Long photoexcited carrier lifetime in a stable and earth-abundant zinc polyphosphide
Halide perovskites have revolutionized optoelectronics by demonstrating that long carrier lifetime can be achieved in materials processed in relatively uncontrolled environments, whereas conventional inorganic semiconductors typically suffer from short carrier lifetime unless very carefully prepared and postprocessed. Here, we report the discovery of exceptionally long photoexcited carrier lifetime in monoclinic ZnP2, effectively bridging the carrier lifetime gap between direct-gap inorganic semiconductors and halide perovskites. Through computational screening, ZnP2 is identified as a long carrier lifetime semiconductor characterized by an unconventional polyphosphide bonding, combining covalently bonded phosphorus chains and polar-covalent Zn-P tetrahedra. Experimentally, ZnP2 crystals synthesized from low-purity precursors exhibit bright band-to-band photoluminescence at 1.49 eV and carrier lifetimes of up to 1 $\mu$s. Further analysis reveals that the polyphosphide bonding of ZnP2 suppresses the formation of deep intrinsic defects, making it defect resistant. Combined with its remarkable environmental stability, ZnP2 presents a highly promising material for solar absorbers and light emitters. Our work illustrates that underexplored inorganic materials spaces with unusual chemical bonding hold great promise for discovering novel optoelectronic materials.