(355e) Absorptive Spectral Control for High-Efficiency Thin-Film Thermophotovoltaics

Thermophotovoltaics (TPVs) are a promising technology for conversion of high-temperature heat to electricity. The technology’s solid-state design enables scalable implementation, making TPVs suitable for decentralized applications such as residential combined heat and power and small-scale solar thermal generators. To achieve competitive conversion efficiency in TPVs, it is important to suppress transport of sub-bandgap radiation between the emitter and PV cell. Here, we demonstrate a thin-film InGaAs cell with a highly reflective back-surface, exhibiting record high spectral selectivity (high sub-bandgap reflectance combined with high above-bandgap absorptance). We use selective absorption at the cell to facilitate sub-bandgap radiation recycle, resulting in significant improvements in TPV efficiency. To fabricate the InGaAs cells we integrated epitaxial InGaAs with various multilayer architectures composed of dielectric and metallic layers. We conducted a thorough experimental and computational study on these cells. Computational simulation was performed to characterize radiative transport and energy conversion in a parallel-plate TPV system. Optical, electrical, and materials characterization of several thin-film InGaAs cells served to refine our model’s predictions and diagnose sources of loss. The computational tool was then utilized to optimize the cell architecture for maximum efficiency. This study demonstrates a route toward high-performance, low-cost TPV devices and identifies a set of priorities for their design.