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

• Published in: Advanced optical materials Vol. 9; no. 11
• Main Authors: Roh, Heebum, Ko, Donghyun, Shin, Dong Yeol, Chang, Jun Hyuk, Hahm, Donghyo, Bae, Wan Ki, Lee, Changhee, Kim, Jun Young, Kwak, Jeonghun
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.06.2021
• Subjects: Color; Displays; Drying; Inkjet printing; Inks; Materials science; Molecular weight; Morphology; Nonuniformity; Optics; Performance enhancement; Pixels; PMMA; Polymer matrix composites; Polymethyl methacrylate; QD–polymer composite; quantum dot light‐emitting diodes; Quantum dots; Quantum efficiency; subpixels
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.202002129

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. Inkjet‐printing‐based pixelated quantum dot (QD) light‐emitting diodes are demonstrated by introducing QD–polymer composite inks. The devices exhibit a maximum luminance of 73 360 cd m−2 and an external quantum efficiency of 2.8%, owing to the improved QD morphology and reduced QD pileup at the bank edges by controlling the internal flow dynamics with the addition of the polymer.