Hot-substrate deposition of all-inorganic perovskite films for low-temperature processed high-efficiency solar cells

All-inorganic cesium lead halide perovskites (CsPbX ₃ ) have emerged as one of the most promising photovoltaic materials due to their superior thermal stability. However, the high phase transition temperatures (typically over 250 °C) of CsPbX ₃ perovskites are incompatible with flexible substrates. Herein, we employ a simple hot-casting method to fabricate low-temperature processed CsPbI ₂ Br films. By casting the perovskite precursor solution onto a hot substrate (maintained at 55 °C), compact, large-grain and pinhole-free CsPbI ₂ Br films can be prepared at a low post-annealing temperature, which outperform the conventional room temperature (RT)-casting and high-temperature (post-annealing at 340 °C) processed CsPbI ₂ Br films containing some voids. As a result, the hot-casting and low-temperature (post-annealing at 120 °C) processed CsPbI ₂ Br perovskite solar cells (PSCs) exhibited an outstanding power conversion efficiency (PCE) of 12.5%, which is much higher than that (2.91%) of the RT-casting processed CsPbI ₂ Br devices. Further optimization of the post-annealing temperature (optimized value: 180 °C) yielded the best performance of 13.8% for hot-casting processed CsPbI ₂ Br devices. This study gives an effective and facile strategy toward low-temperature processed all-inorganic perovskite films and high-performance PSCs.