Lambertian Extraction of Light from Organic Light-Emitting Devices Using Randomly Dispersed Sub-Wavelength Pillar Arrays.

A simple light extraction method is reported to minimize the variation in emission spectrum with viewing angle by embedding a light extraction layer, consists of randomly dispersed nano-pillars on a substrate. Nano-imprint lithography technique was employed to fabricate the nano-pillars using ultra-violet curable acrylate. An organic light emitting diode device employing the imprint technology showed 46% enhancement in light extraction efficiency in the forward direction with Lambertian emission pattern and no color change with viewing angle. Moreover, the emitted light does not show any specific periodic patterns.