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Gözden Torun at the Galatea Lab of École Polytechnique Fédérale de Lausanne (EPFL), in collaboration with Tokyo Tech scientists, has introduced an innovative method for creating photoconductive circuits. This breakthrough involves directly patterning circuits onto a glass surface using femtosecond laser light, potentially paving the way for energy-harvesting applications that are transparent to light and utilize a single material.

The researchers focused on the effects of exposing tellurite glass to femtosecond laser light. During her thesis work, Torun discovered that this process leads to the formation of nanoscale tellurium and tellurium oxide crystals—semiconducting materials—precisely at the points of laser exposure. These findings indicate that semiconducting materials etched into the glass may generate electricity when exposed to daylight, opening new avenues for the development of light harvesting and sensing devices.

“Tellurium being semiconducting, based on this finding 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 who runs EPFL’s Galatea Laboratory. “An interesting twist to 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 their expertise in femtosecond laser technology to modify the glass and analyze the effect of the laser. After exposing a simple line pattern on the surface of a tellurite glass 1 cm in diameter, Torun found that it could generate a current when exposing it to UV light and the visible spectrum, and this, reliably for months.

“It’s fantastic, we’re locally turning glass into a semiconductor using light,” says Yves Bellouard. “We’re essentially transforming materials into something else, perhaps approaching the dream of the alchemist!”.

Click here to read the paper titled, "Femtosecond-laser direct-write photoconductive patterns on tellurite glass."