Photoelectric Performance And Optimizated Preparation Of CsPbIBr₂ All-Inorganic Perovskite Layer

In recent years,perovskite materials have attracted much attention due to their excellent light absorption properties,low exciton binding energy and long carrier lifetime.Among them,the photoelectric conversion efficiency of organic-inorganic hybrid perovskite solar cells has reached 25.7%,but the introduction of organic cations has greatly reduced the wet and thermal stability of perovskite materials,and hindered the commercialization of the cells.In order to solve these problems,scientists have made many attempts,among which the preparation of inorganic perovskite with Cs⁺ions instead of organic ions has been proved to be an effective method.CsPbIBr₂perovskite has been widely concerned for its suitable band gap and good environmental stability.However,the CsPbIBr₂perovskite layer still has some problems,such as low film coverage,many defects and poor overall quality.Based on the FTO/c-TiO₂/m-TiO₂/CsPbIBr₂/Spiro-OMe TAD/Ag structure of perovskite solar cells,this paper aims to prepare continuous and regular perovskite layers,reduce the surface trap state,improve the film forming quality of perovskite layers,and improve the photoelectric performance of solar cells.The specific research contents are as follows:By adjusting the preheating temperature of FTO conductive substrate,the coverage rate of CsPbIBr₂layer was improved.Suitable preheating temperature can promote the explosive nucleation of inorganic perovskite precursor on the surface of the substrate material,achieve full coverage of CsPbIBr₂layer,and significantly improve the crystallinity of the crystal.Then,the growth of CsPbIBr₂crystal nuclei is controlled by gradient annealing process.When the preheating temperature is 60℃,the time is 10 min,and the annealing time is 1 min,1 min and 10 min at 100℃,150℃and 250℃,respectively.The CsPbIBr₂perovskite layer with flat surface,compact surface and no pinholes is obtained,and the efficiency of the assembled device is 7.74%.In order to promote the lattice shrinkage of perovskite,reduce the surface trap state of perovskite,and reduce the probability of non-radiative recombination,the Li⁺doped CsPbIBr₂absorption layer was obtained by introducing different doping concentrations of Li⁺ions to replace Cs⁺ions in the CsPbIBr₂perovskite precursor solution.The results show that the surface of the Li+doped perovskite layer is continuous and regular,and the crystallinity of the grains in the film is better than that of the undoped perovskite layer.The CsPbIBr₂cells doped with Li⁺have higher parallel resistance,higher photoelectric conversion efficiency and lower hysteresis coefficient.When the Li⁺doping ratio in the CsPbIBr₂absorbing layer is 2 mol%,the photoelectric conversion efficiency of the assembled solar cell is 9.51%,and the hysteresis coefficient is 8%.Compared with the undoped Li⁺battery,the photoelectric conversion efficiency is increased by 18%,and the hysteresis coefficient is reduced by 50%.Compared with the undoped Li⁺solar cell,the photoelectric conversion efficiency is increased by 18%,and the hysteresis coefficient is reduced by 50%.