Research On The Cathode Interface Based On N-i-p Structure Perovskite Solar Cells

Perovskite solar cells（PSCs）have received extensive attention in recent years due to their high efficiency,low cost,and solution preparation.Although perovskite solar cells have developed rapidly,there are still some problems that hinder the further improvement of cell power conversion efficiency（PCE）,such as interface defects and interface energy level mismatch.Tin dioxide（SnO₂）is currently the most common and effective cathode interface material used in perovskite solar cells,especially in the efficient n-i-p structure,which can improve the quality of cathode interface and improve performance.However,there are hydroxyl and oxygen vacancy defects on the surface of SnO₂,resulting in a large defect state density at the cathode interface and serious interface non-radiative recombination.In this paper,inorganic antimony trifluoride（SbF₃）and ammonium iodide（NH₄I）were introduced to dope SnO₂respectively,they can improve the SnO₂film quality,reduce the interface defect state,and improve the performance and stability of the perovskite solar cells.At the same time,it was found that using SbF₃or NH₄I as the cathode interface layer can also prepare high performance and stable perovskite solar cells.The main work is as follows:SbF₃and NH₄I cathode interface modification layers for perovskite solar cells:Considering the poor energy level matching between FTO and perovskite layers,SbF₃and NH₄I were introduced to modify the FTO substrate in this work.PSCs with the structure of FTO/SbF₃（or NH₄I）/Cs_0.05(FA_0.83MA_0.17)_0.95Pb(I_0.84Br_0.16)₃/Spiro-OMe TAD/Ag were prepared.Compared with the control device,the photovoltaic performance of the device based on the SbF₃and NH₄I cathode interface is significantly improved.By further adjusting the ratio of SbF₃and NH₄I,the PCE of the device was increased from 14.26%to 16.64%and 16.72%,respectively.The results show that the SbF₃and NH₄I modified layers can effectively increase the perovskite crystallinity,improve the energy level between the FTO and the perovskite layer,reduce the defect state density at the cathode interface,promote charge transport and extraction,and suppress the hysteresis effect of the device.SbF₃-doped SnO₂ for planar n-i-p perovskite solar cells:Based on the above work of SbF₃,in order to better study the cell interface,this work further doped SbF₃into SnO₂colloidal dispersion and fabricated PSCs with the structure of ITO/SnO₂-SbF₃/（FAPb I₃）_1-x(MAPb Br_3-yCl_y)_x/Spiro-OMe TAD/Au.By optimizing the doping ratio of SbF₃in SnO₂,the PCE of the device was increased from 19.89%to 21.42%.The research results show that the incorporation of SbF₃can improve the electron mobility of SnO₂,enhance the crystallinity of perovskite films,suppress the residual amount of Pb I₂in the perovskite layer,and improve the film quality and energy level matching at the SnO₂/perovskite interface,reduce the interface defect density,and therefor suppress the non-radiative recombination of the device.Furthermore,the devices based on the SnO₂-SbF₃electron transport layer exhibit excellent stability with negligible hysteresis effect.NH₄I-doped SnO₂ for planar n-i-p perovskite solar cells:The above studies show that the NH₄I cathode interfacial layer is conducive to the growth of perovskite crystals.In this work,NH₄I is further doped into SnO₂colloidal dispersion to prepare the perovskite solar cells with structure of FTO/SnO₂-NH₄I/Cs_0.05(FA_0.83MA_0.17)_0.95Pb(I_0.84Br_0.16)₃/Spiro-OMe TAD/Ag.By optimizing the doping ratio of NH₄I,the device efficiency was increased from 16.44%of the control device to18.65%.The research results show that the electron mobility is significantly improved after NH₄I doping,the energy level matching between the SnO₂-NH₄I electron transport layer and the perovskite layer is improved,the quality of the perovskite film is significantly improved,and the density of well states in the perovskite layer is reduced and carrier recombination is suppressed.Furthermore,the devices based on the NH₄I-doped SnO₂electron transport layer exhibit negligible hysteresis effect and excellent stability.