Bication lead iodide 2D perovskite component to stabilize inorganic α-CsPbI3 perovskite phase for high-efficiency solar cells

Among various all-inorganic halide perovskites exhibiting better stability than organic-inorganic halide perovskites, alpha-CsPbI3 with the most suitable band gap for tandem solar cell application faces an issue of phase instability under ambient conditions. We discovered that a small amount of two-dimensional (2D) EDAPbI(4) perovskite containing the ethylenediamine (EDA) cation stabilizes the alpha-CsPbI3 to avoid the undesirable formation of the nonperovskite delta phase. Moreover, not only the 2D perovskite of EDAPbI(4) facilitate the formation of alpha-CsPbI3 perovskite films exhibiting high phase stability at room temperature for months and at 100 degrees C for > 150 hours but also the alpha-CsPbI3 perovskite solar cells (PSCs) display highly reproducible efficiency of 11.8%, a record for all-inorganic lead halide PSCs. Therefore, using the bication EDA presents a novel and promising strategy to design all-inorganic lead halide PSCs with high performance and reliability.