Metal-halide perovskites with superior photophysical properties and low-cost solution process have emerged as promising candidates for different optoelectronic devices, including solar cells, light-emitting diodes, etc . For perovskite solar cells (PSCs), different compositions have been attempted for high efficiencies. Among others, formamidinium lead iodide (FAPbI3) have promised great potential, due to their optimal band-gap of ~1.5 eV and excellent thermal stability .