Flexible micro-LED array could open door to TV screens

The team transferred thousands of <2μm-thick blue vertical micro LEDs onto plastic in one go. Electrical connections are via silver wires.

Optical power density around 30mW/mm² was demonstrated. claimed by KAIST to be three times higher that would be achieved by lateral micro LEDs. Due to low heat dissipation, it is predicting 100,000h (12year) life, and 100,000 bending/unbending cycles has been demonstrated.

“These blue flexible vertical LEDs could be conformally attached to the curved skin and brains for wearable devices, and stably operated by wirelessly transferred electrical energy,” said the lab – the brain reference is to apotential application – optical direct brain stimulation.

With similar red LEDs already produced, “we plan to demonstrate a full-colour micro LED display in smart watch sizes by the end of this year,” said researcher Professor Keon Jae Lee.

The reason simultaneous transfer is emphasised, is that making large TV-style displays with inorganic micro-LEDs will be extremely expensive if they have to be picked-and-places one-at-a-time.

“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,” said KAIST.

The work is described in ‘Monolithic flexible vertical GaN light‐emitting diodes for a transparent wireless brain optical stimulator‘, a paper published in Advanced Materials.