Perovskite solutions that were doped with potassium (K) salts (CH3NH3)(0.8)(HC(NH2)(2))(0.1)K0.1PbI3 (MA(0.8)FA(0.1)K(0.1)PbI(3)(Cl)) were used to fabricate perovskite solar cells. The addition of the K salts resulted in fine grained perovskite crystals that were separated by very small gaps. These materials were used to fabricate solar cells that improved short circuit current densities, which resulted in an enhanced conversion efficiency, compared with standard materials. The K occupied the (CH3NH3)/(HC(NH2) defects within the perovskite crystals, which caused the lattice constant to increase. Additionally, the presence of K in the perovskite solutions promoted the growth of grains within the perovskite crystals.