Infrared LEDs are usually used for optical communication and concealed lighting, and are often used in remote controls and security cameras. They are usually small point light sources, and their use will be limited if large areas of illumination are required at close range on wearable devices.
Recently, researchers at the National University of Singapore have developed high-efficiency, large-area and flexible near-infrared LEDs for new wearable device technologies.
The team led by Tan Zhi Kuang developed a high-efficiency near-infrared LED that uses a low-cost solution processing method to cover an area of 900 mm2.
Their equipment uses perovskite-based semiconductors. By using a new device architecture, the research team was able to precisely inject electrons and holes (negative and positive charges) into the perovskite, so that a certain amount of opposite charges could meet and produce effective light. The team also found that this improvement greatly improved the reproducibility of large-area equipment.
Xiaofei Zhao, a PhD student in the research team, said: "We found that hole injection efficiency is an important factor affecting device performance. By using organic semiconductors with lower ionization potential as part of the device structure, we can improve the hole Inject and achieve charge balance. This allows our devices to emit light with efficiencies close to their theoretical limits (external quantum efficiency of 20%), and also reduces performance differences between devices, resulting in larger devices. "
Tan Zhi Kuang said: "The technology supported by our device can include secret lighting in facial recognition or AR / VR eye tracking technology. In particular, we have proven that our LED can be applied to the application of deep tissue lighting, such as Wearable health tracking device. "
He added, "These materials can also be developed to emit light in a variety of visible colors. Therefore, they can be applied to a new generation of flat panel electronic displays." (Compiled by LED Network James)