Dimension engineering on cesium lead iodide for efficient and stable perovskite solar cells

Abstract

Cesium lead iodide perovskite (CsPbI₃) has been proposed as an efficient alternative to modify the instability of methylammonium lead iodide (MAPbI₃) under thermal and humidity stress. However, three-dimensional (3D) cesium lead iodide forms an undesirable non-perovskite structure with a wide bandgap at ambient atmosphere. Herein, dimension engineering is employed by introducing a bulky ammonium cation to form stable 2D cesium lead iodide perovskite BA₂CsPb₂I₇ (BA = CH₃(CH₂)₃NH₃), which not only exhibits prominent optoelectronic properties, but also possesses superior structural and compositional stability to 3D CsPbI₃ and MAPbI₃ under the pressure of heat and humidity. The current 2D BA₂CsPb₂I₇ shows excellent stability after exposure to 30% relative humidity for 30 days or upon heating at 85 °C for 3 days. In addition, the corresponding BA₂CsPb₂I₇ based planar perovskite solar cells retain 92% of the initial power conversion efficiency (PCE) after aging for over 30 days without any encapsulation, demonstrating the up-scalability of 2D perovskite compounds as stable and efficient light-absorbing materials for perovskite solar cells and other optoelectronic applications.