Fabrication and characterization of potassium- and formamidinium-added perovskite solar cells

Abstract

Perovskite solutions with potassium (K) and formamidinium (FA) iodides added were used to fabricate perovskite solar cells. Since the lattice constants increased with the addition of FA, the substitution by FA of the CH₃NH₃ (MA) site of the perovskite crystal was confirmed. In addition, conversion efficiencies were improved for devices with K and FA added compared with standard devices. The presence of K in the perovskite solution promoted formation of highly (002)-oriented crystals, which decreased the lattice strain of perovskite crystals. Filling the MA defect sites with K and FA can prevent the recombination of electrons and holes and improve the photovoltaic characteristics.