Grey-scale OLED patterns reach 12,700 dpi resolution

May 03, 2016 // By Julien Happich
Researchers from Fraunhofer FEP have successfully used e-beams to pattern the emission area of an OLED, forming permanent high resolution grey-scale images.

The electron beam process is performed after finalizing the OLED panels, including the encapsulation, hence leveraging the volume production of un-patterned OLEDs before individually modifying the emission characteristics of the active layers, at a pixel pitch down to 2µm.

The energy of the electrons determines their penetration depth in the layer stack. With a suitable choice of process parameters, the encapsulation can also be penetrated by the electron beam and the luminous characteristics of the organic layers beneath will change without destroying or compromising the encapsulation itself, the researchers report. Depending on the application, it is even possible to modify individual layers directly.

"This fixed image writing achieves resolutions way beyond what could be achieved through OLED layer deposition, achieving continuous grey-scale rather than a binary on-off OLED state", told EETimes Europe, Elisabeth Bodenstein from the development team at Fraunhofer FEP.

Compared to overlay dimming alternatives, often consisting of a sticker or a screen-printed mask on top of the fully lit OLED, the new process allows very fine and permanent watermarking of any production OLED, while reducing the power consumption of the OLED. "This is because the dimmed pixels consume less as their resistance is increased by the e-beam process", clarified Bodenstein.