THE use of plasmonic black metals could someday provide a pathway to more efficient photovoltaics (PV) –the use of solar panels containing photovoltaic solar cells – to improve solar energy harvesting, according to researchers at Lawrence Livermore National Laboratory (LLNL).

The LLNL Materials Engineering Division (MED) research team has made breakthroughs experimenting with black metals. These nanostructured metals are designed to have low reflectivity and high absorption of visible and infrared light. The MED research team recently published its black metals research results in Applied Physics Letters titled “Plasmonic Black Metals in Resonant Nanocavities.”

Authored by MED physicist and research team member Mihail Bora, the article details the work of the nanophotonics and plasmonics research team led by LLNL engineer Tiziana Bond.

It describes the team’s concept of black metals, which are not classic metals but can be thought of as an extension of the black silicon concept. When silicon is treated in a certain way, such as being roughened at the nanoscale level, it traps light by multiple reflections, increasing its solar absorption. This gives the silicon a black surface that’s able to better trap the full sun’s wavelength spectrum.

Similarly, black metals are produced by some sort of random nanostructuring – either in gold or silver – without guaranteeing a full, reliable and repeatable full solar absorption. However, Bond’s team developed a method to improve and control the absorption efficiency and basically turn the metals as black as they want, allowing them to increase, on demand, the absorption of a higher quantity of solar wavelengths.

This new LLNL technology could one day be used in the energy harvesting industry such as PV.