Recently, we used statistical learning to systematically identify a new tolerance factor, τ, that predicts the stability of single and double perovskite oxides and halides with much higher quantitative accuracy than Goldschmidt’s famous tolerance factor, t. As with Goldschmidt’s tolerance factor, τ is one-dimensional, requiring only the chemical formula to generate a prediction of perovskite stability. The functional form of τ reveals new physical insights into the stability of perovskite structures and allows the high-throughput screening of perovskite stability with improved accuracy (e.g., less false positives) compared with previous descriptors. We use τ to predict the stability of &gt; 500,000 double perovskites, of which ~350 are predicted to be stable with A = Cs and X = Cl – a class of double perovskites that have gained much attention as lead-free solar absorbers. For each of these ~350 materials, we predict thermodynamic stability with respect to competing compounds (likely precursors) using quaternary phase diagrams calculated with density functional theory (DFT) and, in particular, the meta-GGA functional, SCAN. This analysis reveals ~100 Cs2BB’Cl6 materials that are stable against decomposition and have SCAN-calculated band gaps that might be attractive for absorption in the visible spectrum. To validate the optical properties of these select Cs2BB’Cl6 candidates, we re-calculated the electronic structure using the hybrid HSE06 functional. For 10 candidates that have direct or nearly-direct HSE06 band gaps between 1 and 2 eV, we perform a detailed optical characterization, which includes self-consistent geometry optimization and calculation of absorption spectra with HSE06. In addition to revealing promising all-inorganic cesium chloride double perovskite solar absorbers, we also show the importance of considering perovskite decomposition into likely precursors (rather than using formation enthalpies) to predict perovskite stability, as well as low-symmetry structural distortions, which significantly alters the calculated optical properties of double perovskites.

Computational identification of all-inorganic cesium chloride double perovskite solar absorbers

2019 Spring National Meeting

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