Bandgap Engineering of Lead‐Free Double Perovskite Cs₂AgBiBr₆ through Trivalent Metal Alloying

The double perovskite family, AMMX, is a promising route to overcome the lead toxicity issue confronting the current photovoltaic (PV) standout, CHNHPbI. Given the generally large indirect band gap within most known double perovskites, band‐gap engineering provides an important approach for targeting outstanding PV performance within this family. Using CsAgBiBr as host, band‐gap engineering through alloying of In/Sb has been demonstrated in the current work. CsAg(BiM)Br (M=In, Sb) accommodates up to 75 % In with increased band gap, and up to 37.5 % Sb with reduced band gap; that is, enabling ca. 0.41 eV band gap modulation through introduction of the two metals, with smallest value of 1.86 eV for CsAg(BiSb)Br. Band structure calculations indicate that opposite band gap shift directions associated with Sb/In substitution arise from different atomic configurations for these atoms. Associated photoluminescence and environmental stability of the three‐metal systems are also assessed.

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Author David Mitzi Thomas Lord Department of Mechanical Engineering and Materia ...