A facile approach to improve light extraction for organic light emitting diodes via azobenzene surface relief gratings

We report on synthesis of photo-crosslinkable and photo-bleachable azobenzene based polymer and a facile process for enhancement of light extraction in organic light emitting diodes (OLEDs) using azobenzene surface relief gratings (SRGs). The crosslinked and bleached azobenzene SRGs were achieved using a two-step photo-induced fabrication process. The bleached azobenzene SRGs showed improvement in transmittance in the visible region compared with unbleached azobenzene SRGs. The SRGs were applied to OLEDs based on tris(8-hydroxyquinoline) aluminum(III) (Alq₃) and poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV). As a result, the luminance of both OLEDs was increased by 18% through the use of transparent SRGs.