Professor Keon Jae Lee of the Department of Materials Science and Engineering and his team at Korea Advanced Institute of Science and Technology (KAIST) have developed a low-cost production technology for thin-film blue flexible vertical micro-LEDs (f-VLEDs) that could advance the commercialization of micro-LEDs, it is reckoned (Chang Wan Kim et al, ‘Monolithic Flexible Vertical GaN Light-Emitting Diodes for a Transparent Wireless Brain Optical Stimulator’, Advanced Materials, June 2018 issue).
At January’s Consumer Electronics Show (CES 2018) in Las Vegas, the micro-LED TV was spotlighted as a candidate for replacing the active-matrix organic light-emitting diode (AMOLED) display.
The micro-LED is a sub-100μm light source for red, green and blue light, which has the advantages of outstanding optical output, ultra-low power consumption, fast response speed, and excellent flexibility.
However, the display industry has been utilizing the individual chip transfer of millions of LED pixels, making production costs high. The initial market for micro-LED TVs is hence be forecasted to be just a hundred thousand dollars for the global premium market.
For the widespread commercialization of micro-LEDs for mobile and TV displays, the transfer method for thin-film micro-LEDs requires a one-time transfer of 1 million LEDs. In addition, the highly efficient thin-film blue micro-LED is crucial for a full-color display.
The team has developed thin-film red f-VLEDs in previous projects, and is has now realized thousands of thin-film blue vertical micro-LEDs (with a thickness <2μm) on plastics using one-time transfer.
The blue GaN f-VLEDs achieved optical power density of about 30mW/mm2 (three times higher than that of lateral micro-LEDs) and a device lifetime of 100,000 hours (about 12 years) by reducing heat generation. The blue f-VLEDs could be conformally attached to curved skin and brain for wearable devices, and stably operated by wirelessly transferred electrical energy.
“For future micro-LEDs, the innovative technology of thin-film transfer, efficient devices, and interconnection is necessary,” says Lee. “We plan to demonstrate a full-color micro-LED display in smart watch sizes by the end of this year.”
