Photovoltaic characteristics of solar cell devices in which ethylammonium (EA) and formamidinium (FA) were added to CH3NH3PbI3 perovskite photoactive layers were investigated. The thin films for the devices were deposited by an ordinary spin-coating technique in ambient air, and the X-ray diffraction analysis revealed changes of the lattice constants, crystallite sizes and crystal orientations. By adding FA and EA, surface defects of the perovskite layer decreased, and the photoelectric parameters were improved. In addition, the highly (100) crystal orientations and device stabilities were improved by the EA and FA addition.

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 CH 3 NH 3 (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.

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CH 3 NH 3 PbI 3¹x Cl x -based photovoltaic devices with guanidinium [C(NH 2 ) 3 , GA] were fabricated and characterized. The additive effects of guanidinium iodide, formamidinium [CH(NH 2 ) 2 , FA] iodide, and guanidinium chloride were compared. Short-circuit current densities, open-circuit voltages, series resistances and shunt resistances were improved by the GA addition. The short-circuit current densities were increased by FA addition with GA. The incident photon-to-current conversion efficiency increased, which results from the suppression of pin-holes in perovskite layers by GA addition. The conversion efficiencies were improved by GA addition. X-ray diffraction showed that the lattice constants of the perovskite crystals increased by GA and FA addition, and that the GA substituted partially at the CH 3 NH 3 -site.

Additive effects of guanidinium [C(NH2)3, GA] iodide, formamidinium [CH(NH2)2, FA] iodide, and guanidinium chloride to CH3NH3PbI3-based photovoltaic devices were investigated. Short-circuit current densities, open-circuit voltages, series resistances and shunt resistances were improved by the GA addition. The short-circuit current densities were increased by FA addition with GA, and the external quantum efficiencies increased, which resulted in suppression of pinholes in perovskite layers by the GA addition. X-ray diffraction showed that the lattice constants of the perovskite crystals increased by the GA and FA addition, and that the GA substituted partially at the CH3NH3-site.