A University of Rochester research team has demonstrated that the laser-based technology it used to create unsinkable metallic structures can also be used to create highly efficient solar power generators. The researchers used femtosecond (fs) laser pulses to etch metal surfaces with nanoscale structures that selectively absorb light only at the solar wavelengths. The etched surface not only enhances the energy absorption from sunlight, but also reduces heat dissipation at other wavelengths, in effect, “making a perfect metallic solar absorber for the first time,” professor Chunlei Guo said. Using femtosecond lasers to etch metallic structures, University of Rochester Institute of Optics professor Chunlei Guo and his team have developed a technique that can be used to collect sunlight to heat etched metal surfaces, which can then power an electrical generator for solar power. Courtesy of J. Adam Fenster/University of Rochester. The researchers experimented with different metal surfaces, specifically aluminum, copper, steel, and tungsten, and found that tungsten had the highest solar absorption efficiency when treated with the nanoscale structures. The tungsten selective solar absorber exhibited excellent performance as a high-temperature solar receiver. When integrated into a solar thermoelectric generation device, the tungsten selective solar absorber provided about a 130% increase in solar thermoelectric generation efficiency, compared to untreated tungsten, which is commonly used as an intrinsic selective light absorber. To allow fs-laser-treated tungsten to operate as a high-temperature selective solar absorber in ambient environments, the researchers sealed the tungsten surface with a dielectric thin film. They used titanium dioxide (TiO2) for the film because it had limited absorption within the team’s blackbody radiation wavelength range of interest. Tungsten absorbers coated with TiO2 were shown to withstand annealing at 500 °C without any noticeable degradation in their absorption properties. The lab has also used the fs laser etching technology to create superhydrophobic (water repellent) and superhydrophilic (water-attracting) metals. In November 2019, Guo’s lab reported creating metallic structures that do not sink no matter how often they are forced into water or how much damage they incur. The researchers said that they are the first to produce fs-laser-treated surfaces that can act as high-temperature absorbers for enhanced thermoelectric generation efficiency. The technology could be useful for any thermal solar energy absorber or harvesting device, particularly in places with abundant sunlight. The research was published in Light: Science & Applications (www.doi.org/10.1038/s41377-020-0242-y). The University of Rochester research lab that recently used lasers to create unsinkable metallic structures has now demonstrated how the same technology can be used to create highly efficient solar power generators. In a paper in Light: Science & Applications, the lab of Chunlei Guo, a professor of optics, describes using powerful femtosecond laser pulses to etch metal surfaces with nanoscale structures that selectively absorb light only at the solar wavelengths but not elsewhere. Courtesy of Matthew Mann/University of Rochester.