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.
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