Alloying to tune the bandgap of the <i>AM</i> ₂ <i>Pn</i> ₂ Zintl compounds

Abstract The AM 2 Pn 2 Zintl compounds are a large class of semiconductor materials that have a wide range of bandgaps and are mostly stable in the same crystal structure. Representative compounds BaCd 2 P 2 and CaZn 2 P 2 have recently been found to exhibit high visible light absorption and long carrier lifetime. Here we use high throughput first-principles calculations to study AM 2 Pn 2 alloys for applications as tandem top cell absorbers (i.e. bandgaps around 1.8 eV) and far infrared (IR) detector materials (i.e. bandgaps lower than 0.5 eV). Using a first-principles computational screening workflow for assessing stability and electronic structure of alloys, we identify several promising candidates. These include Ca(Cd 0.8 Mg 0.2 ) 2 P 2 with a suitable direct bandgap for use in tandem top cells on silicon bottom cells and SrCd 2 (Sb 1− x Bi x ) 2 for far IR detectors. We demonstrate that alloys of AM 2 Pn 2 materials can be realized by experimentally synthesizing Ca(Zn 0.8 Mg 0.2 )2P 2 .