Low Temperature Fabrication for High Performance Flexible CsPbI 2 Br Perovskite Solar Cells

摘要

All‐inorganic CsPbX 3 ‐based perovskites, such as CsPbI 2 Br, show much better thermal and illumination stability than their organic–inorganic hybrid counterparts. However, fabrication of high‐quality CsPbI 2 Br perovskite film normally requires annealing at a high temperature (250 °C) that is not compatible with the plastic substrate. In this work, a Lewis base adduct‐promoted growth process that makes it possible to fabricate high quality CsPbI 2 Br perovskite films at low temperature is promoted. The mechanism is attributed to synthesized dimethyl sulfoxide (DMSO) adducts which allow a low activation energy route to form CsPbI 2 Br perovskite films during the thermal annealing treatment. A power conversion efficiency (PCE) of 13.54% is achieved. As far as it is known, this is the highest efficiency for the CsPbI 2 Br solar cells fabricated at low temperature (120 °C). In addition, the method enables fabrication of flexible CsPbI 2 Br PSCs with PCE as high as 11.73%. Surprisingly, the bare devices without any encapsulation maintain 70% of their original PCEs after being stored in ambient air for 700 h. This work provides an approach for preparing other high performance CsPbX 3 ‐based perovskite solar cells (PSCs) at low temperature, particularly for flexible ones.