High-Performance All-Inorganic CsPbBr3 Perovskite Solar Cells Fabricated using Two-Step Spin-Coating Method with NH4Ac Additive in the CsBr/H2O Solution

Abstract

All-inorganic CsPbBr3 perovskite solar cells exhibit excellent humidity and thermal stability compared with organic-inorganic hybrid perovskite solar cells. However, the proposed two-step spin-coating method for fabricating CsPbBr3 film using highly concentrated CsBr/H2O solution in the second step is prone to result in CsPbBr3 film with high defect density, which greatly limits the performance of CsPbBr3 perovskite solar cells. In this study, appropriate amount of NH4Ac is used as additive in the CsBr/H2O solution. The interaction of NH4Ac with CsPbBr3 could contribute to smooth and densified CsPbBr3 perovskite films with suppressed defect density. When carbon electrode based CsPbBr3 perovskite solar cells are fabricated, an optimized photovoltaic conversion efficiency of 8.77% is achieved using 0.50 mg mL-1 NH4Ac in CsBr/H2O solution, which is 23.35% higher than that of the reference perovskite solar cell (champion PCE = 7.11%). Furthermore, the optimized CsPbBr3 perovskite solar cell exhibits better long-term stability, which can maintain more than 85% of its initial efficiency after being placed for 30 days at an ambient temperature of 25 °C and a relative humidity of 30%~40%.