High‐Resolution Patterning via Electrohydrodynamic (EHD)‐Jet Printing for Quantum Dot Light‐Emitting Diodes

ABSTRACT High‐resolution printing technology is crucial for electroluminescent (EL) quantum dot light‐emitting diodes (QD‐LEDs) to be used in high‐end display applications such as AR/VR displays. This study successfully demonstrates the patterning of PEDOT:PSS, ZnO nanoparticles (NPs), and InP‐based QD/organic nanohybrids using electrohydrodynamic (EHD)‐jet printing, fabricating top‐emitting green conventional or inverted QD‐LEDs on a PEN flexible substrate. The integration of a hydrophobic pixel defining layer and continuous‐jet modes in the EHD‐jet printing system enhances the patterning processability, showcasing the EL of patterned conventional and inverted QD‐LEDs. Especially, the EL spectrum of an inverted QD‐LED exhibits a sharp green emission at a peak wavelength of 542 nm, with a full width at half maximum (FWHM) of 46 nm. This indicates that the uniform layers were achieved through EHD‐jet printing and balanced charge carriers in the device, despite the active layer consisting of not only InP‐based QDs but also n‐type and/or p‐type organic transport materials. This research opens up new possibilities for the utilization of EHD‐jet printing in various QD‐LED structures for commercially viable printed display applications.