Hot electrons and cold holes: operation, efficiency, and design of a two-temperature hot-carrier solar cell

Hot-carrier solar cells (HCSCs) offer the potential to enhance the energy-conversion efficiency of photovoltaic devices up to 86%. However, most HCSC models to date assume that electrons and holes have the same temperature, whereas many reports in III to V materials indicate that electrons can be much hotter than their counterparts. We present a detailed balance HCSC model that includes different temperatures for electrons and holes. We focus on the impact of the temperature imbalance on the voltage of such an HCSC and its power-conversion efficiency. Surprisingly, a temperature imbalance at a fixed effective temperature leads to a slight power-conversion efficiency increase, up to 1 to 2 percentage points, primarily due to an increase in fill factor and possibly open-circuit voltage. Yet, we show that the knowledge of the effective temperature alone is sufficient to design a satisfying HCSC.