Effects of nanoparticle structural features on the light-matter interactions in nanocermet layers and cermet-based solar absorbers

Metallic nanoparticle (NP)/ceramic composite cermets present desirable broadband absorption of the solar spectrum and thus are the preferred material scheme for constructing cermet-based solar absorbers. However, the effects of fine nanoparticle structural features on the light-matter interactions in nanocermet layers and corresponding cermet-based solar absorbers are still not well clear until now. Herein, we report a systematical investigation on the effects of W (tungsten) nanoparticle sizes, its concentrations and configurations in an alumina matrix on the optical responses of WAl2O3 nanocermet layers and a solar absorber with double-cermet layers. It is found that to possess admirable light absorption features at high temperatures, it is better to maintain the fine particle size of less than 10 nm, isolated states and suitable separations between them for WAl2O3 nanocermets. Thus, the dominated intrinsic absorption of W NPs, their plasmonic excitation and coupling effects among each other all contribute significantly to the broadband optical performance of the cermet layers and the whole absorber. More importantly, this study demonstrates a valuable criterion for maintaining optical performances of nanocermet layers and cermet-based solar absorbers under heating and thus their thermal robustness.