Inkjet Printing of an Electron Injection Layer: New Role of Cesium Carbonate Interlayer in Polymer OLEDs

Abstract

Among solution-processable techniques, inkjet printing is a potential method for manufacturing low-cost and high-resolution polymer organic light-emitting diodes (PLEDs) for displays/solid-state lighting applications. Herein, we demonstrate use of the inkjet printed cesium carbonate (Cs2CO3) film as an electron injection interlayer. We have elaborated the Cs2CO3 ink using an alcohol-based solvent for the industrial-grade printhead. The printed Cs2CO3 layer morphology was investigated by means of an optical microscope and an atomic force microscope. The PLEDs based on emissive polymer (Super Yellow) with printed Cs2CO3 interlayer show a remarkable current efficiency and luminance compared to the PLEDs made without the Cs2CO3 layer. Such results suggest that the Cs2CO3 is a promising material for the formulation of the electron injecting inkjet inks. The possibility of inkjet printing of an efficient electron injecting layer enables in situ patterning of PLEDs’ emission area. Such a simple and flexible technique can be applied for a wide range of applications such as signage, pictograms, advertising, smart packaging, etc.

Three Destinies of Solution-Processable Polymer Light-Emitting Diodes under Long-Time Operation

“…The stability of a model PLED based on Super Yellow-the most often used polymer as an emission layer in PLEDs [22]-has been studied in terms of the conductive-capacitive properties of the organic layers. It was found that the AC response is extremely sensitive to the minor changes in PLED caused by the applied electric field, and contact with the ambient atmosphere.…”

Performance Enhancement of Quantum Dot Light-Emitting Diodes via Surface Modification of the Emitting Layer

“…As the concentration of cesium carbonate increased, the brightness of the composite device was also improved (Figure b), which corresponded to the results obtained by PL and TRPL. At the same time, the turn-on voltage of the device was also reduced because of the excellent ability of cesium carbonate to improve electron injection. − As shown in Figure d, although an extra layer was added to the quantum dot device, the current density of the device did not decrease but increased, which further proved the good electron injection ability of cesium carbonate. Moreover, the external quantum efficiency (EQE) and power efficiency (PE) had a significant improvement (Figure S8).…”

The Impact of Technological Parameters on the Quality of Inkjet-Printed Structures

“…It is characterized by low amounts of waste and the use of a small amount of material needed for the process. Application areas for printed electronics include, so far, resistors [5], organic light-emitting diodes (OLEDs) [6], display [7], solar cells [8], thin-film transistors [9], capacitors [10,11], microwave circuits [12,13], and many others.…”