KAIST team develops flexible blue vertical micro LEDs
Keon Jae Lee from KAIST (Korea Advanced Institute of Science and Technology) and his team have developed a low cost production technology for thin-film blue flexible vertical micro LEDs (f-VLEDs) made from GaN.
Micro LED is a sub-100 um light source for red, green and blue light, which has advantages of outstanding optical output, ultra-low power consumption, fast response speed, and excellent flexibility. To widely commercialise micro LEDs for mobile and TV displays, the transfer method of thin film micro LEDs requires a one-time transfer of one million LEDs. In addition, highly efficient thin-film blue micro LED is crucial for a full-colour display.
The team developed thin-film red f-VLED in previous projects, and now has realised thousands of thin-film blue vertical micro LEDs (thickness < 2 μm) on plastics using a one-time transfer. They reported their results in the latest issue of Advanced Materials.
The blue GaN f-VLEDs achieved optical power density (~30 mW/mm2) three times higher than that of lateral micro LEDs, and a device lifetime of 100,000 hours by reducing heat generation. These blue f-VLEDs could be conformally attached to the curved skin and brains for wearable devices, and stably operated by wirelessly transferred electrical energy, according to the researchers.
Lee said: "For future micro LEDs, the innovative technology of thin-film transfer, efficient devices, and interconnection is necessary. We plan to demonstrate a full-colour micro LED display in smart watch sizes by the end of this year. "
'Monolithic Flexible Vertical GaN Light Emitting Diodes for a Transparent Wireless Brain Optical Stimulator' by Han Eol Lee et al; Advanced Materials, June 2018 .
