Rational design of bismuth-based oxide double-perovskite semiconductors with large band-gap tunability*

Bismuth-based halide double perovskites, such as Cs₂AgBiBr₆, have emerged as a new class of semiconductors with applications in solar-energy harvesting and optoelectronics. However, these halides suffer from long-term stability issues due to the weak metal-halogen bonds. We have explored Bi-based oxide double perovskites as an alternative class of semiconducting materials. The oxide framework improves stability due to stronger metal-oxygen bonds and the -2 charge of the oxide anion opens a vast cation composition space to tune the electronic structure of the material. We use a combination of high-throughput density-functional-theory calculations and machine learning to screen through the vast composition space of over 29,000 A'A"M'BiO₆ hypothetical oxide double perovskites. We predict various stable compounds within the A'A"M'BiO₆ composition space, where M' = V, Mo, W, Ta, Nb, Sb,and Te, which can find applications as stand-alone absorbers, absorbers in tandem solar cells and as photocatalysts.