Single mode waveguiding effect of ZnO nanorods to enhance the luminance of conjugated polymer based light emitting diodes

In the present work, a unique strategy to improve light emission from poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) based polymer light emitting diodes (PLEDs) has been reported. It was observed that integration of vertical ZnO nanorods (NRs) in the PLED structure drastically enhances the luminance (more than 20 times) as compared to that of basic MEH-PPV device. The analysis reveals that the waveguiding effect of NR structure is responsible for this phenominal enhancement. ZnO NRs possess large acceptance angle and are able to direct the collected light perpendicular to the ITO plane through single mode propagation. This rectifies the problem of undesired total internal reflection at ITO/glass and glass/air interfaces, which is the root cause of reduced light extraction from PLEDs.