Pb free perovskite solar cells with over 13 % efficiency-Direction to high efficiency-Pb free solar cells-

This is a report on Pb free perovskite solar cells. Direction to enhancing efficiency for Sn-perovskite solar cells are discussed. In order to decrease carrier density and defect density in Sn-perovskite layers, Ge ion doping, surface and grain boundary passivation, decrease in lattice strain, and band alignment are proved to be effective. Ge doped Sn-perovskite solar cells with 13% efficiency is reported.