Orientation Regulation of Tin-Based Reduced-Dimensional Perovskites for Highly Efficient and Stable Photovoltaics

Tin-based perovskites have exhibited high potential for efficient photovoltaics application due to their outstanding optoelectrical properties. However, the extremely undesired instabilities significantly hinders their development and further commercialization process. A novel tin-based reduced-dimensional (quasi-2D) perovskites is reported here by using 5-ammoniumvaleric acid (5-AVA⁺) as the organic spacer. It is demonstrated that by introducing appropriate amount of ammonium chloride (NH₄Cl) as additive, highly vertically oriented tin-based quasi-2D perovskite films are obtained, which is proved through the grazing incidence wide-angle X-ray scattering characterization. In particular, this approach is confirmed to be a universal method to deliver highly vertically oriented tin-based quasi-2D perovskites with various spacers. The highly ordered vertically oriented perovskite films significantly improve the charge collection efficiency between two electrodes. With the optimized NH₄Cl concentration, the solar cells employing quasi-2D perovskite, AVA₂FA_{n −1}Sn_nI_{3 n +1} (<n> = 5), as light absorbers deliver a power conversion efficiency up to 8.71%. The work paves the way for further employing highly vertically oriented tin-based quasi-2D perovskite films for highly efficient and stable photovoltaics.