Additive Effects of Guanidinium Iodide on CH3NH3PbI3Perovskite Solar Cells

CH3NH3PbI3(MAPbI3) perovskite solar cells with guanidinium (C(NH2)3+, GA+) are fabricated at 150 °C using 3CH3NH3I:PbCl2starting composition in ambient atmosphere, and characterized. Their photoconversion efficiencies and stabilities are improved by the addition of a small amount of GA+. Lattice volumes are increased by the addition of GA+, which confirms the occurrence of GA+substitution at the CH3NH3site. Energy gaps are decreased by the addition of GA+, which agrees well with the results of molecular orbital calculation and band calculation. The carrier trap density is reduced by the GA+addition, which suggests that lattice defects are suppressed by the GA+doping. Two‐year stabilities of the devices in ordinary air are also investigated, which indicate the effectiveness of GA addition. Photovoltaic properties of CH3NH3PbI3perovskite solar cells are improved by guanidinium (GA) addition. Lattice volumes are increased by the GA substitution at the CH3NH3site, which provides improvement of structures and electronic states, and the lattice defects of CH3NH3are also suppressed by the GA doping.