Flexible Blue Vertical Micro LEDs

Illustration of high-performance and high-density blue f-VLED arrays. (Source: Wiley-VCH / KAIST)

Korean researchers developed a crucial source tech­nology that will advance the commerciali­zation of micro LEDs. Keon Jae Lee from the Korea Advanced Institute of Science and Tech­nology KAIST and his team have developed a low cost production tech­nology for thin-film blue flexible vertical micro LEDs (f-VLEDs). Recently, micro LED TV was spotlighted as a strong candi­date for replacing the active-matrix organic light-emitting diode (AMOLED) display. 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.

However, the current display industry has utilized the indi­vidual chip transfer of millions of LED pixels, causing high produc­tion cost. Therefore, the initial market of micro LED TV will be estimated to a hundred thousand dollars for global premium market. To widely commercia­lize 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-color display.

The team developed thin-film red f-VLED in previous projects, and now has realized thousands of thin-film blue vertical micro LEDs (thickness < 2 μm) on plastics using a one-time transfer. 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.

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-color micro LED display in smart watch sizes by the end of this year.” (Source: KAIST)

Reference: H. E. Lee et al.: Monolithic Flexible Vertical GaN Light‐Emitting Diodes for a Transparent Wireless Brain Optical Stimulator, Adv. Mat., online 18 June 2018; DOI: 10.1002/adma.201800649

Link: Dept. of Materials Science and Engineering, Korea Advanced Institute of Science and Technology KAIST, Daejeon, Republic of Korea

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