Phonon lifetimes in model quantum dot superlattice systems with applications to the hot carrier solar cell

The lifetime of high energy phonons in a QD superlattice is computed for plausible model materials from Time Dependent Perturbation Theory (TDPT). Klemens decay can be inhibited for a range of high energy phonons if a significant phonon bandgap exists. Ridley-type decays can compete with Klemens for speed due to the large density of states available for decay products on some decay paths and are typically a few picoseconds. In diamond superlattices where QDs occupy the majority of the unit cell, computed lifetimes can be as long as hundreds of picoseconds for certain symmetry directions.