Novel solar absorbers from phosphides: BaCd₂P₂ and more

With InP and GaP as notable examples, phosphide compounds present exciting opportunities for discovering new solar absorbers. We demonstrate this with the ternary Zintl phosphide BaCd₂P₂, a novel candidate identified from our high-throughput computational screening for stable and long carrier lifetime solar absorbers. Our extensive theoretical and experimental evidence shows that BaCd₂P₂ is highly stable and exhibits excellent optoelectronic and defect properties, including shallow low-energy intrinsic defects, bright photoluminescence, and a carrier lifetime of up to 30 ns, even in powder form. These promising properties extend to all AM₂P₂ (A=Ca, Sr, Ba, M=Zn, Cd) Zintl phosphides, which, with tunable band gaps (~1.5–2.0 eV), form a class of defect-tolerant solar absorbers suitable for both single-junction and tandem solar cells. Additionally, we will discuss our recent focused computational screening of nearly all known phosphides, which has led to a defect database for phosphides. Some interesting candidates will be presented, and, based on our data on phosphides across various structure types and chemistries, we will provide insights into the relationship between a material’s electronic structure and its defect tolerance.