Synchronous defect passivation of all-inorganic perovskite solar cells enabled by fullerene interlayer

All-inorganic CsPbI_(3-x)Br_(x)perovskite solar cells(PSCs)are advantageous in terms of high thermal stability,while its efficiency lags behind those of organic-inorganic hybrid perovskite counterparts.Defect passivations have been extensively applied for enhancing efficiency of all-inorganic PSCs,which are mainly based on univocal defect passivation of perovskite layer.Herein,we incorporated a bis-dimethylamino-functionalized fullerene derivative(abbreviated as PCBDMAM)as an interlayer between ZnO electron transport layer(ETL)and all-inorganic CsPbI_(2.25)Br_(0.75)perovskite layer,accomplishing synchronous defect passivations of both layers and consequently dramatic enhancements of efficiency and thermal stability of PSC devices.Upon spin-coating PCBDMAM onto ZnO ETL,the surface defects of ZnO especially oxygen vacancies can be effectively passivated due to the formation of Zn−N ionic bonds.In addition,PCBDMAM incorporation affords effective passivation of Pb_(I)and I_(Pb)antisite defects within the atop perovskite layer as well via coordination bonding with Pb^(2+).As a result,the regular-structure planar CsPbI_(2.25)Br_(0.75)PSC device delivers a champion power conversion efficiency(PCE)of 17.04%,which surpasses that of the control device(15.44%).Moreover,the PCBDMAM-incorporated PSC device maintains~80%of its initial PCE after 600 h heating at 85°C hot plate in N2 atmosphere,whereas PCE of the control device degrades rapidly to~62%after 460 h heating under identical conditions.Hence,PCBDMAM incorporation benefited dramatic improvement of the thermal stability of PSC device.