Metropolis Dissertation Award Winner: Nonradiative Transitions at Defects in Solids

Point defects and impurities in solids provide a means for carriers to recombine nonradiatively, which has important implications for the performance of electronic devices. These nonradiative transitions are driven by the electron-phonon interaction, where excess energy is given to lattice vibrations. First-principles calculations are a powerful tool to assess and predict the impact of defect-mediated nonradiative recombination. I will discuss the development of and recent improvements to the Nonrad code, which implements a first-principles formalism to evaluate the nonradiative transition rate. I will then overview several examples of its application to solve outstanding research problems. In hexagonal boron nitride, single-photon emitters have been observed, which are promising for applications in quantum information science. I will describe how nonradiative transitions can help to rationalize the optical dynamics of these emitters and suggest that the microscopic origin of the emission is a boron dangling bond. Halide perovskite solar cells have achieved remarkable efficiencies, but defect-mediated nonradiative recombination still poses a problem. I will discuss how our studies of nonradiative recombination in the perovskites provide potential routes for improving device efficiency.

Work performed in collaboration with A. Alkauskas, X. Zhang, M. Engel, G. Kresse, D. Wickramaratne, J.-X. Shen, C. E. Dreyer, R. N. Patel, J. A. Gusdorff, L. C. Bassett, and C. G. Van de Walle.