Study On Defect Passivation Of Active Layer Additives In Mesoscopic Perovskite Solar Cells

Organic-inorganic hybrid perovskite solar cells（PSCs）show excellent photovoltaic performance.Among them,carbon-based fully printed mesoscopic perovskite solar cells（MPSCs）prepared by screen-printing technology have many advantages,including low cost,high stability,and the potential for large-scale and industrialized production.However,in carbon-based fully printed MPSCs,the lack of organic cations and halides in perovskite films can lead to insufficient coordination of Pb²⁺ions or the generation of Pb clusters.These defects may lead to non-stoichiometric charge and acting as a recombination center of charges leading to deterioration of device performance.In addition,the electron transport layer,Ti O₂,used in carbon-based fully printed MPSCs exsits mass of oxygen vacancy defects at the surface that will cause serious non-radiative recombination at the interface.Furthermore,the trap states may provide possibility for the penetration of moisture and oxygen into the perovskite layer,leading to deterioration of device stability.Therefore,the article thesis focuses on the modification of the active layer and the improvement of the photovoltaic performance of carbon-based fully printed MPSCs devices by the introduction of additives to passivate the defects of the perovskite and Ti O₂/perovskite interfaces.The thesis includes the following two researches:（1）By introducing ethylene carbonate（EC）into the perovskite layers as an additive,the optimized MPSCs obtain a power conversion efficiency（PCE）of 15.28%that is 17%higher than that of the MPSCs without EC.And in an environment the unpackaged MPSCs with EC maintains more than 90%of the initial performance after stored in air with a humidity of 60±10%.Through density functional theory calculations and experimental analysis,it is shown that the C=O functional group contained in EC has a pair of electrons that can passivate the defects of insufficient coordination in the active layer of perovskite in carbon-based fully printed MPSCs.A proper amount of EC can reduce the defect density in the perovskite layers and effectively inhibit the non-radiative recombination at the grain boundary.In addition,the introduction of EC can also increase the coverage and pore filling of the perovskite on the mesoscopic Ti O₂ scaffold.This synergistic effect can improve device performance and achieve excellent device stability.Therefore,all the results show that the introduction of additive EC can effectively passivate the defect state,which provides a simple method for preparing high-performance carbon-based fully printed MPSCs.（2）We successfully prepared carbon-based fully printed MPSCs by introducing methylamine acetate（MAAc）into the perovskite layer as an additive.The experimental results show that adding an appropriate amount of MAAc can effectively passivate the oxygen vacancy defects at the Ti O₂/perovskite interface and the defects in perovskite layers,which improve the charge transfer efficiency and inhibits the non-radiative recombination at the Ti O₂/perovskite interface,and reduce the defect density in perovskite layers effectively.In addition,MAAc additives improve the filling of the precursor solution in the mesoporous scaffold and the film crystallization of the perovskite layers.As a result,the PCE of the MPSCs with MAAc is improved to 15.61%that is about 13%higher than that of MPSCs without MAAc.In addition,after 55 days of aging in air with a humidity of 60±10%,the MPSCs with MAAc maintained more than 90%of the initial PCE,showing excellent long-term stability.Therefore,this work provides a simple and effective strategy for preparing efficient and stable carbon-based fully printed MPSCs.