Quantitative experimental assessment of hot carrier-enhanced solar cells at room temperature

In common photovoltaic devices, the part of the incident energy above the absorption threshold quickly ends up as heat, which limits their maximum achievable efficiency to far below the thermodynamic limit for solar energy conversion. Conversely, the conversion of the excess kinetic energy of the photogenerated carriers into additional free energy would be sufficient to approach the thermodynamic limit. This is the principle of hot carrier devices. Unfortunately, such device operation in conditions relevant for utilization has never been evidenced. Here, we show that the quantitative thermodynamic study of the hot carrier population, with luminance measurements, allows us to discuss the hot carrier contribution to the solar cell performance. We demonstrate that the voltage and current can be enhanced in a semiconductor heterostructure due to the presence of the hot carrier population in a single InGaAsP quantum well at room temperature. These experimental results substantiate the potential of increasing photovoltaic performances in the hot carrier regime. Hot carrier solar cells promise efficiencies above the thermodynamic limit but the hot carrier effects remain elusive so far. Here, Nguyen and Lombez et al. quantify the hot carrier contribution to the voltage and current of a micrometre-scale solar cell operating at room temperature, with an efficiency up to ~11%.