Fireflies inspire OLED efficiency gains

April 21, 2016 // By PAUL BUCKLEY
The biologically inspired OLED is patterned with hierarchical structures very similar to those on a firefly. Credit: Kim, et al. ©2016 American Chemical Society
Researchers at the Korea Advanced Institute of Science and Technology have replicated the patterns of a firefly's light-emitting cuticle to create a bioinspired OLED that achieves a 60% increase in the light extraction efficiency and 15% wider angle of illumination.

The research findings have been published in a paper on the firefly-inspired OLEDs in Nano Letters.

Many insects, birds, fish, and amphibians emit light as a way to communicate with each other, but the species that produces light most efficiently is the firefly.

"This work reports the first observation of hierarchical structures, i.e., inclined microstructures with nanostructures existing on the cuticular ultrastructures of a firefly's lantern," said Jeong. "Based on our large-scale photonic calculation, it was clearly revealed that the function of asymmetric and hierarchical structures substantially contributes to the efficient extraction and wide angular illumination of bioluminescent light that would otherwise be entrapped in the firefly lantern. The knowledge learned from firefly lanterns has been successfully utilized for next-generation OLEDs."

The work builds on previous research (some by the same authors) that has shown that firefly cuticles have nanostructures that improve light transmission. The cuticles also have tiny structures that increase light extraction (the amount of light that actually exits the animal) by reducing internal reflection. The problem of internal reflection is one of the biggest challenges facing LEDs, where often more than half of the light produced is reflected back into the device rather than being emitted. Scientists have already mimicked these nano- and microstructures in LED design to improve light transmission and extraction.