46772-AC6
Time-domain Ab Initio Studies of Relaxation Dynamics of Photogenerated Carriers in Quantum Dot Solar Cells
Spatial confinement can create relaxation bottlenecks by mismatch between electronic and vibrational frequencies. This hypothesis motivated discovery of multiple excitons, which could greatly enhance quantum dot (QD) solar cells. Surprisingly, recent experiments showed no bottleneck. We performed time-domain ab initio study of the electron-phonon dynamics rationalizes the fast relaxation in PbSe and CdSe QDs, which have substantially different electronic properties. Atom fluctuations and surface effects lift degeneracies and create dense distributions of electronic levels at all but the lowest energies, while confinement enhances the electron-phonon coupling. The analysis applies to nanomaterials in general, modifying the fundamental view on the electron-phonon interaction.
