Simultaneously enhanced efficiency and ambient stability of inorganic perovskite solar cells by employing tetramethylammonium chloride additive in CsPbI2Br

Although all-inorganic perovskites possess suitable bandgap and thermal stability for photovoltaic applications, the unstable film morphologies, and poor moisture stabilities lag behind the organic-inorganic hybrid counterparts. Herein, we demonstrate that high quality α-CsPbI2Br films with improved phase stability, high crystallinity, and pinhole-free film morphology was achieved by employing tetramethylammonium chloride (TMACl) as an additive. As a result, the TMACl-added CsPbI2Br films exhibited high power conversion efficiency of 14.12% with an open-circuit voltage of 1.19 V, a short-circuit current density of 15.08 mA/cm2, and a fill factor of 0.78. More importantly, the TMACl addition imparts hydrophobicity to the film surface of CsPbI2Br, which delivered excellent stability up to 30 days in the ambient condition and thermal stability at 85 °C for 156 h, respectively. Moreover, the TMACl-added device also exhibited excellent PCE of 27.16% under indoor light source (1000 lux), which presents a promising approach for designing stable but high performance all-inorganic perovskite solar cells.