Computational design of low-band-gap double perovskites

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Using density functional theory (DFT) based calculations, we propose a family of metastable, as-yet unmade V${}^{5+}$ and Cr${}^{6+}$ double perovskite compounds with low band gaps spanning much of the visible region of the solar spectrum. Through analysis of a related set of measured optical gaps of ${d}^{0}$ ABO${}_{3}$ perovskites and A${}_{2}$B${}^{\ensuremath{'}}$BO${}_{6}$ double perovskites, an ad hoc procedure is developed to correct DFT and many-body perturbation theory gaps, bringing them into quantitative agreement with experiment for measured compounds, and predicting that V${}^{5+}$ and Cr${}^{6+}$ double perovskites would have gaps ranging from approximately 1.1 to 2.4 eV, significantly lower than previous materials studied in this class. DFT calculations also establish that these V${}^{5+}$ and Cr${}^{6+}$ compounds are likely able to be synthesized, either in bulk form or as epitaxial thin films. These compounds would comprise a new class of semiconducting double perovskites for potential use in solar energy conversion and other optoelectronic applications.