“For the first time, we were able to a produce a nearly perfect metallic solar absorber, and we also demonstrated a 130% increase in thermoelectric generation efficiency” Chunlei Guo

New laser technology can improve upon solar power generation, according to a team from the University of Rochester in the US. Their study showed how strong femto-second laser pulses can etch metal surfaces with nanoscale structures that selectively absorb light only at the solar wavelengths and reducing heat dissipation at other wavelengths.

As reported in Materials Today, the lab of Chunlei Guo had recently used lasers to develop metallic structures that don’t sink regardless of how often they were forced into water or damaged. They had also developed laser processing technology that turns shiny metals almost pitch black and able to capture incoming radiation over an ultrabroad wavelength range, including the solar range. However, with the black metal some of the absorbed energy is dissipated through heat so, as reported in Light: Science & Applications [Jalil et al. Light Sci. Appl. (2020) DOI: 10.1038/s41377-020-0242-y], the team further developed their femto-second laser etching technology to enhance control over spectral absorption.

With precise control of spectral absorption of the metal surface, the metal could absorb most strongly in the solar spectrum and minimize the heat loss in longer wavelengths. Aluminum, copper, steel and tungsten were tested, with tungsten – already found in regular use as a thermal solar absorber – offering the highest solar absorption efficiency when treated with the new nanoscale structures. As Chunlei Guo told Materials Today, “For the first time, we were able to a produce a nearly perfect metallic solar absorber, and we also demonstrated a 130% increase in thermoelectric generation efficiency”.

The approach improves spectral absorption since the surface not only enhances the energy absorption from sunlight, but also reduces heat dissipation at other wavelengths, producing the first perfect metallic solar absorber. In addition, solar energy harnessing was demonstrated using a thermal electric generator device, and a similar process worked to change the color of a range of metals, such as blue, golden and gray, in addition to the black.

Applications for the technology could involve color filters and optical spectral devices, and even manufacturing automobiles of different colors with a single laser. As the efficiency of thermoelectric generation is relatively low, the technology holds great potential not only for harnessing solar energy but also in waste heat management, and the team are looking to further refine heat management for even greater thermoelectric generation efficiency, as well as investigating a range of other energy-related research that takes advantage of the technology.