Applicability of quasi-equilibrium models to advanced photovoltaic concepts

Solar energy conversion is a nonequilibrium process in which high temperature light is converted into low temperature electrical power. Yet, photovoltaic cells are usually treated in an equilibrium thermodynamics formalism, assuming quasi-equilibrium electron distributions. I will unravel how different timescales of interaction determine the applicability of quasi-equilibrium models in the photovoltaic concepts of multi-exciton generation, hot carrier, and intermediate band solar cells. In hot carrier solar cells, the sparsity of the solar flux plays a key role in establishing quasi-equilibrium, making the local density of optical states a critical parameter for enabling high efficiencies.