Femtosecond Laser Light Etching Could Turn Future Windows Into Transparent Solar Panels

Researchers from the Ecole Polytechnique Fédérale de Lausanne (EPFL) and the Tokyo Institute of Technology have come up an approach that could one day turn windows into fully-transparent energy-harvesting generators for the buildings in which they're fitted: by blasting tellurite glass with laser light.

"Tellurium being semiconducting […] we wondered if it would be possible to write durable patterns on the tellurite glass surface that could reliably induce electricity when exposed to light, and the answer is yes," explains Yves Bellouard of the team's work, which builds on the discovery that laser-blasted tellurite forms nanoscale semiconducting tellurium and tellurium oxide crystals.

“An interesting twist to the technique is that no additional materials are needed in the process," Bellouard adds. "All you need is tellurite glass and a femtosecond laser to make an active photoconductive material."

Using small pieces of tellurite glass made at Tokyo Tech, the EPFL team exposed it to a femtosecond laser — etching a simple pattern of lines into the surface. These lines, owing to their exposure to the laser, act as semiconductors — and, more importantly, turned both visible and ultraviolet light into an electrical current that could be captured at test points on the PCB in which the glass was mounted.

"It’s fantastic, we’re locally turning glass into a semiconductor using light," Bellouard, who leads the EPFL's Galatea Laboratory, says of the team's discovery. "We're essentially transforming materials into something else, perhaps approaching the dream of the alchemist!"

While the process has the potential to turn every window into a solar panel, though, there are a few hurdles to jump before commercialization. While the test device proved stable over a period of months, it also measured just 1cm (around 0.4") in diameter — with no demonstration yet of a large-scale implementation.

The team's work has been published in the Physical Review Applied journal, under open-access terms.

Main article image courtesy of Lisa Ackermann/EPFL.