Ultrasonic spray coating as deposition technique for the light-emitting layer in polymer LEDs

In this work the ultrasonic spray coating technique is introduced as an alternative wet solution process for the deposition of the (Super Yellow) light-emitting layer for polymer light-emitting diodes (PLEDs). An investigation on the use of this coating technique in ambient conditions is performed and a comparison with spin coated PLEDs in inert atmosphere is made. Uniform low roughness thin films with a typical thickness of 80 nm are obtained by varying the polymer-solvent mixture and spray coater parameters. PLEDs are produced and reach a luminous power efficacy in the order of 10 lm/W. Through the use of various optical and analytical techniques it is demonstrated that the applied ultrasonic atomization has no noteworthy influence on the original properties of the polymer and on the resulting PLED's efficacy. Ultrasonic spray coating is therefore a viable deposition technique for the production of PLEDs. (C) 2015 Elsevier B.V. All rights reserved.