  Point defects in hexagonal boron nitride (hBN) have attracted growing
attention as bright single-photon emitters. However, understanding of their
atomic structure and radiative properties remains incomplete. Here we study the
excited states and radiative lifetimes of over 20 native defects and carbon or
oxygen impurities in hBN using ab initio density functional theory and GW plus
Bethe-Salpeter equation calculations, generating a large data set of their
emission energy, polarization and lifetime. We find a wide variability across
quantum emitters, with exciton energies ranging from 0.3 to 4 eV and radiative
lifetimes from ns to ms for different defect structures. Through a Bayesian
statistical analysis, we identify various high-likelihood defect emitters,
among which the native $\mathrm{V_NN_B}$ defect is predicted to possess
emission energy and radiative lifetime in agreement with experiments. Our work
advances the microscopic understanding of hBN single-photon emitters and
introduces a computational framework to characterize and identify quantum
emitters in 2D materials.
