The efficiency of Sn-perovskite solar (Sn-PVK) cells was enhanced by adding 1% Samarium iodide (SmI2). Increase in J(sc) and FF is associated with the enhancement of efficiency and and explained by lower series resistance. SmI2 is known as a strong reducing agent and is oxidized to Sm3+ by reducing a substrate. By adding 1 and 5% SmI2, the carrier concentration of Sn-perovskite layer due to the presence of Sn4+ was decreased from 4.8 x 10(22)/cm(3) to 1.2 x 10(19)/cm(3) and 6.1 x 10(18)/cm(3) respectively, because of the suppression of the oxidation from Sn2+ to Sn4+ by the strong reducing properties of SmI2. The low charge carrier concentration is also associated with the enhanced solar cell efficiency.