Swedish researchers have developed a transparent material made out of wood which they say could be used as windows, facade elements and even in solar panels.

The “optically transparent wood” developed by Stockholm’s Royal Institute of Technology is suitable for mass production, according to its creators, who’ve detailed the discovery in the American Chemical Society journal Biomacromolecules.

Professor Lars Berglund from KTH’s Wallenberg Wood Science Center, said that while optically transparent wood had been developed on a microscopic level before, this is the first time a method had been developed that allowed for the material to be produced on a large scale.

The wood is first chemically treated to remove lignin.

“When the lignin is removed, the wood becomes beautifully white,” Professor Berglund said. “But because wood isn’t not naturally transparent, we achieve that effect with some nanoscale tailoring.”

This is done by impregnating the white porous veneer substrate with a transparent polymer. The optical properties of the two are then matched, he said.

According to Professor Berglund, the discovery means that windows and solar panels could in the future be made from wood, which he described as one of the best and cheapest construction materials.

“Transparent wood is a good material for solar cells, since it’s a low-cost, readily available and renewable resource,” he said. “This becomes particularly important in covering large surfaces with solar cells.”

In the experiment, the wood sample had a transmittance up to 85 per cent, and also a haze of 71 per cent, which the researchers said would be attractive for solar cell applications, as light would be “trapped in the solar cell for longer”.

The wood could also be used for semitransparent facades, where both light and privacy are needed.

“No one has previously considered the possibility of creating larger transparent structures for use as solar cells and in buildings,” Professor Berglund said.

The next step is enhancing transparency and, as is the case with new materials, working to scale up the manufacturing process and create an economic proposition.

“We also intend to work further with different types of wood,” he said.

“Wood is by far the most used bio-based material in buildings. It’s attractive that the material comes from renewable sources. It also offers excellent mechanical properties, including strength, toughness, low density and low thermal conductivity.”

While the study found the material was structurally sound and functional, no mention is made of flammability, which could restrict its use in buildings.

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