Defect-Induced Conical Intersections Promote Nonradiative Recombination.

We apply multireference electronic structure calculations to demonstrate the presence of conical intersections between the ground and the first excited electronic states of three silicon nanocrystals containing defects characteristic of the oxidized silicon surface. These intersections are accessible upon excitation at visible wavelengths and are predicted to facilitate nonradiative recombination with a rate that increases with decreasing particle size. This work illustrates a new framework for identifying defects responsible for nonradiative recombination.