Photoluminescence and Electron-hole Recombination of Defects as Single Photon Emitters in Hexagonal Boron Nitride

To unambiguously identify defects responsible for the experimentally detected single-photon emissions in hexagonal boron nitride, we theoretically investigate the photoluminescence and electron-hole recombination mechanism (radiative and nonradiative) of defect candidates, especially carbon related defects. The slow supercell convergence of electron-phonon coupling impacts the accuracy of photoluminescence and nonradiative recombination rates. We found the low energy bulk state modes are the main cause for this slow convergence, and provided possible solutions. Furthermore, optical excitation including defect-exciton coupling is computed by solving the Bethe-Salpeter equation. We found large variation of exciton binding energy and radiative lifetime among different defects. At the end, the layer dependence and strain effects on photoluminescence and electron-hole recombination properties will also be discussed to help to unequivocally identify sources of single photon emission.