The optical duality of tellurium powder for broadband solar energy harvesting

Pulverous materials for solar energy harvesting are urgently needed to alleviate the global energy crisis. We demonstrate that a broadband absorber made of Tellurium (Te) powder with a wide size distribution can absorb more than 85% solar radiation in the entire spectrum. Temperature of the absorber irradiated by sunlight can increase from 29° to 85°C within 100 s. By dispersing Te powder into water, the water evaporation rate is improved by three times under solar radiation of 78.9 mW/cm2. This photothermal conversion surpasses that of plasmonic or all-dielectric powder reported before. We also establish that the unique permittivity of Te is responsible for the high performance. The real part of permittivity experiences a transition from negative to positive in the ultraviolet-visible–near-infrared region, which endows Te powder with the plasmonic-like and all-dielectric duality. The total absorption covers the entire spectrum of solar radiation due to the enhancement by both plasmonic-like and Mie-type resonances. It is the first reported material that simultaneously has plasmonic-like and all-dielectric properties in the solar radiation region. These findings suggest that the Te powder can be expected to be an advanced photothermal conversion material for solar-enabled water evaporation.

A broadband perfect absorber made of Te powder with a wide size distribution synthesized by ns-LAL have been designed. Perfect absorption (more than 85%) can be achieved in the entire spectrum of solar radiation. The temperature of the fabricated absorber irradiated by sunlight rapidly increased from 29° to 85°C within 100 s. In addition, the water evaporation rate can be improved by three times that of pure water under the illumination of simulated sunlight of 78.9 mW/cm2 by dispersing Te powder into water (10 μg/ml). This good performance can be derived from the unique optical duality of Te powder. The real part of permittivity of Te transforms from negative to positive at the UV-vis–NIR region, which endows Te powder with optical duality. As the size increases from 10 to 300 nm, the Te powder gradually converts from a plasmonic-like material to a high-index all-dielectric material. These findings demonstrated that the Te powder is a promising powder material for solar energy harvesting, solar desalination, and photovoltaic device design.

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