Enhanced Performance of Pixelated Quantum Dot Light-Emitting Diodes by Inkjet Printing of Quantum Dot-Polymer Composites

Abstract

Inkjet printing of colloidal quantum dots (QDs) is considered a promising technology for application in full-color quantum dot light-emitting diode (QLED) displays. However, QLEDs that are inkjet printed in a pixel-defining bank structure generally exhibit a low performance, mainly due to the nonuniformity in its QD morphology. In this study, an enhanced performance of inkjet-printing-based pixelated QLEDs is achieved by introducing small amounts of poly(methyl methacrylate) (PMMA) of different molecular weights into QD inks. When this QD-PMMA composite ink is adopted, uniform droplets are formed, originating from contact line depinning during drying. Inside the bank structure, the inkjet-printed QD-PMMA composite film shows a smooth surface and little pileup at the bank edges. A pixelated QLED with PMMA with a molecular weight of 8 kDa exhibits the highest luminance of 73 360 cd m(-2) and an external quantum efficiency of 2.8%, which are remarkably higher than that of the inkjet-printed QLED subpixels without PMMA. The result is verified through the observation of the drying process and the QLED subpixel shapes under operation. Thus, inkjet-printed QD-PMMA composite inks can be a promising strategy for future research on pixelated QLEDs for the fabrication process of full-color QLED displays.