Micro-OLED strips promise tunable white

October 27, 2016 //By Julien Happich
Using a simple and up-scalable orthogonal photo-patterning technique they had demonstrated in prior research, a team of German researchers from Dresden's Integrated Center for Applied Physics and Photonic Materials (IAPP) and the Institute for Applied Physics have designed a two-color OLED device that can be tuned from blue to white to yellow seamlessly.

Rather than stack multiple monochrome OLED layers vertically (compromising on individual colour efficiencies), they opted for alternating strips of yellow and blue p-i-n OLEDs, aligned side by side and as narrow as 20μm. A key improvement in the lateral colour mixing is the use of fine orthogonal photolithography techniques, which they say don't suffer the resolution and substrate size limitations of fine metal masks typically used for patterning. Because they are able to align the OLED strips completely adjacent, with no gaps between them, the overall OLED emits across the full panel's surface, without any dark areas between units hence improving overall luminance.

Publishing their results in Nature's Light: Science & Applications journal in the paper "Adjustable white-light emission from a photo-structured micro-OLED array", the researchers experimented with several micro-array dimensions, alternating strips of efficient fluorescent blue and phosphorescent yellow monochrome devices with different width ratios, varying from 50/50, 80/80, 80/20 and 100/30μm for the yellow/blue subunits.