Study On The Defect Passivation And Optoelectronic Performance Of Lewis Base For Perovskite Solar Cells

Perovskite materials have made significant progress in the field of solar cells in recent years due to their high diffusion coefficient,shallow energy level defects,and other advantages.The power conversion efficiency（PCE）of perovskite solar cells（PSCs）has increased from 3.8%to 25.7%.However,compared to the Shockley-Queisser limit efficiency（30.5%）of single-junction PSCs,the current efficiency of the device still has a large gap.This is mainly due to carrier recombination losses caused by defects at the interface and inside the perovskite.In addition,the degradation of PSCs primarily occurs at the surface and grain boundaries of the perovskite films.Reducing vacancy defects is beneficial for achieving long-term stable PSCs.Therefore,in order to reduce the defects at the interface and grain boundaries,this article adopts the approach of modifying the interface and doping in the bulk to minimize energy loss of charge carriers,thereby improving the performance of devices.The specific research content is as follows:Firstly,addressing the defects at the buried interface in n-i-p type planar solar cells,α-cyano-4-hydroxycinnamic acid（CHCA）is employed to modify the interface between Sn O₂ and perovskite layer in this paper,so as to reduce charge loss and recombination and maximize the device efficiency.The results show that the modification of Lewis base functionalized molecules CHCA not only passivated oxygen vacancy defects in Sn O₂,but also passivated organic cationic,halogen vacancy defects and free iodide ion defects in perovskite.As the defect density decreased,the PCE increased from 19.79%for unmodified devices to 23.02%for modified device.And after aging for 1500 h at15-20%relative humidity,the unpackaged modified device maintained 94.2%of the initial efficiency,while the control device only maintained 87.6%of the original efficiency.In a dark environment with a temperature of 60℃,the unencapsulated and modified device retains 74.0%of original performance after 340 hours of aging.In the same environment,the control device only maintains 24.4%.Second,considering the presence of grain boundary defects in perovskite films,this paper utilized 5-Benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid（HMS）as an additive to modify perovskite films.By enlarging the grain size of the perovskite,the occurrence of grain boundary defects can be mitigated,leading to enhanced performance.The experimental findings indicate that the addition of HMS effectively passivated defects in the perovskite films,reducing trap centers for capturing charge carriers,and particularly improving V_OC and FF.Compared to modifying the interface,the HMS additive demonstrated better optoelectronic performance,achieving the PCE of 21.93%,which is much higher than the PCE of 19.32%of the control device.In addition,the index of hysteresis HI is also reduced from the original 0.0301 to 0.0023of the devices doped with HMS,which is even negligible.More importantly,after a550-hour air exposure experiment under dark conditions,the air-exposed devices doped with HMS retained 98.0%of initial efficiency,demonstrating excellent humidity stability.In contrast,the control devices showed poorer stability,retaining only 91.6%of initial efficiency.In conclusion,this article takes reducing defect density and minimizing voltage loss as effective strategies.By utilizing CHCA passivation at the interface defects and HMS passivation at the grain boundary defects,the capture and recombination of carriers in the n-i-p type devices of planar structure are effectively reduced,resulting in improved the performance of devices.This approach not only yields successful results in this study but also provides valuable reference for the investigation of other optoelectronic devices.