Incorporation of γ-aminobutyric acid and cesium cations to formamidinium lead halide perovskites for highly efficient solar cells

Abstract The stability issue has become one of the main challenges for the commercialization of perovskite solar cells (PSCs). Formamidinium (FA)-based perovskites have shown great promise owing to their improved thermal and moisture stability. However, these perovskites are suffering from phase transition and separation. Here, a method of incorporating of γ-aminobutyric acid (GABA) and cesium cations into FAPbI3 is developed to improve the phase stability. It is demonstrated that the crystallinity of α-FAPbI3 phase is greatly improved and the phase transition temperature is significantly dropped. The resultant solar cell therefore obtains a champion power conversion efficiency (PCE) of 23.71%, which is one of the highest efficiencies for methylammonium-free PSCs. Furthermore, it shows an impressively enhanced stability under illumination, exhibiting the great potential of FA-based perovskites for efficient and stable solar cells.