Comparative Analysis of Graded-Index and Quarter-Wave One-Dimensional Photonic Crystal Filters for GaSb Thermophotovoltaic Cells

Abstract

Thermophotovoltaic (TPV) systems are important for the clean energy transition due to their applications in waste heat recovery, solar energy harvesting, and thermal energy grid storage. This study presents a comprehensive investigation of the performance of TPV systems equipped with one-dimensional photonic crystal filters. The optical characteristics of the filter comprised of porous SiO₂ nanoparticle and dense ZrO₂ films are numerically evaluated. The results demonstrate the choice of filter significantly influences the emitter temperature, power density, system efficiency, and spectral performance. Further, the analysis underscores the inherent tradeoff in designing optical filters between achieving elevated in-band transmittance and maximizing out-of-band reflectance. Under a constant flux of 60 W cm⁻² from a heat source a conventional double-stack quarter-wave optical filter achieves a TPV system efficiency of 28.9%. In contrast, an optimized filter structure, consisting of a double-stack modified quarter-wave optical filter, increases TPV system efficiency to 29.1%. Introducing the optimized filter with a graded index profile into the TPV system as a photon recycling tool results in a 27% TPV system efficiency. This is a significant improvement compared to the case without a filter, which has a system efficiency of 15.8%.