Photovoltaic Performance of Lead-Less Hybrid Perovskites from Theoretical Study

In recent years, organic–inorganic hybrid halide perovskites have attracted great attention. In view of the toxicity of lead, lead-free perovskites have been developed in order to obtain comparable or better photovoltaic performance than MAPbI3. In this study, the structural, electronic, and optical properties of pure and mixed perovskite systems were investigated by using density functional theory calculations. The results reveal that three Pb–Sn–Ge perovskites are predicted to preserve improved structural stabilities over MAPbI3. The band gaps of hybrid perovskites can be tuned by means of Sn–Ge doping. The band gap of MAPb0.50Sn0.25Ge0.25I3 is in the optimum range of 1.3–1.4 eV. Optical property analysis implies that MAPb0.50Sn0.25Ge0.25I3 possesses a comparable absorption ability in the visible light region compared with the MAPbI3 structure. In addition, the results indicate that MAPb0.50Sn0.25Ge0.25I3 with the highest power conversion efficieny of 23.65% can be chosen as a potential candidate for the light absorption layer. The amount of lead will decline to a certain extent because of the partial substitution of Pb by Sn and Ge. These results are expected to be helpful for further experiments to find new kinds of possible lead-less or lead-free perovskite materials.