Li-Fi (Light Fidelity) is a wireless communication technology that uses the visible light spectrum (400–800THz) similar to that of LED lamps, achieving speeds up to 224Gbps—100 times faster than current Wi-Fi. While Li-Fi faces fewer restrictions on available frequency allocation and experiences less radio interference, it is relatively vulnerable to security breaches because anyone can access the light signals.

Korean researchers have now proposed a new Li-Fi platform that overcomes the limitations of conventional optical communication devices, simultaneously enhancing both transmission speed and security.

A research team led by Professor Himchan Cho from the Department of Materials Science and Engineering, in collaboration with Dr. Kyung-geun Lim from the Korea Research Institute of Standards and Science (KRISS), has developed a device-level encrypted optical communication technology using Li-Fi, which is gaining attention as a next-generation ultra-high-speed data communication technology.

Professor Cho's team utilized environmentally friendly quantum dots (low-toxicity and sustainable materials) to create high-efficiency light-emitting triode devices. The developed device employs a mechanism that generates light through an electric field. Specifically, the electric field is concentrated in tiny holes (pinholes) on a permeable electrode and transmitted beyond the electrode. This device processes two input data streams simultaneously using this principle.

Based on this mechanism, the team developed a technology called "device-embedded encrypted optical transmitter." The core of this technology is that the device itself converts information into light and encrypts it at the same time. This enables enhanced-security data transmission without the need for complex separate equipment. The research was published in Advanced Materials.

External quantum efficiency (EQE), a measure of how efficiently electrical energy is converted into light, typically reaches around 20% in commercial standards. The newly developed device achieved an EQE of 17.4% and a brightness of 29,000 nits—more than 10 times brighter than the maximum brightness of smartphone OLED screens (2,000 nits).

Additionally, to precisely understand how the device converts information into light, the team used a technique called transient electroluminescence analysis. They examined the light emission characteristics when voltage was applied instantaneously over extremely short durations.

Through this analysis, they studied the movement of charges inside the device within hundreds of nanoseconds, elucidating the operating mechanism that enables dual-channel optical modulation within a single device.

Professor Himchan Cho from KAIST stated, "This research overcomes the limitations of existing optical communication devices and proposes a new communication platform that simultaneously improves transmission speed and enhances security."

"This technology enhances security without additional equipment while performing encryption and transmission at the same time, making it applicable across various fields where security is critical in the future."