A Novel Blade-Jet Coating Method for Achieving Ultrathin, Uniform Film toward All-Solution-Processed Large-Area Organic Light-Emitting Diodes

Abstract

This paper reports a new type of large-area solution coating method that combines a blade coating process and an air-jet finishing process, and its application to soluble organic light-emitting diodes (OLEDs) fabrication. The blade coating with stable coating conditions results in a relatively thick uniform wet film. Air-jet finishing subsequently adjusts the wet film to the target thickness by precisely controlling the flow of the coating solution. By hybridizing the blade coating method and air-jet finishing technique, functional thin-film layers can be produced with outstanding quality in terms of thickness uniformity and controllability with high reproducibility. In particular, the blade-jet coating method enables the fabrication of an ultrathin electron injection layer (EIL) of Cs2CO3 at less than a few nanometer scale over a large area by a solution process. The superior performance of the blade-jet coating method enables solution-processed large-area OLED fabrication on both rigid and flexible substrates, with outstanding light-emitting uniformity. Furthermore, by controlling the thickness and interfacial properties of the EIL, device performance can be optimized. The luminous power efficiency of the optimum OLED device is 8.42 lm W-1, and the luminous nonuniformity is only 2.68% at 6 V over a large area.