High-resolution patterning of colloidal quantum dots via non-destructive, light-driven ligand crosslinking

Jeehye Yang,Myeongjae Lee,Jun Hyuk Chang,Hye Won Park,Minkyoung Lee,Bongsoo Kim,Wan Ki Bae,Joohee Bang,Seunghan Kim,Donghyo Hahm,Jeonghun Kwak,Hyeokjun Kim,Kyunghwan Kim,Seunghyun Rhee,Moon Sung Kang,Jeong Ho Cho,Changhee Lee,Hyungju Ahn,Jaehoon Lim

doi:10.1038/s41467-020-16652-4

Abstract

Establishing multi-colour patterning technology for colloidal quantum dots is critical for realising high-resolution displays based on the material. Here, we report a solution-based processing method to form patterns of quantum dots using a light-driven ligand crosslinker, ethane-1,2-diyl bis(4-azido-2,3,5,6-tetrafluorobenzoate). The crosslinker with two azide end groups can interlock the ligands of neighbouring quantum dots upon exposure to UV, yielding chemically robust quantum dot films. Exploiting the light-driven crosslinking process, different colour CdSe-based core-shell quantum dots can be photo-patterned; quantum dot patterns of red, green and blue primary colours with a sub-pixel size of 4 μm × 16 μm, corresponding to a resolution of >1400 pixels per inch, are demonstrated. The process is non-destructive, such that photoluminescence and electroluminescence characteristics of quantum dot films are preserved after crosslinking. We demonstrate that red crosslinked quantum dot light-emitting diodes exhibiting an external quantum efficiency as high as 14.6% can be obtained.

Highlights

Establishing multi-colour patterning technology for colloidal quantum dots is critical for realising high-resolution displays based on the material
The challenge arises from the fact that quantum dots (QDs) are processed from solutions, unlike organic luminophores used for organic light-emitting diode (OLED) that are typically processed by thermal evaporation[23,24,25]
The crosslinker with two fluorinated phenyl azide terminals is intended to undergo C–H insertion reaction into the long aliphatic chains of the ligands that passivate the surface of QDs

Summary

Introduction

Establishing multi-colour patterning technology for colloidal quantum dots is critical for realising high-resolution displays based on the material. Colloidal quantum dots (QDs), nanocrystalline semiconductors with dimensions residing in the quantum confinement regime[1,2,3,4], exhibit ultrahigh colour purity and near-unity luminescence quantum yield[5,6,7] These excellent characteristics of QDs have led the materials to be successfully incorporated into commercial display devices, positioned to challenge organic light-emitting diode (OLED) technology. As the resulting crosslinked QD films are structurally robust against subsequent solution processes, multiple patterns of QDs can be formed through consecutive cycles of solution-based film deposition and photo-patterning processes Based on this strategy, we successfully fabricate QD line patterns with a minimum feature size of 3 μm and RGB QD patterns with a sub-pixel size of 4 μm × 16 μm that corresponds to a resolution of >1400 pixels per inch (p.p.i.). The simple strategy presented here will make a significant impact on the production of highresolution, large area, full-colour QD-LEDs, which are intensively explored across the scientific community to industry

Methods

Results

Conclusion