Thermophotovoltaic (TPV) cells utilize locally emitted thermal radiation to generate electricity. To reach high efficiencies, the unusable spectrum (the below bandgap, or out-of-band spectrum) of the thermal source must be recycled to the source. Current approaches for photon recycling use back-surface reflectors or front surface filters, however, these have not exceeded 95 % out-of-band reflectance. In this work, we demonstrate an out-of-band reflectance of ~99% in a thin-film In0.53Ga0.47As TPV using an air-bridge as photon reflector, which effectively eliminates out-of-band absorption losses. The nearly perfect photon utilization enables a record high TPV power conversion efficiency of over 31% measured with a 1500K blackbody emitter.
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