Phosphosulfides with P/S > 1. To the best of our knowledge, PSs with a P/S ratio above 1 have never been synthesized and are rarely present in computational materials databases. The only such material available on MP seems to be Zr 2 P 3 S. Nevertheless, a 2019 computational screening study by Amsler et al. based on density functional theory (DFT) included four PSs with P/S = 2 in their pool of candidates (Mg 4 P 2 S, Ca 4 P 2 S, Sr 4 P 2 S, and Ba 4 P 2 S). Unexpectedly, the authors found all these compounds except for Mg 4 P 2 S to be thermodynamically stable in a previously unknown crystal structure derived from the Ba 3 As 2 structure. The implications of this recent discovery on optoelectronic energy conversion applications will be discussed later. At this stage, we simply note that the results by Amsler et al. suggest that a large portion of the PS material space (i.e., compounds with P/S > 1) may still be awaiting discovery.