Spectral Control for Thermophotovoltaic Energy Conversion

Thermo-photovoltaic spacecraft electricity generation

“…This ratio may improve in the near future because of improving photonic surface fabrication capability. Furthermore, the measurement of this below-bandgap reflectivity in (Fourspring et al, 2006) has been with an angle of incidence distribution of an omnidirectional source, while in our case the angle of incident is always nearly perpendicular which is optimal for the operation of the photonic interference filter. Therefore measurements results from (Fourspring et al, 2006) can be used as a conservative estimate.…”

“…Without a filter on the photovoltaic side, below-bandgap photon energy would be lost energy. It is advantageous to use a highly reflective tandem-filter (Fourspring et al, 2006) before the photovoltaic junction for reflecting back the longwavelength spectrum, which will be then absorbed at the thermal radiator. A tandem filter consists of two layers; a photonic surface for reflecting back 2 -6 micron wavelength photons, and a plasma filter for reflecting back 6 -10 micron wavelength photons.…”

“…Taking the current 95% reflection capability for conservative estimate, the loss ratio of below-bandgap photons at the filter -resulting from back-and-forth radiation between filter and core -is 0.05× (1−0.95× (1− )) −1 , where is the emissivity of the radiator core. Regarding above band-gap photons, 3% filter absorption has been found in (Fourspring et al, 2006).…”