Crystal Growth Regulation And Photovoltaic Properties Of Tin-based Perovskites

In recent years,lead-based perovskite solar cells(PSCs)have been widely studied in the field of photovoltaics because of their excellent optoelectronic performance.The power conversion efficiency of PSCs has rapidly soared from 3.8%in 2009 to 25.7%in2021.However,most of these high-performing PSCs are based on lead-based compositions,where the lead toxicity is potentially harmful to the environment.Meanwhile,tin(II)-based perovskites have many advantages,such as low toxicity,small bandgaps,and high charge carrier mobility,which are therefore considered as the most promising lead-free perovskite alternatives.Nevertheless,the highest power conversion efficiency based on pure tin(II)-based PSCs is 14.81%,which is significantly lower than the highest theoretical efficiency(33.4%).The relatively low efficiency of tin(II)-based PSCs is mainly attributed to the Sn²⁺oxidation and uncontrollably fast crystallization of thin films.As such,this work innovatively adopts eco-friendly antioxidant—epicatechin and lamination annealing method to prepare oxidation resistant and high-quality PEA_0.15FA_0.85Sn I₃ thin films with minimal pinholes,and achieves remarkable optoelectronic performance on tin(II)-based PSCs.The main research contents of this thesis are as followed:1.Eco-friendlyadditive epicatechin was added into tin(II)-based perovskite as antioxidant and greatly improved the chemical stability of thin films.In addition,the introduction of epicatechin significantly reduced pinholes,enhanced the light absorption and decreased the density of defect states within tin(II)-based perovskite films,while suppressing non-radiative recombination of charge carriers.As a result,solar cell devices with epicatechin antioxidant achieved a short-circuit current density of 16.07 m A/cm~2and obtained a power conversion efficiency of 6.01%.2.Growth and crystallization kinetics of tin(II)-based perovskite films can be regulated via lamination method to control the volatilization rate of organic solvent dimethyl sulfoxide(DMSO)during the film annealing process.After employing the lamination annealing method,crystallinity and surface quality of PEA_0.15FA_0.85Sn I₃ thin films was improved and the density of defect states was reduced.Consequently,champion device exhibited an open-circuit voltage of 0.63 V and a power conversion efficiency of 7.10%.In this work,eco-friendly antioxidant was employed in combination with lamination annealing method to regulate the growth and crystallization kinetics of tin(II)-based perovskite films and improved the material stability and device performance,thus providing new strategy for achieving efficient and stable tin(II)-based PSCs.