Perovskite solar cells (PSCs) based on organometallic halide have received wide attention and been developed rapidly in recent years, the highest power conversion efficiency (PCE) have reached 22.1%. However, these materials contain lead (Pb), which is toxic. It is of critical importance to find new elements for partially or completely replacing Pb to reduce the Pb contents. Most works carried out focused on CsSnX₃ (X=I, Br), FASnX₃ (X=I, Br), (FASnI3)_1-x(MAPbI3)_x (x=0-1), MASn_xPb_1-xI₃ (x=0.25, 0.5), FA_0.75Cs_0.25Pb_0.5Sn_0.5I₃, etc. We substitute PbI₂ with SnI₂ in Cs_0.05(MA_0.17FA_0.83)_0.95Pb(I_0.83Br_0.17)₃ material for the first time, through changing the ratio of Pb and Sn, which can regulate the size of grains. By optimizing the ratio of PbI₂ and SnI₂ to achieve the best energy band matching, a power conversion efficiency of 16.10% is achieved by using Cs_0.05FA_0.79(Pb_0.6Sn_0.4)_0.84I_2.5MA_0.16Pb_0.16Br_0.5 as perovskite light absorption layers. With bandgap changing, the hysteresis of the PSCs showed regular variation. Under the optimal bandgap matching, the planar heterojunction PSCs exhibit J-V curves with negligible hysteresis.

Figure 1. a)-f) The reverse and forward voltage scans of Cs_0.05FA_0.79(Pb_1-xSn_x)_0.84I_2.5MA_0.16Pb_0.16Br_0.5 (x=0, x=0.1, x=0.2, x=0.3, x=0.4, x=0.5) perovskite solar cells.