LAUSR

Perovskite solar cells based on the lead free hybrid organic–inorganic CH3NH3SnI3 (MASnI3) and CH4N2SnI3 (FASnI3) perovskites were fabricated, and the photoelectric conversion efficiency (PCE) was assessed. FASnI3's PCE was higher than MASnI3's efficiency. To study the different photovoltaic properties, we calculated their structural, electronic, and optical properties using density functional theory via the Perdew–Burke–Ernzerhof and spin–orbit coupling (PBE-SOC) methods. The results show that FASnI3 exhibits an appropriate band gap, substantial stability, marked optical properties, and significant hole and electron conductive behavior compared with MASnI3. The interaction of organic cations (FA+) with the inorganic framework of FASnI3 was stronger than that with MASnI3, so they affected the band length and band angle distribution, causing the structure of the FASnI3 and MASnI3 to change. The calculations also demonstrated that energy splitting was evident in FASnI3 due to the spin–orbit coupling effect, however, it was moderate in MASnI3, which was caused by the H bond effect. This research not only furthers the understanding of these functional materials, but also can assist the development of highly efficient and stable non-lead perovskite solar cells.