Roughening the white OLED substrate's surface through sandblasting to improve the external quantum efficiency

A simple, low cost, and scalable process based on sandblasting to modify the OLED substrate's surface, has been successfully developed. The rough surface produced by sandblasting efficiently suppressed the internally generated photons' waveguide mode, and enhanced the white OLED's EQE from 9% to 11.6% without changing the emission spectrum and the Lambertian emitter property. The improvement of the EQE was found to monotonically decrease with the surface roughness within the roughness range from around 1 mu m to 3 mu m. The white OLED's luminous efficiency was increased from 15.5 cd A(-1) to 20 cd A(-1). Furthermore, the realization of rough surface on a 3.5 inch white lighting panel not only improved the 9-point uniformity from 80% to 90%, but also demonstrated the manufacturing scalability of the sandblasting technique. (C) 2011 Elsevier B.V. All rights reserved.