Made of nanorods arranged in a thin film, LEDs arrays that can both emit and detect light could enable new interactive functions and multitasking devices.
The 5nm nanorods are made of three types of semiconductor material. One type emits and absorbs visible light. The other two semiconductors control how charge flows through the first material.
According to the team, the LEDs switch so fast between emitting and detecting light that the display appears to stay on continuously – at rates three orders of magnitude faster than standard display refresh rates.
The researchers demonstrated pixels that automatically adjust brightness, as well as pixels that respond to an approaching finger, which could be integrated into interactive displays that recognise objects or respond to touchless gestures.
They also demonstrated arrays that respond to a laser stylus, which could be the basis of smart whiteboards, tablets or other surfaces for writing or drawing with light, and claim the LEDs can convert light to electricity.
“The way it responds to light is like a solar cell,” Professor Moonsub Shim from the University of Illinois said. “We still have a lot of development to do before a display can be completely self-powered, but we think that we can boost the power-harvesting properties without compromising LED performance.”
Nanorod LED displays can also interact with each other as large parallel communication arrays. Two LED arrays facing each other could potentially communicate with as many bits as there are pixels in the screen.