The Application Of Fused-ring Non-fullerene Electron Accepter For Improving The Photovoltaic Performance And Stability Of Perovskite Solar Cells

Due to the fast development of perovskite solar cells(PSCs)in the past decade,the power conversion efficiencies(PCEs)of PSCs have been increased from 3.8%to 25.2%,which attracts great attention of researchers in the field of photovoltaics.Although the PCEs of PSCs approach those of silicon-based solar cells,the poor stability and limited lifetime of PSCs impede their progress towards commercialization.The inverted structure perovskite solar cells have many advantages such as lowtemperature fabrication,negligible hysteresis,and application on flexible devices,which show great potential for future photovoltaic applications.We started our research work on optimizing the PCE and stability for inverted perovskite solar cells.This thesis mainly focuses on work for further improving the PCE and stability of perovskite solar cells.The main contents of this thesis are as follows:1.To improve the film quality of perovskite,a fused-ring non-fullerene electron acceptor 6TIC was used to passivate the defect sites inside bulk MAPbI3 perovskite.Due to the lone pair electrons provided by the N atom in the 6TIC molecule,Lewis acid-base interaction occurs between the unsaturated Pb in perovskite and 6TIC,which reduces the density of such trap states based on unpaired Pb.Due to the electron acceptor property of the fused-ring molecular,the electron extraction ability of 6TIC doped perovskite was also improved.As a result,perovskite solar cells with absorber layers doped by 6TIC achieved champion PCE of 19.08%,demonstrating that 6TIC can passivate the defects inside perovskite bulk phase and improve the electron extraction ability of devices.2.In order to improve the device stability of PSCs while maintaining optimal photovoltaic performance,we followed the same molecular doping strategy in our previous works.We modified 6TTC molecule with fluorine atom to obtain a new molecule DT4F.Because of the presence of fluorine,the hydrophobicity of DT4F has further enhanced.After DT4F molecule was introduced into the grain boundary of perovskite,it can passivate the defects of perovskite by Lewis base-acid interaction and improve the device stability against water because of its hydrophobicity.Unencapsulated PSC based on perovskite doped with DT4F can maintained about 93%of its initial PCE after 18 days storage under ambient conditions.Our research presents that designing doping molecule and optimizing doping strategy can help increasing the photovoltaic performance and stability of PSCs simultaneously.