Dual Passivation Strategy for High Efficiency Inorganic CsPbI2Br Solar Cells

Inorganic metal halide perovskite solar cells have achieved incredible progress in recent years. However, the power conversion efficiency of the inorganic perovskite solar cells is still low compared with their hybrid counterparts due to the inescapable nonradiative losses from the charge recombination. Herein, a strategy is demonstrated to minimize the nonradiative recombination loss in CsPbI 2 Br solar cells by establishing a synergetic passivation from the mutual effect of alkali‐ and alkylammonium‐salt. Accordingly, a sequential passivation process employing KBr and phenethylammonium chloride overcomes their limited passivation effect in one single step. This dual passivation is beneficial to an improved CsPbI 2 Br film with reduced trap defects, enlarged grain size, as well as to form an ultrathin low‐dimensional perovskite surface layer. As a result, a very high power conversion efficiency of 16.9% is obtained for inorganic CsPbI 2 Br solar cells. The proposed dual passivation scheme provides a feasible route not only for the design of high‐efficiency perovskite solar cells but also for other perovskite‐related optoelectronic devices.