Ultrahigh-efficiency and robust thermophotovoltaic devices via spectral-heat filtering

Thermophotovoltaics (TPVs) are solid-state photonic heat engines that convert thermal radiation into continuous power generation through photovoltaics. Recent work on photon recuperation using back-surface reflectors has remarkably boosted TPV efficiencies. However, building a practical TPV device with photons actually recuperated remains a challenge because of the strong emitter-cell thermal coupling. Here we build a robust TPV device through emitter-side photon recuperation using a spectral-heat filter (SHF). The SHF, optimized via multi-objective machine learning, blocks 99% of the sub-bandgap radiation as well as the thermal conduction and convection from the emitter. The accelerated thermal ageing test shows the fabricated SHF has a L70-rated lifetime of 57,477 hours. The emitter-SHF pair decouples the temperature-susceptible PV cell from the photon-recuperation process, and unlocks the mass-produced state-of-the-art photovoltaic cells for use in TPV. The emitter-SHF pair engineers the above-bandgap radiation to achieve current matching in the GaInP/GaAs/Ge triple-junction photovoltaic cell. The efficiency of the TPV device reaches 47.16% ± 1.12% at the emitter temperature of 2,162 °C. The spectral-heat filtering architecture offers inherent operational robustness as well as the power conversion efficiency surpassing conventional heat engines.