High Temperature Spectrally Selective Solar Absorbers Using Plasmonic AuAl₂:AlN Nanoparticle Composites

Abstract

Advanced solar energy collectors require the use of thermally stable and spectrally selective coatings in order to boost absorption of radiant energy. Here, it is shown that incorporation of plasmonically resonant Au and AuAl2 nanoparticles into multilayer coatings based on AlN provides strong and stable absorption across the solar spectrum at temperatures between RT and 500 °C. Optical properties at operating temperature are verified using in situ measurements. Solar absorptance of 92–97% is available in the as‐deposited films, which are comprised of layers of Al, Au:AlN, AlN, and SiO2. Annealing at the operating temperature of ∼500 °C causes the conversion of the elemental Au to the intermetallic compound AuAl2, but the good solar absorbing performance is retained. The additional Al that reacts with the Au nanoparticles to form the AuAl2 diffuses up from the reflective Al substrate used. Enhanced NIR solar absorptance post‐annealing is accompanied by a tolerable small rise in thermal emittance. Formation of AuAl2:AlN also prevents undesired Au nanoparticle agglomeration above 500 °C. This suggests that AuAl2:AlN nanoparticle composites are excellent candidates for solar thermal applications up to about 500 °C.

The Quest for Zero Loss: Unconventional Materials for Plasmonics

“…However, other considerations can apply. For example, AuAl 2 nanoparticles seem less susceptible to thermally induced coarsening than those of Au, suggesting possible applications in spectrally selective films intended for application in the 300–500 °C range …”

An Ultrathin, Nanogradient, and Substrate‐Independent WOx‐Based Film as a High Performance Flexible Solar Absorber

“…Currently, solar selective absorber coatings (SSACs), which are mainly used to harvest sunlight and convert it into a heat source, are being increasingly used in solar‐thermal applications, such as concentrated solar power (CSP) systems, solar thermal collectors (STCs), solar thermophotovoltaic (STPV) systems, solar‐heated clothes and cookers, flexible electronic devices, and solar steam generators (SSGs) . To boost the light‐to‐heat conversion efficiency, a range of novel SSACs have been designed and demonstrated to date, where double‐cermet‐based SSACs are believed to be the most efficient materials for enhanced light absorption due to the interference effect of cermet layers and plasmonic resonance effect of metal nanoparticles, for instance, Mo‐SiO 2 , W‐Al 2 O 3 , Mo‐Al 2 O 3 , W‐AlN, AuAl 2 ‐AlN, AgAl‐Al 2 O 3 , WNi‐YSZ, and so forth . In general, such traditional cermet absorbers have a thickness in the range of 150–400 nm and are fabricated with a complicated co‐sputtering process, which is not a low‐cost, flexible process for large‐scale production.…”

Transparent Refractory Aerogels for Efficient Spectral Control in High‐Temperature Solar Power Generation

“…[ 41–43 ] For context, Figure 5b shows the temperature, time, and environment (air vs vacuum) used to age the various materials. [ 16,43–50 ] Importantly, the refractory aerogel in this work has been aged in air and for a significantly longer duration than its counterparts. The receiver efficiency of the refractory aerogel is 75% after aging at 700 °C for 10 days.…”