LiFi breakthrough: OLEDs used to reduce interference

Researchers from South Korea’s Pohang University of Science and Technology (POSTECH), Ajou University and Inha University have found a way to implement visible light communication (VLC) in a practical lighting system — by reducing interference with a novel light source. Their findings have been published in the journal Advanced Materials.

LiFi, a communication technology harnessing visible light for data transmission, has the potential to surpass Wi-Fi’s speed by over 100 times and boasts a high bandwidth, facilitating the simultaneous transmission of copious information. Notably, LiFi ensures robust security by exclusively transmitting data to areas illuminated by light. Most importantly, it capitalises on existing indoor lighting infrastructure, such as LEDs, eliminating the need for separate installations.

Unfortunately, when light of the same wavelength intersects, interference occurs, resulting in the merging or cancellation of amplitudes and causing diminished stability and accuracy in data transmission. This phenomenon was observed by the researchers when using LEDs as a single-colour light source in VLC technology. To resolve this hurdle, the team developed a novel light source to replace the conventional one.

By combining red, green and blue organic light-emitting diodes (OLEDs), they crafted a light source that mimics standard white illumination but with minimal interference zones. Furthermore, the team introduced a cavity structure to enhance the OLEDs’ colour representation for each wavelength and incorporated a Fabry–Pérot structure into the light-absorbing organic photodiodes (OPDs) to selectively receive specific wavelengths of light.

The team’s composite white light exhibited a significantly lower bit error rate (BER) than that of conventional light sources; BER, representing the error ratio to the total transmitted bits, serves as a key quantifier of digital signal quality. This achievement signifies effective suppression of interference among light sources, ensuring accurate information transmission.

“In contrast to conventional light sources, our light source, which blends three wavelengths, circumvents interference, thereby enhancing stability and accuracy in data transmission,” said POSTECH’s Professor Dae Sung Chung, the leader of the consortium. “We foresee this technology as a potentially beneficial tool for diverse industries, serving as a next-generation wireless communication solution that utilises conventional lighting systems.”

Image caption: Organic VLC system based on mixed white light illumination and colour-selective OPDs fabricated with OLEDs.