Thermophotonics

Thermophotonics (TPX) is a recently proposed concept, which generalizes thermophotovoltaics (TPV) by allowing the radiation from the heat source to be increased by an internal electrochemical potential difference. This paper examines the basic working principle of TPX by means of detailed balance calculations. In these calculations TPX is not only modelled by the highly idealized standard Shockley-Queisser analysis but also in a more realistic manner, in which two typical parasitic loss mechanisms are included: (a) non-radiative recombination and (b) non-zero absorptivity/emissivity in the sub-bandgap energy spectrum. We show that TPX, in principle, allows a much higher rate of electrical power extraction from a heat source than TPV. When applying TPX to the conversion of solar energy we furthermore show that for a realistic absorber geometry TPX has a substantially higher theoretical conversion efficiency than TPV, particularly in the presence of parasitic sub-bandgap absorption/emission. Additionally, the range of suitable bandgap energies for TPX is greatly enhanced towards larger values over that of TPV. An essential requirement, however, is very high external electro-luminescent quantum efficiency.