Inkjet Printed Bilayer Light-Emitting Electrochemical Cells for Display and Lighting Applications

A new bilayer light‐emitting electrochemical cell (LEC) device, which allows well‐defined patterned light emission through an easily adjustable, mask‐free, and additive fabrication process, is reported. The bilayer stack comprises an inkjet‐printed lattice of micrometer‐sized electrolyte droplets, in a “filled” or “patterned” lattice configuration. On top of this, a thin layer of light‐emitting compound is deposited from solution. The light emission is demonstrated to originate from regions proximate to the interfaces between the inkjetted electrolyte, the light‐emitting compound, and one electrode, where bipolar electron/hole injection and electrochemical doping are facilitated by ion motion. By employing KCF3SO3 in poly(ethylene glycol) as the electrolyte, Super Yellow as the light‐emitting compound, and two air‐stabile electrodes, it is possible to realize filled lattice devices that feature uniform yellow–green light emission to the naked eye, and patterned lattice devices that deliver well‐defined and high‐contrast static messages with a pixel density of 170 PPI. A novel inkjet‐printed light‐emitting electrochemical cell (LEC), which allows for well‐defined and patterned light emission through an easily adjustable, mask‐free, and additive fabrication process, is reported. Inkjet‐printed bilayer LEC devices that feature uniform yellow‐green light emission to the naked eye, and static displays that deliver well‐defined and high‐contrast messages with a pixel density of 170 PPI, are presented.