Highly Stable All-Inorganic Perovskite Solar Cells Processed at Low Temperature

All-inorganic perovskites such as cesium lead bromide (CsPbBr3) can show much better stability than organic-inorganic hybrid perovskite materials in ambient air. However, fabricating a high-quality CsPbBr3 perovskite film normally requires a high annealing temperature, leading to the difficulty of preparing CsPbBr3 solar cells with low-temperature solution process. In this work, we demonstrated a pyridine-vapor treatment in two-step fabrication of CsPbBr3 perovskite films that can reduce the annealing temperature to about 160 degrees C. The mechanism is attributed to the reaction of pyridine with lead bromide, which forms an intermediate phase and leads to a low activation energy in the formation of CsPbBr3 perovskite films during thermal annealing. The devices without encapsulation show excellent stability in ambient air with the humidity up to 70%. This work provides a novel approach for preparing inorganic perovskite solar cells at low temperature.