Electronic Structure and Stability of Lead-free Hybrid Halide Perovskites: A Density Functional Theory Study

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The most commonly used and studied hybrid halide perovskite is ABX3, where A usually stands for CH3NH3, B for Pb, and X for I. A lead-free perovskite with high stability and ideal electronic band structure would be of essence, especially considering the toxicity of lead. In this work, we have considered 11 metal elements for the B site and three halide elements (Cl, Br, and I) including various combinations among the three halides for the X site. A total number of 99 hybrid perovskites are studied to understand how the crystal structure, band gap and stability can be tuned by the chemistry modification, i.e., the replacement of toxic element, Pb in the original MAPbX3, with non-toxic metal elements. We find that the favorable substitutes for Pb in MAPbI3 are Ge and Sn.