Semiconductor-based selective emitter with a sharp cutoff for thermophotovoltaic energy conversion.

A semiconductor emitter can possibly achieve a sharp cutoff wavelength due to its intrinsic bandgap absorption and almost zero sub-bandgap emission without doping. A germanium-wafer-based selective emitter with front-side antireflection and backside metal coating is studied here for thermophotovoltaic (TPV) energy conversion. Optical simulation predicts the spectral emittance above 0.9 in the wavelengths from 1 to 1.85 µm and below 0.2 in the sub-bandgap range with a sharp cutoff around the bandgap, indicating superior spectral selectivity behavior. This is confirmed by excellent agreement with indirectly measured spectral emittance of the fabricated Ge-based selective emitter sample. Furthermore, the TPV efficiency by pairing the Ge-based selective emitter with a GaSb cell is theoretically analyzed at different temperatures. This Letter facilitates the development of the semiconductor-based selective emitters for enhancing TPV performance.