Electrohydrodynamic-Jet Sprayed Quantum Dots for Solution-Processed QD Light-Emitting-Diodes

Quantum dots (QDs) are superior to organic luminescent materials because of their inherent luminescent properties, including narrow spectral emission bandwidths, broad absorption, high photoluminescence quantum efficiency, good photo stability, controllable bandgap (through size tuning), and compatibility with solution processing. More recently, inkjet, contact printing, and mist deposition processes have been proposed as alternative methods for QDs patterning; however, they produce a non-uniform film with a rough surface morphology. Electrohydrodynamic jetting (EHD-jet) can be used for continuous patterning, drop-on-demand printing, jetting or atomization, which has numerous applications in inkjet printing technology, bio-applications, mass spectrometry, and thin film deposition. In this study, quantum dot patterns were fabricated by an EHD-jet printing process. Moreover, the parameters of the EHD-jet printing process, including the flow rate; X, Y, and Z-gap; voltage; and printing speed, were controlled precisely to produce QD thin films with a range of surface characteristics. Based on that value and new spraying methods, high-quality QD-LEDs devices were prepared with an emitting layer sprayed by EHD-jet printing.