Hot phonon bottlenecks and the role of non-equilibrium acoustic phonons in III–V multi-quantum well systems

The hot phonon bottleneck effect is a promising mechanism for the realization of a true hot carrier solar cell. Prior work has assumed that the acoustic phonons created via the decay of longitudinal polar optical (LO) phonons are assumed to quickly leave the system or thermalize quickly due to multi-phonon processes. We expand upon previous work to include a build-up of longitudinal acoustic phonons in addition to LO phonons due to the Klemens process. By including this additional process, unphysical assumptions concerning the LO anharmonic lifetime are no longer required, resulting in a better explanation of the experimental results, and pointing toward potential alternative approaches for achieving high carrier temperatures during photo-excitation.