| Popis: |
Thermophotovoltaic (TPV) cells, developed by LaPotin et al., were reported in Nature with efficiencies of 41.1% for a 1.4/1.2 eV 2-junction (2J) device irradiated by a tungsten emitter at 2400 C and 39.3% for a 1.2/1.0 eV 2J device irradiated by the tungsten emitter at 2127 C. These efficiency values were determined by including the reflection of the sub-bandgap photons; i.e., photons with energy less than the bandgap energy of the bottom subcell of the 2J TPV cells. Sub-bandgap photons are not absorbed by the TPV cells and therefore cannot be used to generate electric power. Thus, it is natural to question if there is any value in reflecting the sub-bandgap photons back for absorption in the emitter which will continue to radiate the same spectrum containing the same fraction of unusable sub-bandgap photons. As it turns out, the actual efficiencies of the TPV cells reported by LaPotin et al. are only 8.2% and 9%. Here, we show that it is more important to maximize the power output of TPV cells rather than maximizing the reflection of incident radiation. |
