Design of a metamaterial-based broadband absorber and selective emitter for solar thermophotovoltaic applications

This paper investigates a solar thermophotovoltaic (STPV) system composed of a broadband absorber, a selective emitter, and a low-bandgap photovoltaic (PV) cell. The finite element method (FEM) is used to simulate the spectral absorption and emission properties of both the absorber and the emitter. The proposed metamaterial (MTM) absorber, based on tantalum (Ta), nickel (Ni), and silicon dioxide (SiO₂), exhibits an absorption rate exceeding 90 % in the 250 nm – 1500 nm range, covering the UV, visible, and near-infrared (NIR) regions, and surpasses 99 % in the visible spectrum. Additionally, it achieves an absorption efficiency of 97.31 % under the AM1.5 spectrum and a thermal emission efficiency of 93.81 % at 1600 K. An MTM selective emitter, composed of Ta and SiO₂, is designed to reshape the thermal spectrum for InGaAsSb, GaSb, and InAs PV cells. The output power reaches 0.67, 1.54, and 1.96 W/cm² for InGaAsSb, GaSb, and InAs cells, increasing to 2.14, 2.62, and 3.11 W/cm² for InAs/InGaAsSb, InGaAsSb/GaSb, and InAs/InGaAsSb/GaSb tandem cells at 1600 K. With the absorber-emitter configuration forming the STPV intermediate structure, the system achieves 18.80 %, 14.80 %, and 6.48 % efficiency for InGaAsSb, GaSb, and InAs cells at 1600 K and a concentration (C) of 5000. Moreover, efficiencies exceeding 20 % are attained from 1400 K with C = 4500 for InAs/InGaAsSb cells, from 1600 K with C = 1920 for InGaAsSb/GaSb cells, and from 1400 K with C = 1740 for InAs/InGaAsSb/GaSb cells. These findings highlight the efficiency and adaptability of the proposed system, providing a basis for further STPV performance enhancements.