Compositional Engineering in α-CsPbI₃ toward the Efficiency and Stability Enhancement of All Inorganic Perovskite Solar Cells

Fully inorganic CsPbI3 has emerged to be a promising light-harvesting material compared to the organic/hybrid perovskites because of its excellent absorption properties in the visible regime. However, the optically active pure α-CsPbI3 phase is unstable at room temperature. In this work, we have employed a partial replacement strategy at the B-site of α-CsPbI3 and achieved long-term phase stability. A controlled partial substitution of Pb2+ cations by Sn2+ in the host lattice has enhanced the carrier lifetime and film quality of α-CsPbI3. The alloying of Sn2+ decreases the band gap, which leads to an upsurge in the short circuit current of the solar cell. The device based on Sn2+ alloyed α-CsPbI3 with an active cell area of 18 mm2 has shown a colossal photoconversion efficiency than the device based on unalloyed δ-CsPbI3. The champion cell also maintained 78% of its primary efficiency after 15 days in a circumjacent atmosphere. This work brings out the optimal alloying amount of Sn for better stability and maximum device output.