The sharpness of images on MicroLED screens is limited by how close together the pixels that make up the display are. Scientists at MIT took a unique approach to packing pixels closer together by vertically stacking their components.
In a typical OLED TV (or computer screen) each pixel is actually made up of three OLED sub-pixels (red, green and blue) arranged side by side. By lighting these tiny OLEDs in different combinations, the pixels can produce a wide range of colors.
Some newer TVs have micro-LEDs acting as sub-pixels instead of OLEDs. Such MicroLED TVs are claimed to combine the vivid colors and deep blacks of OLED screens with the brightness of LCD screens.
However, micro-LED pixels cannot be packed as densely as OLED pixels. While this may not be much of an issue on TV screens, the resolution loss can be noticeable on devices such as VR headsets.
Each Micro LED Pixel one Using a sub-pixel width (instead of 3) allows you to pack three times as many pixels into a given screen space, greatly improving image resolution. The MIT team did just that by creating vertically stacked pixels instead of arranging micro-LEDs horizontally.
Led by an associate. Professor Jeehwan Kim’s research team has developed a technique for stacking ultra-thin red, green, and blue LED films to form cake-like arrangements. The “cake” is then sliced into small grids and divided into a large number of individual pixels. Each pixel is just 4 microns wide.
In laboratory tests, by varying the voltage applied to each micro-LED within a pixel, researchers were able to produce rainbow colors like those possible in OLED pixels. But wouldn’t the blue micro LEDs at the top of the stack always show the most and the red micro LEDs at the bottom always show the least?
“The color (energy) of the light emitted by an LED depends on the band gap of the LED. Blue LEDs have the widest band gap (and thus have the highest energy in blue light), while red LEDs have the smallest band gap ( It has the lowest energy),” explains writer Shin Ji Ho. “Because the material does not absorb light (photons) with energies less than the bandgap, red and green light is transmitted through the blue LED layers without being absorbed. Stack vertically.(middle), B(top)”.
Scientists are now working on how to simultaneously control the millions of micro-LED pixels needed in devices such as VR headsets, TVs and computer screens.
A paper on this study was recently published in the journal Nature.
Source: MIT
