First-Principles Screening of Lead-Free Mixed-Anion Perovskites for Photovoltaics

摘要： Organic-inorganic hybrid lead perovskites have made rapid progress in photovoltaic fields. However, the toxicity and poor long-term stability of these materials still limit their further commercial application. Herein, we proposed a system of lead-free mixed-anion perovskites in which a chalcogen element is incorporated into the perovskite octahedrons to improve the system stability. We performed first-principles calculations of the bandgaps of 192 lead-free mixed-anion perovskites belonging to the class of ABX'X"2, where A=Cs+, CH3NH3+, and HC(NH2)2+; B=Ga3+, In3+, Sb3+, Bi3+; X'= O2-, S2-, Se2-, and Te2-, and X"= F-, Cl-, Br-, and I-. The bandgap shows a linear relationship with the average anion electronegativity. The contribution of anions to the band edge states is related to electron affinity and structure parameters. Considering multiple factors forming perovskites, we screened out a promising candidate, CsInOBr2, with a suitable bandgap (1.3 eV) for application in photovoltaics.