Proposed Li-Fi platform is faster and more secure than Wi-Fi

Li-Fi (Light Fidelity) is a next-generation wireless communication technology that utilises the visible light spectrum (400–800 THz), offering speeds up to 100 times faster than existing Wi-Fi — but while it has fewer limitations in available frequency allocation and less radio interference, it is relatively vulnerable to security breaches as anyone can access it.

Now researchers at the Korea Advanced Institute of Science and Technology (KAIST), in collaboration with the Korea Research Institute of Standards and Science (KRISS) under the National Research Council of Science & Technology (NST), have developed on-device encryption technology for use in Li-Fi, resulting in a platform that overcomes the limitations of conventional optical communication devices and can simultaneously enhance both transmission speed and security. Their work has been published in the journal Advanced Materials.

Professor Himchan Cho’s team at KAIST created high-efficiency light-emitting triode devices using eco-friendly quantum dots, which are low-toxicity and sustainable materials. Each device provides a mechanism that generates light using an electric field. The electric field is concentrated in tiny holes (pinholes) in the permeable electrode and transmitted beyond the electrode. The device utilises this principle to simultaneously process two input data streams.

Using this principle, the research team developed what they call an on-device encryption optical transmitter. The core of this technology is that the device itself converts information into light and simultaneously encrypts it. This means that enhanced security data transmission is possible without the need for complex, separate equipment.

External quantum efficiency (EQE) is an indicator of how efficiently electricity is converted into light, with a general commercialisation standard of about 20%. The newly developed device recorded an EQE of 17.4% and its luminance was 29,000 nit, significantly exceeding the maximum brightness of a smartphone OLED screen (2000 nit), demonstrating a brightness more than 10 times higher.

Furthermore, to more accurately understand how their device converts information into light, the research team used a method called transient electroluminescence analysis. They analysed the light-emitting characteristics generated by the device when voltage was instantaneously applied for very short durations. Through this analysis, they investigated the movement of charges within the device at hundreds of nanoseconds, elucidating the operating mechanism of dual-channel optical modulation implemented within a single device.

“This research overcomes the limitations of existing optical communication devices and proposes a new communication platform that can both increase transmission speed and enhance security,” Cho said, with the new platform offering speeds up to 224 Gbps.

“This technology, which strengthens security without additional equipment and simultaneously enables encryption and transmission, can be widely applied in various fields where security is crucial in the future.”

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