Photoluminescence, photophysics, and photochemistry of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow><mml:msub><mml:mi mathvariant="normal">V</mml:mi><mml:mi mathvariant="normal">B</mml:mi></mml:msub></mml:mrow><mml:mo>−</mml:mo></mml:msup></mml:math> defect in hexagonal boron nitride
Jeffrey R. Reimers, Jun Shen, Mehran Kianinia, Carlo Bradac, Igor Aharonovich, Michael J. Ford, Piotr Piecuch
Abstract
Extensive photochemical and spectroscopic properties of the ${\mathrm{V}}_{\mathrm{B}}^{\ensuremath{-}}$ defect in hexagonal boron nitride are calculated, concluding that the observed photoemission associated with recently observed optically detected magnetic resonance is most likely of ${(1)}^{3}{E}^{\ensuremath{'}\ensuremath{'}}\ensuremath{\rightarrow}{(1)}^{3}{A}_{2}^{\ensuremath{'}}$ origin. Rapid intersystem crossing from the defect's triplet to singlet manifolds explains the observed short excited-state lifetime and very low quantum yield. New experimental results reveal smaller intrinsic spectral bandwidths than previously recognized, interpreted in terms of spectral narrowing and zero-phonon-line shifting induced by the Jahn-Teller effect. Different types of computational methods are applied to map out the complex triplet and singlet defect manifolds, including the doubly ionized formulation of the equation-of-motion coupled-cluster theory that is designed to deal with the open-shell nature of defect states, and mixed quantum-mechanics/molecular-mechanics schemes enabling 5763-atom simulations. Two other energetically feasible spectral assignments from among the singlet and triplet manifolds are considered, but ruled out based on inappropriate photochemical properties.