Description
A thermoradiative diode (TRD) is a low-bandgap optoelectronic device that generates power through thermal emission to a colder environment. Its operation can be explained with a simple detailed balance model, where in an ideal device, current is given by the difference between emitted and absorbed photons. When more photons are emitted than absorbed from the cold environment, the device generates a photocurrent; when no current is extracted, a reverse bias develops across the diode [1]. This is the inverse of photovoltaic operation, where current flows due to higher absorption and a forward bias develops at open circuit.
In terrestrial power generation applications, a TRD can use the warm Earth as a hot reservoir and emit infrared radiation to the cold night sky. In the limit where the diode emits from a 300K Earth directly into 3K outer space, a power density of 54.8 W.m$^{-2}$ could be generated by an ideal, very low bandgap device. In more realistic terrestrial applications, the diode’s bandgap should be chosen to target the higher-transparency atmospheric window from 0.09-0.16 eV. Previous work captured the variable transmissivity of this window using effective sky temperatures, but accurate assessment of the potential power output must consider the spectral shape of the atmospheric downwelling radiation. Here, accurate radiative transfer modelling of the downwelling radiation is used to evaluate a TRD’s performance under nine representative atmospheric conditions. Under these conditions, an ideal device yields power densities between 0.34 and 6.5 W.m$^{−2}$, with optimal bandgaps near 0.094 eV. Accounting for stronger non-radiative processes at lower bandgaps, we also map the trade-off between a bandgap in the main atmospheric window and a higher bandgap in a secondary window with a better radiative efficiency [2].
[1] Nielsen et al., Nature Photonics, Nov. 2024, doi: 10.1038/s41566-024-01537-5.
[2] Harrison et al., iScience, Dec. 2024, doi: 10.1016/j.isci.2024.111346.
| I am the presenting author | Yes |
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