodiment, in the perovskite precursor solution, the concentration of CsI is 0.8 mol / L, the concentration of PbI2 is 0.4 mol / L, the concentration of SnI2 is 0.4 mol / L, the concentration of SnF2 is 0.04 mol / L, and the concentration of 4-hydrazinobenzoic acid is 3 mg / mL.

[0010] As further preferred, the solvent is DMF and DMSO, and the volume ratio of DMF to DMSO is 3:1.

[0011] As a further preference, the preparation process of the perovskite precursor solution is: first, CsI, PbI2, SnI2 and SnF2 are dissolved in a solvent, stirred at room temperature for 3 h, then 4-hydrazinobenzoic acid is added, and then shaken to uniformly disperse 4-hydrazinobenzoic acid in the solvent.

[0012] Preferably, the annealing treatment is a two-stage annealing treatment, first annealing at 70-90°C for 1-2 minutes, and then annealing at 100-115°C for 4-6 minutes.

[0013] Preferably, the hole transport layer is made of PEDOT:PSS.

[0014] As a further preference, the preparation process of the hole transport layer is: diluting PEDOT:PSS with 3 times the volume of deionized water to obtain a PEDOT:PSS solution, spin-coating the PEDOT:PSS solution onto the conductive glass layer at a speed of 4000 rpm for 30 s, and then annealing at 120-180 ° C for 15-20 min.

[0015] Application of the above-mentioned all-inorganic tin-lead perovskite film in solar cells.

[0016] Compared with the prior art, the present invention has the following advantages: the all-inorganic tin-lead perovskite film prepared by the method for preparing the all-inorganic tin-lead perovskite film is CsPb doped with 4-hydrazinobenzoic acid. 0.5 Sn 0.5 I3 polycrystalline film. 4-Hydrazinobenzoic acid can effectively inhibit Sn 2+ To Sn 4+The oxidation process of Sn-I is slowed down, preventing the oxidation of divalent tin, reducing the density of deep-level defect states in the film, and selectively preferentially affinitizing Sn. By regulating the complexation strength of Sn-based components in the perovskite precursor solution, the crystallization kinetics of the Sn-I skeleton is delayed. This differentiated crystallization regulation mechanism promotes the dynamic balance of the crystallization rates of Sn-based and Pb-based components in the Sn-Pb bimetallic system during the film growth process, inhibiting the Pb 2+ With Sn 2+ The phase separation tendency of CsPb 0.5 Sn 0.5 The all-inorganic tin-lead perovskite film of the present invention has uniform grain size, few grain boundary defects and preferred orientation, which significantly improves the photoelectric conversion efficiency and stability of solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 CsPb of Example 2 0.5 Sn 0.5 SEM image of the surface of I3 polycrystalline film; Figure 2 CsPb of Comparative Example 1 0.5 Sn 0.5 SEM image of the surface of I3 polycrystalline film; Figure 3 CsPb of Example 2 0.5 Sn 0.5 Grain size distribution histogram of I3 polycrystalline film; Figure 4 CsPb of Comparative Example 1 0.5 Sn 0.5 Grain size distribution histogram of I3 polycrystalline film; Figure 5 CsPb of Example 2 0.5 Sn 0.5 AFM image of I3 polycrystalline film; Figure 6 CsPb of Comparative Example 1 0.5 Sn 0.5 AFM image of I3 polycrystalline thin film; Figure 7 The CsPb of Example 2 and Comparative Example 1 0.5 Sn 0.5 XRD pattern of I3 polycrystalline thin film; Figure 8 The CsPb of Example 2 and Comparative Example 1 0.5 Sn 0.5 XPS pattern of I3 polycrystalline thin film; Figure 9 The CsPb of Example 2 and Comparative Example 10.5 Sn 0.5 Comparison pictures of I3 polycrystalline thin films gradually decomposing in air; Figure 10 For the CsPb of Example 2 and Comparative Example 1 0.5 Sn 0.5 I3 JV curve of solar cells made of polycrystalline thin films; Note: Figures 1-10 In the table, “w / o HBA” means no HBA is added, and “with HBA” means HBA is added. DETAILED DESCRIPTION

[0018] The following is an explanation and description of the technical solutions of the present invention in conjunction with the embodiments of the accompanying drawings, but the following embodiments are only preferred embodiments of the present invention and are not exhaustive. Based on the embodiments in the implementation manner, other embodiments obtained by those skilled in the art without making any creative work are all within the scope of protection of the present invention.

[0019] The method for preparing the all-inorganic tin-lead perovskite thin film of Example 1 comprises the following steps: Step S1: Prepare a piece of conductive glass (ITO) with a size of 1.5 cm × 1.5 cm as the conductive glass layer, clean and dry it; Step S2: PEDOT:PSS was diluted with 3 times the volume of deionized water to form a PEDOT:PSS solution, and the PEDOT:PSS solution was spin-coated onto the conductive glass layer at a speed of 4000 rpm for 30 seconds, followed by annealing at 150°C for 15-20 minutes to form a hole transport layer; Step S3: First, CsI, PbI2, SnI2, and SnF2 were dissolved in DMF and DMSO, stirred at room temperature for 3 h, and then 4-hydrazinobenzoic acid (HBA) was added and shaken to uniformly disperse HBA in the solvent to form a perovskite precursor solution. In the perovskite precursor solution, the concentration of CsI was 0.8 mol / L, the concentration of PbI2 was 0.4 mol / L, the concentration of SnI2 was 0.4 mol / L, the concentration of SnF2 was 0.04 mol / L, the concentration of HBA was 1 mg / mL, and the volume ratio of DMF to DMSO was 3:1; Step S3: 50 μL of perovskite precursor solution was spin-coated onto the hole transport layer at a speed of 5000 rpm for 60 s, followed by a two-stage annealing treatment, first at 85 °C for 1 min, then at 105 °C for 5 min, to form an all-inorganic tin-lead perovskite film. The all-inorganic tin-lead perovskite film is HBA-doped CsPb 0.5 Sn 0.5I3 polycrystalline film, wherein the molar ratio of HBA doping is 0.82%.

[0020] The method for preparing the all-inorganic tin-lead perovskite film of Example 2 is different from that of Example 1 in that, in Example 2, the concentration of HBA in step S3 is 3 mg / mL, and the prepared CsPb 0.5 Sn 0.5 In the I3 polycrystalline film, the molar ratio of HBA doping is 2.46%.

[0021] The method for preparing the all-inorganic tin-lead perovskite film of Example 3 is different from that of Example 1 in that, in Example 3, the concentration of HBA in step S3 is 7 mg / mL, and the prepared CsPb 0.5 Sn 0.5 In the I3 polycrystalline film, the molar ratio of HBA doping is 5.74%.

[0022] The method for preparing the all-inorganic tin-lead perovskite film of Comparative Example 1 is different from that of Example 1 in that HBA is not added when preparing the perovskite precursor solution in step S3 of Comparative Example 1, i.e., the CsPb 0.5 Sn 0.5 The I3 polycrystalline film is not doped with HBA. 0.5 Sn 0.5 I3 polycrystalline film is a traditional CsPb without any doping 0.5 Sn 0.5 I3 polycrystalline film.

[0023] Figure 1 CsPb of Example 2 0.5 Sn 0.5 SEM image of the surface of I3 polycrystalline film, Figure 2 CsPb of Comparative Example 1 0.5 Sn 0.5 SEM image of the surface of I3 polycrystalline thin film. Figure 3 CsPb of Example 2 0.5 Sn 0.5 The grain size distribution histogram of I3 polycrystalline thin film is shown in the figure. Figure 4 CsPb of Comparative Example 1 0.5 Sn 0.5 Grain size distribution histogram of I3 polycrystalline thin film. Figure 5 CsPb of Example 2 0.5 Sn 0.5 AFM image of I3 polycrystalline thin film, Figure 6 CsPb of Comparative Example 1 0.5 Sn 0.5 AFM image of I3 polycrystalline thin film. Figure 7 The CsPb of Example 2 and Comparative Example 10.5 Sn 0.5 XRD pattern of I3 polycrystalline thin film. Figure 8 The CsPb of Example 2 and Comparative Example 1 0.5 Sn 0.5 XPS pattern of I3 polycrystalline thin film. Figure 9 The CsPb of Example 2 and Comparative Example 1 0.5 Sn 0.5 Comparison pictures of the gradual decomposition of I3 polycrystalline films in air.

[0024] It can be seen that the CsPb of Comparative Example 1 without any doping 0.5 Sn 0.5 The surface of the I3 polycrystalline film is smooth and uniform, but has holes (see Figure 2 、 Figure 6 , Figure 2 The eight oval dotted boxes in the figure show larger holes), which may seriously affect the performance of the devices prepared subsequently; it is worth noting that when HBA is used and added to the perovskite precursor solution at a low concentration, the HBA-doped CsPb 0.5 Sn 0.5 The holes in the I3 polycrystalline film were significantly filled (see Figure 1 、 Figure 5 ), indicating that the crystallization during the formation of perovskite film is good. This proves that HBA is good for CsPb 0.5 Sn 0.5 The crystallization effect of I3 is significantly improved, which helps to obtain HBA-doped CsPb with uniform grain size, few grain boundary defects and preferred orientation. 0.5 Sn 0.5 I3 polycrystalline film.

[0025] like Figure 7 As shown, we can see that the CsPb 0.5 Sn 0.5 The I3 polycrystalline film shows the same diffraction peaks at 14.33° and 28.93°, which are typical B-γCsPb 0.5 Sn 0.5 Characteristic peaks of I3 perovskite. HBA doped CsPb in Example 2 0.5 Sn 0.5 The I3 polycrystalline film shows a better performance than the CsPb of Comparative Example 1 without any doping. 0.5 Sn 0.5 The higher characteristic XRD intensity of the I3 polycrystalline film confirms the effectiveness of HBA doping. Therefore, it can be confirmed that a HBA doping concentration of 3 mg / mL in the perovskite precursor solution is the optimal concentration for improving the surface quality of the perovskite film.

[0026] like Figure 8 As shown in the figure, after doping with HBA, the Pb 4f peak red-shifted, indicating that HBA to Pb through coordination 2+ Providing electrons optimizes the interface charge transfer, which can improve the energy level matching between the perovskite film and the hole transport layer, achieve defect passivation and interface energy level matching, thereby reducing non-radiative carrier recombination and helping to improve the open circuit voltage (Voc) and fill factor (FF) of the battery.

[0027] from Figure 9 It can be seen that under air conditions, due to the CsPb 0.5 Sn 0.5 I3 polycrystalline film is not doped with HBA. At 9 h, CsPb 0.5 Sn 0.5 The I3 polycrystalline film has almost completely absorbed water and oxidized and decomposed. 0.5 Sn 0.5 I3 polycrystalline film still maintains a relatively stable state, and the stability gap between the two is quite large. 0.5 Sn 0.5 I3 polycrystalline thin films will significantly improve the stability of solar cells.

[0028] The CsPb of Examples 1-3 and Comparative Example 1 were used respectively. 0.5 Sn 0.5 I3 polycrystalline thin film solar cell, which includes a conductive glass layer, a hole transport layer, a CsPb 0.5 Sn 0.5 I3 polycrystalline thin film, electron transport layer and metal electrode layer.

[0029] The electron transport layer is made of ZnO and PCBM. The preparation process of the electron transport layer is as follows: 15 mg ZnO is dissolved in 1 mL trifluoroethanol to obtain a ZnO solution, and the ZnO solution is spin-coated onto the CsPb substrate at a speed of 2500 rpm. 0.5 Sn 0.5 A ZnO layer was formed on the I3 polycrystalline film by spin coating for 60 seconds. Then, 20 mg of PCBM was dissolved in 1 mL of chlorobenzene to obtain a PCBM solution. This PCBM solution was then spin-coated onto the ZnO layer at 2500 rpm for 25 seconds to form the electron transport layer. Finally, a 100 nm thick metal electrode layer was formed on the surface of the electron transport layer by vacuum evaporation of Ag at a deposition rate of 0.9 Å / s, completing the solar cell.

[0030] Figure 10 For the CsPb of Example 2 and Comparative Example 10.5 Sn 0.5 JV curve (i.e. current density-voltage curve) of solar cells prepared with I3 polycrystalline thin film.

[0031] Using CsPb of Examples 1-3 and Comparative Example 1 0.5 Sn 0.5 The photoelectric parameters of the solar cell prepared by I3 polycrystalline thin film are shown in Table 1. The test conditions of the photoelectric parameters are AM1.5G and the light intensity is 100 mW / cm 2 . It can be seen from Table 1 that with the increase of HBA doping concentration, Voc (open circuit voltage), Jsc (short circuit current density), and FF (fill factor) all increase to a certain extent, thereby significantly increasing the photoelectric conversion efficiency of the solar cell. The photoelectric conversion efficiency corresponding to Example 2 in which the HBA doping concentration in the perovskite precursor solution is 3 mg / mL is the highest. However, when the HBA doping concentration rises to 7 mg / mL, Voc, Jsc, and FF all decrease to varying degrees, which directly leads to a decrease in the photoelectric conversion efficiency of the solar cell. The reason is that excessive HBA forms new grain boundaries during the crystallization process of the thin film, destroying the CsPb 0.5 Sn 0.5 Crystallization properties of I3.

[0032] Table 1

[0033] Combined with Table 1 and Figure 10 It can be seen that the CsPb 0.5 Sn 0.5 The solar cell prepared by I3 polycrystalline thin film achieved a photoelectric conversion efficiency of 7.47% and a short-circuit current density of 15.89 mA / cm 2 , the open circuit voltage is 0.77 V and the fill factor is 61.07%. 0.5 Sn 0.5 After HBA is doped into the I3 polycrystalline film, the CsPb 0.5 Sn 0.5 The photoelectric conversion efficiency of the solar cell prepared by I3 polycrystalline thin film is 14.31%, and the short-circuit current density is 19.97 mA / cm 2 , the open circuit voltage is 0.90 V, and the fill factor is 79.62%. The main reason for the increase in open circuit voltage is CsPb 0.5 Sn 0.5 Effective passivation of surface defects and reduction of non-radiative carrier recombination in I3 polycrystalline thin films.

Claims

1. A method for preparing an all-inorganic tin-lead perovskite thin film, characterized in that: The conductive glass layer is cleaned and dried, and then modified with a hole transport layer. The perovskite precursor solution is coated on the hole transport layer, and then annealed to form an all-inorganic tin-lead perovskite film. The all-inorganic tin-lead perovskite film is CsPb doped with 4-hydrazinobenzoic acid. 0.5 Sn 0.5 I3 polycrystalline film, the molar ratio of the 4-hydrazinobenzoic acid doped in the all-inorganic tin-lead perovskite film is 0.82-5.74%.

2. The method for preparing the all-inorganic tin-lead perovskite thin film according to claim 1, characterized in that: The perovskite precursor solution is formed by mixing CsI, PbI2, SnI2, SnF2, 4-hydrazinobenzoic acid and a solvent. In the perovskite precursor solution, the concentration ratio of CsI, PbI2, SnI2 and SnF2 is 1:0.5:0.5:0.05, the concentration of 4-hydrazinobenzoic acid is 1-7 mg / mL, and the solvent is at least one of DMF and DMSO.

3. The method for preparing the all-inorganic tin-lead perovskite thin film according to claim 2, wherein: In the perovskite precursor solution, the concentration of CsI is 0.6-1 mol / L, the concentration of PbI2 is 0.3-0.5 mol / L, the concentration of SnI2 is 0.3-0.5 mol / L, and the concentration of SnF2 is 0.03-0.05 mol / L.

4. The method for preparing the all-inorganic tin-lead perovskite thin film according to claim 3, wherein: In the perovskite precursor solution, the concentration of CsI is 0.8 mol / L, the concentration of PbI2 is 0.4 mol / L, the concentration of SnI2 is 0.4 mol / L, the concentration of SnF2 is 0.04 mol / L, and the concentration of 4-hydrazinobenzoic acid is 3 mg / mL.

5. The method for preparing the all-inorganic tin-lead perovskite thin film according to claim 2, characterized in that: The solvents are DMF and DMSO, and the volume ratio of DMF to DMSO is 3:

1.

6. The method for preparing the all-inorganic tin-lead perovskite thin film according to any one of claims 2 to 5, characterized in that: The preparation process of the perovskite precursor solution is as follows: first, CsI, PbI2, SnI2 and SnF2 are dissolved in a solvent, stirred at room temperature for 3 hours, then 4-hydrazinobenzoic acid is added, and then shaken to uniformly disperse the 4-hydrazinobenzoic acid in the solvent.

7. The method for preparing the all-inorganic tin-lead perovskite thin film according to claim 1, wherein: The annealing treatment is a two-stage annealing treatment, first annealing at 70-90°C for 1-2 minutes, and then annealing at 100-115°C for 4-6 minutes.

8. The method for preparing the all-inorganic tin-lead perovskite thin film according to claim 1, characterized in that: The hole transport layer is made of PEDOT:PSS.

9. The method for preparing the all-inorganic tin-lead perovskite thin film according to claim 8, wherein: The hole transport layer was prepared by diluting PEDOT:PSS with 3 times the volume of deionized water to obtain a PEDOT:PSS solution, spin-coating the PEDOT:PSS solution onto the conductive glass layer at a speed of 4000 rpm for 30 seconds, and then annealing at 120-180°C for 15-20 minutes.

10. Use of the all-inorganic tin-lead perovskite film according to any one of claims 1 to 9 in solar cells.

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