Transforming glass into a “transparent” light energy harvester

What happens when you expose tellurite glass to femtosecond laser light? This is the question that Gözden Torun from the Galatea Lab at the École Polytechnique Fédérale de Lausanne, in collaboration with scientists from Tokyo Tech, wanted to answer in her thesis work when she made the discovery that could one day transform windows made of a single material capturing and capturing light. devices. The results are published in Applied physical examination.

Interested in how the atoms in tellurite glass would rearrange themselves when exposed to rapid pulses of high-energy femtosecond laser light, scientists stumbled upon the formation of tellurium crystals and tellurium oxide at the nanoscale, two semiconductor materials etched into the glass, precisely where the glass had been etched. been exposed. For scientists, it was the eureka, because a semiconductor material exposed to daylight can lead to the production of electricity.

“Since tellurium is a semiconductor, we wondered whether it would be possible to write long-lasting patterns on the surface of tellurite glass that could reliably produce electricity when exposed to light, and the answer is yes”, explains Yves Bellouard, director of the Galatea Laboratory at EPFL. . “An interesting feature of the technique is that no additional materials are needed in the process. All you need is tellurite glass and a femtosecond laser to make an active photoconductive material.”

Using tellurite glass produced by colleagues at Tokyo Tech, the EPFL team brought its expertise in femtosecond laser technology to modify the glass and analyze the effect of the laser. After exposing a simple pattern of lines on the surface of a 1 cm diameter tellurite glass, Torun discovered that it could generate a current when exposed to UV light and the visible spectrum, reliably for months.

“It’s fantastic, we locally transform glass into a semiconductor using light,” declares Yves Bellouard. “We are essentially transforming materials into something else, which perhaps brings us closer to the alchemist’s dream.”