Stacked Plasmonic TiN Nanodisks for High-Temperature Broadband Solar Energy Absorption and Efficient Photothermal Conversion

This paper presents a broadband, high.emissivity solar absorber designed for high.temperature operation. The structure consists of a periodic array of TiN nanodisks embedded in a dielectric stack on a TiN reflector, utilizing materials stable at elevated temperatures. The absorber exhibits an average absorptance of 94.9% and a total solar absorption efficiency of 95.1% across 400–2500 nm, closely matching the AM 1.5 spectrum. Its performance originates from the synergy of localized and propagating surface plasmon resonances, magnetic resonance, and impedance matching, as confirmed by electromagnetic field analysis. The design is polarization.insensitive and maintains high absorption (>80%) for incident angles up to 80° for both TM and TE polarizations. In addition, the absorber shows excellent thermal emission characteristics, retaining high radiation efficiency (e.g., 95.3% at 1500 K) over a broad temperature range, with a spectral shift obeying Wien’s law. The photothermal conversion efficiency remains notably high up to 1000 K (95.1% at 1000 K). These combined features make the proposed absorber a promising candidate for applications in solar thermal collection, thermophotovoltaics, selective emitters, and related high.temperature solar technologies.