Scattering Structure in Flexible Substrate for Light Extraction of Organic Light-Emitting Diodes

Abstract

In this work, we demonstrate low-cost and simple way to produce flexible light extraction substrate for enhancing out-coupling efficiency. We achieve flexible hazy substrate by introducing scattering structure in polymer substrate with oxygen plasma etching and planarization coating on etched surface. Flexible hazy substrate using PET shows average haze of 68.4% preserving high average total transmittance of 90.3% similar with bare PET. And this haze can be controlled by plasma etching time. Also, these optical properties are maintained through bending cycle test up to 10,000 cycles with bending radius of 4 mm. Furthermore, planarization coating reduces surface roughness of Ra effectively from etched substrate of 430 nm to coated substrate of 4 nm. With this flexible haze substrate, power efficiency of OLEDs is increased by 22% and it is further enhanced by 91% when external pattern layer for light extraction is applied.