Design rules for optimizing quaternary mixed-metal chalcohalides

Quaternary mixed-metal chalcohalides (M(II)${}_{2}$M(III)Ch${}_{2}$X${}_{3}$) combine the beneficial optoelectronic properties of halide perovskites with the stability of chalcogenides, making them as promising photovoltaic absorbers. By integrating density functional theory with random forest regression and Shapley additive explanations, the authors identified compositional trends and design rules across 54 lead-free and lead-containing compounds. The results reveal that electron acceptor sites (Ch and X) are crucial in shaping overall material behaviour, while donor sites (M(II) and M(III)) enable targeted tuning of properties for specific applications. These insights provide guidelines for designing mixed-metal chalcohalides for photovoltaic and optoelectronic applications.