Engineers Develop Flexible, Inorganic LED Display

The promise of OLED technology is that, unlike its inorganic counterpart, it can be used to create flexible and nearly transparent ultra-thin screens, opening up myriad possibilities for what we can do with displays and lighting. But just as market-ready OLED technology suffered a setback as Sony delayed its latest OLED television this week (only the world’s second commercial OLED TV, after Sony's XEL-1 set), engineers have devised a way to make cheaper, more efficient inorganic LED technology bend to their whims. Literally.

Just what scientific innovation brought us this flexible LED technology? Make the LEDs smaller. But that’s easier said than done. LEDs are very efficient at converting electric charge to light, so the eye can detect even extremely small LEDs; therefore, in theory, even a display in which only a small fraction of the surface is actually covered by the LEDs is still visible to the naked eye when it’s lit. A layer of microscopic LEDs embedded in a material should bend and flex as that material does, but their small size allows transparent materials to retain their transparency when the LEDs aren’t glowing.

However, the manufacturing processes that churn out the LEDs in our televisions and other displays can’t manufacture LEDs the size of individual pixels. So the engineers came up with a novel approach: manufacture one big LED, and then pare it down into the tiny elements needed to build a transparent, flexible display. The researchers created one large red LED atop a substrate then devised a way to etch a square grid into the LED, leaving behind squares just 50 micrometers across. The individual squares were then anchored together at two corners and the substrate holding them together was removed, leaving just the tiny square LEDs.

This tightly-packed LED grid, however, would lack transparency, so the engineers then crafted a simple process for removing certain subsets of the LEDs–every fourth square, let’s say–and printing that subset onto whatever surface they chose. Add some very small, flexible wiring to create a complete circuit, and viola, you’ve got a flexible, transparent LED display.

While the technology is by no means market-ready right away, the fact that the procedure works with established processes and materials means engineers should be able to develop the technology fairly quickly. Will it leapfrog more expensive, less energy efficient OLED tech? Probably not, but once manufacturing is scaled to mass produce flexible LEDs, it will immediately bring the price of flexible displays down, potentially bringing them to more applications faster than OLED could alone.