European project aims at 2300ppi OLED microdisplays

January 09, 2017 // By Julien Happich
Launched in January 2015 and led by scientists at the Fraunhofer FEP, the EU-funded H2020 project LOMID (Large cost-effective OLED microdisplays and their applications) aims to develop a new generation of large area OLED microdisplays which will focus on both virtual-reality (VR) and augmented-reality (AR) applications, including visual prosthetics. The project will be running until the very end of 2017.

Partners of the LOMID project aim to manufacture flexible OLED microdisplays of exceptionally large area (13×21mm) with a screen diagonal of 24.9mm at acceptable yields, over 60%.

The European consortium aims to achieve this by developing a robust silicon-based chip design supporting both high resolution (1200×1920 - WUXGA) with pixel sizes of 11µm×11µm for a pixel density of 2300 ppi, and a highly reliable manufacturing process for the backplane.

“Economical processes (e.g. based on 0.18 and 0.35 µm lithography) are being developed at the CMOS silicon foundry and special attention will be given to the interface between the top metal electrode of the CMOS backplane and the subsequent OLED layers. In order to keep the CMOS manufacturing at low cost, numerous design rules have been pushed to their limits” said Mike Thieme, project manager at LOMID contributor X-FAB.

Additional challenges such as conformability of the OLED microdisplays will be addressed to allow a bending radius of 50 mm. Along with these new functionalities, the durability of the devices when bent has to be guaranteed and be comparable to that of rigid devices.

This will be addressed by improving the OLED robustness and by modifying the device encapsulation to simultaneously fulfill stringent barrier requirements (WVTR < 10 -6 g/d m 2) and to provide sufficient mechanical protection.

Partners in the LOMID project include X-FAB Dresden GmbH & Co. KG who will manufacture the CMOS backplane wafers to be used by MicroOLED S.A.S. for OLED microdisplay fabrication. These microdisplays will be applied by Limbak SL for virtual reality glasses. The research organization CEA-Leti develops processes to realize the bendability and an appropriate encapsulation, while Fraunhofer FEP focuses on the IC design of the CMOS wafer. The University of Leipzig works on inorganic transparent FET materials, and the University of Oxford develops prosthetics for people with impaired vision. The company Amanuensis is assisting the consortium with coordination, dissemination and exploitation activities.

First prototypes