Efficient solar energy harvesting via thermally stable tungsten-based nanostructured solar thermophotovoltaic systems

Abstract

Electromagnetic radiations are a key energy source, which, by deploying bandgap-engineered devices, are directed onto PV cells to maximize their utilization. In this regard, the Solar Thermophotovoltaic (STPV) systems are vital, consisting of an intermediate absorber-emitter assembly between sunlight and solar cells. A theoretical and computational demonstration of a highly thermally robust, angularly stable, polarization-insensitive, and compact tungsten-based broadband absorber and spectrally selective emitter in symmetric metal-insulator-metal (W-SiO2-W) configuration has been presented. The nanoscale absorber consists of four differently-sized cylinders forming a supercell, and the emitter is cylindrical. The absorber has been optimized over a range of operating temperatures and solar irradiances, manifesting a very high absorption for the visible region with an average of 98.09 % for 400 – 800 nm, exhibiting > 99 % absorption for a BW of 225 nm with a peak of 99.99 % at 674 nm. The emitter has been optimized with 99.72 % emissivity at the desired spectral location. The absorber’s intermediate efficiency is 99.91 % for 5000 suns at 800 °C, which is as high as 72.33 % at a target temperature of 3200 °C. This study aims to match a higher bandgap of 1.5 eV perovskite solar cells and realize higher efficiency than tandem solar cells. The solar cell efficiency is 42.39 %, which results in solar-to-electricity efficiency of 42.38 %, exceeding the Shockley-Queisser (SQ) limit. As a proof-of-concept using a simulation program SCAPS-1D, a perovskite solar cell is illuminated using a bandgap-matched photon, increasing its efficiency from 26.67 % to 45.79 %. Thus, the presented idea achieves cell efficiency beyond the SQ limit without employing complex tandem cells.