Designing indirect-direct bandgap transitions in double perovskites

A general design strategy is presented for tuning the convergence of direct and indirect bandgaps based on chemical adjustment of the s- and p-orbital character of the conduction band minimum. To demonstrate the viability of the design strategy, we successfully synthesized a family of double perovskites: Cs2AgSbCl6 with an indirect bandgap and Cs2AgInCl6 with a direct bandgap and the solid solutions between the two.