First-principles studies of oxygen defects in h-BN as near-infrared single-photon emitters

Hexagonal boron nitride (h-BN) is a promising host for quantum light sources, owing to its wide bandgap (~6 eV), chemical stability, and two-dimensional nature that facilitates photon extraction and device integration. Single-photon emitters (SPEs) have been observed in h-BN from ultraviolet to near-infrared, but in many cases the defect origin remains unknown. Recent experiments revealed oxygen-related SPEs with sharp zero-phonon lines (ZPLs) at 770 nm and 856 nm under 660 nm and 765 nm excitation [1], featuring ultranarrow cryogenic linewidths, high Debye–Waller factors, and uncommon red shift. Motivated by these findings, we perform hybrid density functional theory to investigate oxygen-related defects in h-BN, focusing on their potential as quantum emitters. Our calculations identify two oxygen complexes whose electronic structures and optical transitions reproduce the observed ZPLs and explain the microscopic origin of red shift. This study establishes oxygen-related complexes as an important class of SPEs in h-BN and highlights their prospects for scalable integration into quantum photonics.