Lead free perovskites have drawn considerable attention in last few years. Tin (Sn) have potential to replace lead (Pb), however Sn4+ caused by oxidation of Sn deteriorates the solar cell performance. In this article, we have presented the design and fabrication of FASnI3 solar cell and analyze the impact of various parameters on the efficiency of cell module. In addition, we have used solvent engineering with SnF2 as a blockage of Sn4+. We have achieved 6.01% efficiency with fabricated device using FASnI3 as an active layer. Furthermore, the roles of the defect, interface, contact work function, and charge selecting layer on the efficiency of device have been rigorously investigated. With optimized process parameters, the device efficiency can be further improved up to 18.76%