Numerically investigating the optical properties of plasmonic metallic nanoparticles for effective solar absorption and heating

Solar heating with plasmonic nanoparticles (NPs) has great potential for application in optical storage, solar thermal collectors, and thermo-photovoltaic technologies. The performance of solar thermal conversion applications depends on the NP parameters. Herein, we present a comparative analysis of the solar absorption properties of noble metallic NPs (Au, Ag, Cu, and Al), to determine suitable parameters for effective solar heating by using the finite-difference time-domain method and the finite-element method. Results show that light absorption plays a major role in the interaction of light with the small NP size, small sphericity, or small dielectric constant of the surrounding environment. Au and Cu NPs have higher solar absorption power and absorption ratio. The NP size has little effect on the peak absorption wavelength. A Au sphere smaller than 30 nm has greater solar absorption ability for the solar heating process when considering the absorption power per unit volume. The solar absorption power first increases rapidly and subsequently decreases slightly with increasing dielectric constant, and can become as high as 0.0045 nW when the dielectric constant is 1.33-2.5 in the calculation samples. The solar scattering power and solar absorption power decrease with increasing sphericity, i.e., ranging from cubic to cylindrical and spherical. Finally, simulation results of NP solar heating show that the Au cube obtains a higher maximum temperature than the Au sphere and Au cylinder, which further verifies that Au NPs with low sphericity can significantly enhance solar heating ability in the simulation cases.