A Highly Efficient, Selective, and Thermally Stable Dielectric Multilayer Emitter for Solar Thermophotovoltaics

Herein, the design, optimization, fabrication, and characterization of a highly efficient selective emitter (SE) for solar thermophotovoltaic systems is presented. An SE consisting of three layers (SiNx–SiO2–TiO2) deposited on a tungsten substrate is optimized for use with photovoltaic (PV) cells based on III–V semiconductors, such as GaSb, InGaAs, and InGaAsSb. The fabricated SE shows an emitter efficiency (ηSE) of 50% when coupled with a PV cell having an energy bandgap of 0.63 eV. After thermal treatment carried out at 1000 °C for 8 h in a vacuum environment, ηSE of 46% is recorded, demonstrating the thermal stability of the proposed SE. Its behavior at high temperatures has also been studied using simulations based on the transfer matrix method and on refractive indices experimentally measured at different temperatures (up to 1000 °C). The results show ηSE of 44% in the energy bandgap range of 0.55–0.63 eV, proving that the proposed structure is promising and can operate at high temperatures. In addition, the behavior of a real PV cell is simulated, and calculations show a maximum PV cell efficiency of 15% at 1000 °C and 25% at 1600 °C, exceeding the Shockley–Queisser limit.