Next-gen LEDs may substitute platinum, iridium with birch leaves

A birch-curtain in November in Ystad, Sweden. (Image by Jonn Leffmann, Wikimedia Commons.)

An international team of researchers led by physicists at Sweden’s Umeå University discovered that by pressure-cooking birch leaves, it is possible to produce a nanosized carbon particle with properties suitable for semiconductors for optoelectronics.

Their goal is to replace petrochemical compounds and metals such as platinum and iridium in organic LEDs for super-thin TV and mobile phone screens with a more sustainable alternative.

In a paper published in the journal Green Chemistry, the scientists explain that the synthesis process is simple: They picked birch leaves on the Umeå campus and cooked them in a pressure cooker.

This produced ‘carbon dots’ about two nanometers in size that emit a narrow-band, deep red light when dissolved in ethanol. Some of the optical properties of these birch leaf carbon dots are comparable to commercial quantum dots currently used in semiconductor materials, but unlike them, they contain no heavy metals or critical raw materials.

“It is important to note that our method is not limited to birch leaves,” Jia Wang, co-author of the study, said in a media statement. “We tested different plant leaves with the same pressure cooking method, and all of them produced similar red-emitting carbon dots. This versatility suggests that the transformation process can be used in different locations.”

Using the carbon dots in a light-emitting electrochemical cell device, the researchers were able to show that the brightness generated was 100 cd/m2, which is comparable to the light intensity from a computer screen.

“This result shows that it is possible to transition from depleting petroleum compounds to regenerating biomass as a raw material for organic semiconductors,” Wang said.

For the researcher, the carbon dots have broader potential beyond just light-emitting devices.

“Carbon dots are promising across various applications, from bioimaging and sensing to anti-counterfeiting. We’re open to collaborations and eager to explore more exciting uses for these emissive and sustainable carbon dots,” the scientist said.