Performance Improvement Of All-Inorganic Perovskite Solar Cells By Additives And Interface Engineering

The all-inorganic perovskite is a type of perovskite materials formed by replacing organic cations with inorganic cesium cations,which has better thermal stability compared to organic-inorganic hybrid perovskites,thus gradually becoming an important research branch in the field of perovskite solar cells（PSCs）.In recent years,research on all-inorganic PSCs has made significant progress.However,the power conversion efficiency（PCE）of all-inorganic PSCs is still below its theoretical limit.Therefore,using additives and interface engineering methods to optimize inorganic perovskite films and improve the performance of inorganic PSCs is still of great significance.This dissertation flexibly applies additive and interface engineering strategies,focusing on the defect and stress regulation of inorganic perovskite films,energy level regulation of inorganic PSCs devices,and conducts in-depth research on performance improvement schemes of inorganic PSCs.The specific research content is as follows:（1）By using lithium acetate（LiAc）additive to regulate the crystallization process of CsPbI₂Br perovskite,the formation of poor intermediate phase CsBr during CsPbI₂Br crystallization process was effectively suppressed,thereby significantly improving the quality of CsPbI₂Br films.The results indicated that the generation of CsBr can induce the formation of iodine rich phase CsPbI_2+xBr_1-x,ultimately leading to a decrease in the quality of CsPbI₂Br perovskite films after annealing.After being regulated by LiAc,the CsBr and iodine rich phase CsPbI_2+xBr_1-x during the crystallization process of CsPbI₂Br were significantly reduced,and the crystallinity of CsPbI₂Br perovskite films was significantly improved after annealing.Meanwhile,benefited from the delayed crystallization effect of LiAc,the grain size of CsPbI₂Br was increased.In addition,Li⁺regulated the energy level of CsPbI₂Br perovskite to promote charge extraction and transport of PSCs;Ac^-passivated uncoordinated Pb²⁺on the surface and grain boundaries of perovskite to reduce defects in perovskite films and further optimize charge transfer characteristics.Ultimately,the crystallization kinetics regulation of LiAc additive resulted inCsPbI₂Br PSCs achieving a maximum PCE of 16.05%and exhibiting excellent thermal stability,with no significant degradation in performance after aging at 85°C for over 300 hours.（2）The methylammonium chloride（MACl）additive was used to further regulate the crystallization process and increase the grain size of CsPbI₂Br.An in-depth analysis was conducted on the abnormal phenomenon of PCE reduction in devices,revealing the non-uniform residual characteristics of MACl in inorganic perovskite CsPbI₂Br.The residual Cl^-caused local lattice expansion,exacerbated the residual stress of CsPbI₂Br films,and lead to interface energy level mismatch.To solve this problem,a potassium acetate（KAc）interface layer was introduced to achieve the substitution of A-site cations inCsPbI₂Br and achieved local lattice contraction,thereby offsetting the lattice distortion effect of Cl^-and reducing films stress.In addition,Ac^-passivated defects in the electron transport layer（ETL）of tin oxide（SnO₂）,reducing charge non-radiative recombination.Ultimately,this strategy of combining MACl additive engineering with KAc interface engineering resulted inCsPbI₂Br PSCs achieving a maximum PCE of 17.11%.（3）The simultaneous passivation of anionic and cationic defects inCsPbI₂Br perovskite layers using 4-（chlorosulfonyl）benzoic acid（CSBA）additive effectively suppressed the light soaking（LS）effect in p-i-n type CsPbI₂Br PSCs.The results indicated that the effect was mainly dominated by photo-induced defect passivation,and mainly occured in the CsPbI₂Br perovskite layer.The LS effect inhibition principle of CSBA has the following two points:firstly,CSBA can generate I₃^-in-situ with the participation of I^-and solvent,effectively passivating the anionic halogen vacancy defects inCsPbI₂Br.Secondly,the Lewis base groups onCSBA can effectively passivate the uncoordinated cation defects inCsPbI₂Br.Ultimately,the CsPbI₂Br films regulated by CSBA exhibited higher crystallinity and larger grains,and the energy levels of CsPbI₂Br PSCs were more matched,effectively suppressing the LS effect.（4）Based on the low-temperature preparation of SnO₂ ETL and undoped polymer poly（3-hexylthiophene-2,5-diyl）（P3HT）hole transport layer（HTL）,the performance of Cs₂AgBiBr₆ PSCs was significantly improved by introducing an InCl₃ modification layer at the SnO₂/Cs₂AgBiBr₆ interface.The InCl₃ modification layer acted on both SnO₂ and Cs₂AgBiBr₆ simultaneously,and the performance improvement principle has the following two points:firstly,In³⁺could be embedded into Cs₂AgBiBr₆ to achieve partial substitution of B-site cations,making B⁺and B³⁺alternately arranged in an orderly manner,thereby reducing the defects of Cs₂AgBiBr₆ films,improving the crystallinity and quality of the films.Secondly,InCl₃ could interact with SnO₂ to improve the conductivity of ETL.In addition,the energy levels of Cs₂AgBiBr₆ PSCs modified by the InCl₃ interface were more matched,which was conducive to the extraction and transmission of charges at the two interfaces.Ultimately,the Cs₂AgBiBr₆PSCs modified by InCl₃ interface achieved a maximum PCE of 1.27%,which was nearly 57%higher than the control PSCs.