Optimization Of Seauential Deposition Prepared High Efficiency Perovskite Solar Cell

Owning to the remarkable optoelectronic properties such as excellent light absorption coef-ficient,high defect tolerance,extremely long carrier life,simple preparation process,low cost,etc.,organic-inorganic hybrid perovskite has been regarded as one of the most promising photo-voltaic materials.This star material has huge commercial application potential.Especially in the photovoltaic field.Thin-film solar cells with perovskite as the active layer have been developed rapidly in recent years and have reached a power conversion efficiency（PCE）,which is compa-rable to commercial polysilicon.Nowadays,stability is the main problem which limit it been ap-plied large-scale application.Numerous efforts have been attempted to solve this issue including component engineering,process engineering,interface engineering,and solvent engineering.At present,the research of perovskite solar cells mainly focuses on the two systems:FAPbI3 and MAPbI3.While the thermal stability of MAPbI3 is rather poor,and pure FAPbI3 is very easy to convert into yellow phase at room temperature.Therefore,more and more solar cell devices tend to use A-site doping strategies aimed towards high efficiency and stabile devices.In this work,we take the formal perovskite solar cell as the basic structure（ITO/SnO2/perovskite/spiro-MeOTAD/MoO3/Ag）.We first carried out the adjustment of the A-site composition and found that compared with the double-cation（MA/FA or Cs/FA）system,the devices prepared with the three-cation（FA/MA/Cs）component not only has better luminance stability,but also has much higher efficiency.The champion device efficiency reaches 23.02%.We also found that when using the two-step method to prepare the perovskite film,the hu-midity during the second step reaction has a huge impact on the performance of the final device.Through the characterization and analysis of perovskite films grown at 0%,20%,35%,and 60%humidity,we found that the film prepared under 35%humidity conditions which obtained best performance has significant differences in crystallinity,carrier lifetime,defect state density,etc.We use Time of Flight Secondary Ion Mass Spectrometry（TOF-SIMS）to deny the mainstream speculation that water affects the crystal quality by affecting the inter-diffusion degree of the films.With analysis of the scanning electron microscope（SEM）images,we exclude the influence of water on the grain size.With theoretical derivation,we confirmed that humidity affects the film quality and the trap density mainly by affecting the crystallization rate during the perovskite growth process,thus affecting PCE of devices.