Systematic Band Gap Tuning of BaSnO₃ via Chemical Substitutions: The Role of Clustering in Mixed-Valence Perovskites

By combining high-throughput experiments and first-principles calculations based on the DFT-ACBN0 approach, we have investigated the energy band gap of Sr-, Pb-, and Bi-substituted BaSnO₃ over wide concentration ranges. We show that the band gap energy can be tuned from 3 to 4 eV by chemical substitution. Our work indicates the importance of considering the mixed-valence nature and clustering effects upon substitution of BaSnO₃ with Pb and Bi. Starting from the band gap of ∼3.4 eV for pure BaSnO₃, we find that Pb substitution changes the gap in a nonmonotonic fashion, reducing it by as much as 0.3 eV. Bi substitution provides a monotonic reduction but introduces electronic states into the energy gap due to Bi clustering. Our findings provide new insight into the ubiquitous phenomena of chemical substitutions in perovskite semiconductors with mixed-valence cations that underpin their physical properties