Efficient inverted planar formamidinium lead iodide perovskite solar cells a post improved perovskite layer

Formamidinium lead iodide (FAPbI 3 ) is a more promising broader absorption material than methylammonium lead iodide (MAPbI 3 ) for perovskite solar cells (PSCs). However, in most cases the power conversion efficiencies (PCE) of FAPbI 3 based inverted planar PSCs are still lower than those of MAPbI 3 ones due to the inferior morphology of FAPbI 3 film. In this paper, we demonstrate an optimised formamidinium iodide/isopropyl alcohol (FAI/IPA) modification procedure to improve the photoactive layer for efficient inverted planar FAPbI 3 PSCs. The results show that there is an obvious improvement in open circuit voltage, short current density ( J SC ), and fill factor (FF). Finally, the best PCE of 14.00% with a J SC of 21.75 mA cm −2 and a FF of 0.78 was achieved in low-temperature solution-processed PSCs, which represents a more than 40% enhancement in PCE over that of the PSCs without surface modification. Moreover, the devices exhibit good reproducibility and excellent stability. The simple FAI/IPA modification on the photoactive layer can greatly improve planar FAPbI 3 based device performance, which can be a good choice for practical applications. In this paper, we demonstrate an optimised formamidinium iodide/isopropyl alcohol (FAI/IPA) modification procedure to improve the photoactive layer for efficient inverted planar FAPbI 3 PSCs.