Preparation And Characterization Of High Efficiency Tin-lead Mixed Perovskite Photovoltaic Cells

Organic-inorganic hybrid perovskite materials have attracted extensive attention because of their high optical absorption coefficient,high carrier mobility and diffusion length,direct adjustability of optical band gap and processability in low temperature solution.At present,PSCs has reached 25.7%certified PCE.However,lead,which is widely used in perovskite materials,is highly toxic and has a serious impact on the environment,which also affects the commercialization process of PSCs.Narrow band gap Sn-Pb mixed perovskite materials stand out among many lead-free perovskite materials because of their low toxicity,high electron mobility and low exciton binding energy.Although narrow band gap Sn-Pb mixed PSCs have developed rapidly in recent years,the photoelectric conversion efficiency(PCE)has been significantly improved.However,a large number of defects in Sn-Pb mixed perovskite materials hinder its further application:(1)The oxidation of Sn²⁺leads to a large number of p-type self-doping in perovskite films;(2)The rapid crystallization of Sn-Pb mixed perovskite leads to poor film quality.Therefore,the crystallization properties,film morphology and the stability of PSCs of Sn-Pb mixed perovskite still face major challenges.The thesis focuses on the performance optimization of narrow band gap Sn-Pb PSCs by using the optimization strategy of additive engineering.It mainly includes the following two aspects:1.By exploring the preparation process of Sn-Pb mixed perovskite,the optimal preparation conditions of solar cells in the Sn-Pb mixed perovskite system were successfully obtained,and the photoelectric conversion efficiency of 17.77%was preliminarily obtained.It lays a foundation for the following experiments.2.By adding 4-hydrazine benzoic acid(HZBA)reducing agent as an additive to the tin lead mixed perovskite precursor solution,the oxidation of Sn²⁺in the perovskite precursor solution is effectively inhibited.At the same time,the strong interaction between HZBA,Sn I₂ and Pb I₂ effectively passivates the surface defects of tin-lead mixed perovskite films,and optimizes the crystallinity and surface morphology of perovskite films.In addition,HZBA optimizes the energy band structure of perovskite and promotes the charge transfer between perovskite and ETL.Finally,the PCE of tin lead mixed PSCs prepared based on HZBA additive engineering increased from 18.3%of the standard sample to 21.1%,and enhanced the stability of Sn-Pb mixed PSCs.In this work,phenylhydrazine was added to the Sn-Pb mixed perovskite precursor solution for the first time.Through the reducibility of phenylhydrazine and the interaction between carbonyl and Sn²⁺/Pb²⁺,the photoelectric properties and stability of Sn-Pb mixed PSCs were improved,and the development of narrow-band gap Sn-Pb mixed PSCs and full perovskite laminated cells were further promoted.