Fig. 1.

Increasing the efficiency of thermophotovoltaics by managing the low-energy thermal photons that cannot be absorbed by the semiconductor. There are two approaches for doing this. (A) Use a spectrally selective coating that will ideally emit high-energy photons or (B) exploit the semiconductor band edge itself as the spectral filter. The presence of a rear mirror ensures that any unabsorbed photons are reflected back to the emitter and are rethermalized.