Highly flexible organic light-emitting diodes based on ZnS/Ag/WO3 multilayer transparent electrodes

We report our study on highly flexible organic light-emitting diodes based on ZnS/Ag/WO3 (ZAW) multilayer transparent electrodes in which high conductivity and ductility of Ag layers allow for efficient sheet conduction and flexibility while ZnS and WO3 layers provide a means for enhancement in optical transmission and/or carrier-injection. Devices with ZAW anodes fabricated on planarized plastic substrates not only exhibit a performance and operational stability comparable to or better than those of ITO-based devices but also show a mechanical flexibility that is far superior to that of ITO-based devices. Experimental results show that a consistent performance can be obtained in ZAW-based devices upon repeated bending down to a radius of curvature of 5 mm, below which the flexibility of the devices is limited ultimately by the delamination occurring at cathode/organic interfaces rather than by the ZAW electrodes themselves. (C) 2009 Elsevier B.V. All rights reserved.