BaCd2P2: a promising impurity-tolerant counterpart of GaAs for photovoltaics

BaCd2P2 (BCP) has been recently identified as a new solar absorber with promising optoelectronic properties. This work demonstrates that, despite having a low precursor purity (98.90% to 99.95%), synthesized BCP samples exhibit a promising photoconductive carrier lifetime up to 300 ns, an implied open-circuit voltage exceeding 1 V, and photoluminescence quantum yield in the order of 0.2%, comparable to a high-purity single-crystalline GaAs wafer. To better understand the underlying mechanisms of BCP's promising properties, its tolerance to intrinsic defects and extrinsic impurities is investigated using first-principles defect modeling and compared with that of the well-studied GaAs. The results show that the nonradiative recombination rates induced by dominant deep-level intrinsic antisite defects are lower in BCP than in GaAs under typical growth conditions. Further exploration of the impact of transition metal impurities in the raw materials used to make BCP and impurities introduced during its synthesis shows that most of these do not form deep-level nonradiative recombination centers. As an impurity-tolerant counterpart of GaAs, BCP demonstrates great potential to improve the cost-to-performance ratio of photovoltaics.