I just read an article at optics.org about micro-pixellated LEDs, or MicroLEDs – these LEDs arrayed elements, with thousands or even tens of thousands of sources covering a surface. The University of Strathclyde's Institute of Photonics in the UK is at the edge of this technology right now, and leading. They've developed, according to the article, the highest performance microLED arrays ever.
From the article:
"We have developed a range of microLEDs in various formats, based on the light-emitting capabilities of gallium nitride (GaN) semiconductor materials," explained Simon Andrews, business development manager of the Institute of Photonics. "This allows us to generate what is in essence a programmable pattern of light."
Right now, the spectral output on these microLED arrays is pretty narrow, with UV, blue, and green arrays being the most created. Andrews also says in the article that red light is possible, but needs to start with a different material system. Again, from the article:
"We are working on ways to vary the wavelengths of light that can be emitted by the arrays," explained Andrews. "Our chemistry colleagues at Strathclyde, led by Richard Pethrick, have developed UV transmissive polymers, which increase the transmission of UV light well below 300 nm and down towards 200 nm, to match the wavelengths possible from the GaN alloys. We have blended in different light-emitting polymers to colour-convert UV light into red, green or blue light. In addition, we have blended in quantum dots that can colour-convert UV light into practically any colour that you wish, depending on the size of the dot. As quantum dot technology is becoming easier to source all of the time, this is a significant development."
Researches at the Institute are also working on different shapes as well – like this micro stripe.
Exciting! Go read the article, it's pretty lengthy, and I couldn't possibly have done it justice here.