Titanium nitride selective absorber enhanced solar thermoelectric generator (SA-STEG)

Solar thermoelectric generator (STEG) system has been intensively studied due to its reliability and environment-friendly property. In a STEG system, a solar absorber is an important component because it not only absorbs the solar energy, but also emits photons to environment as radiation heat loss. In this study, a selective absorber enhanced STEG system (SA-STEG) is presented. A Titanium nitride (TiN) based 2D photonic crystal (PhC) selective absorber is fabricated, which possesses a high absorptivity at short wavelength range to fully absorb the solar energy, but a suppressed absorptivity at long wavelength range to avoid the radiation loss. The selective absorber also keeps a good wavelength selectivity even after a thermal annealing over 1000 K. The selective absorptivity data were imported into the SA-STEG model and an improvement was obtained: for a Lead telluride STEG system, a 28 K temperature increase was achieved, and for a Silicon germanium alloy STEG system a 32 K temperature increase was achieved. The increased temperature yields a larger open-circuit voltage output. These results were attained based on a 40 × 40 mm2 STEG system and this value is expected to be further increased if a larger thermoelectric generator is employed.