Window into tellurite glass solar panels

In a discovery that is approaching an "alchemist's dream", a team of scientists from the Swiss Federal Institute of Technology Lausanne and Tokyo Tech has transformed glass into a light-powered semiconductor that could be the window into future clean energy generation.

Interested in the behavior of atoms in tellurite glass when exposed to ultrafast bursts of high-energy laser light, the researchers were surprised that a short burst of energy over one femtosecond, or one quadrillionth of a second (that's 15 zeroes), created tiny crystals of tellurium and tellurium oxide, both semiconducting materials, inside the glass, precisely where it was concentrated.

Immediately this led the team to conclude that this glass could generate electricity if exposed to sunlight.

"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," said Yves Bellouard who runs Swiss Federal Institute of Technology Lausanne's (EPFL) Galatea Laboratory.

The team was thrilled with this discovery and saw the potential for creating durable patterns on the glass surface that could produce electricity when illuminated. This is a significant breakthrough because the technique does not require any additional materials, and only two things are needed to create an active photoconductive material.

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

Sounds simple enough, with glass being simply superheated sand – except tellurium is one of the least common elements on Earth. Averaging roughly three parts per billion in Earth's crust, tellurium is rarer than the so-called rare earths, and about eight times less abundant than gold.

While uncommon, appreciable amounts of tellurium are produced each year to cover experimentation, notwithstanding the possibility of recycling future tellurite glass.

As for FS lasers, developed in the 1990s, typical uses exist in several eye-related medical procedures, with a very well-known use in LASIK laser eye surgery.

By etching possible photoconductive pathways on glass, the technology begins to open up to the possibilities of what this could present for applications that continue to get smaller and smaller.

Using tellurite glass provided by the collaborators at Tokyo Tech, the team applied their expertise in FS laser technology to modify the glass and study the effect of the etchings.

From this, they discovered that by drawing a simple line pattern on the surface of the tellurite glass disc roughly one centimeter in diameter, they could create a device capable of generating a current when exposed to UV light and even the visible spectrum, which the researchers say could last for months without degradation.

The team reiterated the potential of this discovery could revolutionize how glass can be used in daily living. With the growing need for renewable technologies – considering the massive amount of space that a window takes up – if each could become an active solar panel, the buildings themselves could become generators of clean energy.

"It's fantastic, we're locally turning glass into a semiconductor using light," said Bellouard. "We're essentially transforming materials into something else, perhaps approaching the alchemist's dream."