Ultrasonic Spray Coating of Silver Nanowire-Based Electrodes for Organic Light-Emitting Diodes

The expanding field of flexible organic electronics has led to a high demand for flexible, stable, and transparent electrodes that retain their conductivity at high-strain deformation. Among many transparent conductive electrodes (TCEs) of which indium tin oxide (ITO) is the most renowned, silver nanowires (AgNWs) prove to be an excellent highly conductive and transparent alternative. These 1D silver nanostructures form a flexible mesh of nanometer-thin wires that can be applied using solution-processing and printing techniques. Ultrasonic spray coating is a high-end low-cost, environmentally friendly, and roll-to-roll compatible printing technique. AgNWs with three different diameters (50, 70, and 115 nm) are ultrasonically spray coated on glass and demonstrate sheet resistances lower than 10 omega sq(-1) combined with transparencies up to 88%. Consequently, the conductive polymer poly(3,4-ethylenedioxythio-phene):poly(styrene sulfonate) (PEDOT:PSS) is ultrasonically spray coated to fill up the cavities between the AgNW mesh and to planarize the surface. The ultrasonically spray coated AgNWs/PEDOT:PSS electrodes are employed as TCEs for organic light-emitting diodes (OLEDs) showing very promising results with a luminous flux of 1.75 lm and a luminous efficacy of about 11 lm W-1 at 3 V driving voltage. Herein, ultrasonic spray coating is demonstrated as an excellent printing technique to apply AgNWs and PEDOT:PSS.