Ambient stable FAPbI3-based perovskite solar cells with a 2D-EDAPbI4 thin capping layer

Two-dimensional (2D) lead halide perovskite materials are emerging as one of promising light-absorbing materials in perovskite solar cells (PSCs), which show outstanding stability and defect passivation. Unfortunately, the power conversion efficiency (PCE) of those stable 2D PSCs is still far behind that of 3D PSCs. Herein, we reported a simple in-situ growth technique for the ethylenediamine lead iodide (EDAPbI4) layer on the top of formamidinium lead iodide (FAPbI3) layer. The rationally designed layered architecture of 2D-3D perovskite film could improve the PCE of the PSCs. In addition, benefiting from the high moisture resistance and inhibited ion migration of EDAPbI4 layer, the 2D-3D-based devices showed obviously enhanced long-term stability, keeping the initial PCE value for 200 h and 90% of its initial PCE even after 500 h.