Study Of Preparation And Performance Of Tin Oxide As Electron Transport Material In Planar Heterojunction Perovskite Solar Cells

Organic-inorganic lead halide perovskite is an excellent absorbent material,which is used in solar cells to achieve high photoelectric conversion efficiency.SnO₂ has become the most promising electron transport material due to its high conductivity,low preparation temperature and chemical stability..In this thesis,a planar heterojunction perovskite solar cells?PSCs?with MAPbI₃ as absorbent layer was prepared by using SnO₂ compact layer as electron transport material.The factors influencing the preparation of SnO₂ electron transport layer,the effect of doping different elements on the electron transport performance of SnO₂ and the optimization scheme of MAPbI₃ absorption layer were studied.The main contents of the thesis are as follows:The effects of different sol-gel treatment temperature,aging time and water content on the properties of SnO₂ electron transport layer and efficiency of the PSCs were studied.The experimental results show that the proper treatmenttemperature of the sol-gel is beneficial to promote the formation of SnO₂ and improve the efficiency of SnO₂ electron transport.A longer aging duration is favorable to the crystallization of SnO₂,and the SnO₂ with good crystallization has high electron transport efficiency.The addition of proper amount of water to the sol-gel precursor is beneficial to the hydrolysis of SnCl₂ to promote the formation of SnO₂ and ultimately to improve the efficiency of PSCs.By comparing the efficiency of SnO₂based planar heterojunction PSCs prepared under different conditions,we determined sol-gel treatment temperature at 80?,and at the same time dropping 150?L of water to prepare SnO₂ sol-gel and aging 24 h to prepare SnO₂ electron transport layer.Optimizing the electron transport layer by doping SnO₂ to improve the conversion efficiency of PSCs.After doping Sn⁴⁺by Li⁺,Mg²⁺,Ga³⁺,and Ti⁴⁺which possess similar ionic radii of,the electron transfer ability of SnO₂ was enhanced.After doping with Li⁺,Mg²⁺,and Ga³⁺,the J_scc was increased significantly.In addition,whendoped by Ga³⁺and Ti⁴⁺,the performance of the solar cell and V_occ were enhanced After doping with Al³⁺,Ga³⁺,and In³⁺,it is found that J_scc increases with increasing doping ionic radius.SnO₂ doping by the ion which have the same radius of Sn⁴⁺can effectively improve the FF value and improve the performance of SnO₂-based planar heterojunction PSCs.The effects of concentration of MAPbI₃ precursor,heat treatment time and anti-solvent selection on the performance of PSCs were studied.It is found that the thickness of the MAPbI₃ film is determined by the concentration of the precursor,and the optimal concentration of the MAPbI₃ precursor is 1.2 M,and the efficiency of PSCs obtained is12.66%.The appropriate heat treatment time is beneficial to the formation and crystallization of MAPbI₃.The optimal heat treatment time is 5 min,and the efficiency of PSCs is increased to 13.15%.Anti-solvent selection has an important effect on the macroscopic and microscopic morphology of MAPbI₃ thin films.The morphology of MAPbI₃ thin films has an important effect on the performance of the PSCs.Using chlorobenzene as the anti-solvent,the macroscopically transparent and microcrystalline MAPbI₃ thin films can be prepared which can lead to excellent efficiencies for PSCs.