Iron-Chalcogenide Based Solar Absorbers*

Earth abundant, non-toxic solar absorbers are greatly desirable to reduce solar cell production cost. FeS$_{2}$ pyrite, with a band gap of $\sim $0.9 eV, is well known for outstanding absorption properties, yet significant photoconversion has never been achieved. Our computational and experimental study recognizes the failure mechanism of iron pyrite as an instability with respect to other Fe$_{x}$S (0.5$<$x$\le $1) metallic compositions. A set of design rules emerges for the realization of high absorption transition metal-chalcogenide absorbers. Fe$_{2}$MS$_{4}$ (M=Si,Ge) are proposed as viable candidates, and merit for solar absorber application discussed.