Direct Writing High-Resolution Quantum Dot Micro-Patterns: Toward High-Performance Electroluminescence Behavior.

Abstract

The fabrication of quantum dots (QDs) micro-patterns, especially those with both µm-scale high-resolution and mm-/cm- scale large area uniformity, remains a bottleneck limiting the application of quantum dot light-emitting diodes (QLEDs). Current strategies have suffered from either low resolution or complicated micro-template assisted fabrications deteriorating the device performance. Here, we developed a new conceptual high-resolution QDs micro-pattern with a linewidth of merely 2 µm in an area of ∼10 cm² by a template-free direct writing strategy, featured as the distinguishable QDs micro-line array by the periodical nanoscale thickness difference. The enhanced capillary flow accelerates QDs deposition at each tri-phase contact line in a positive feedback manner until the liquid film breaking, which proceeds uniformly across the whole printing area in a good periodicity. Thus, a periodic conformal complementary QDs/PMMA heterostructure bilayer film, composed of alternate thick-QDs/thin-PMMA and thin-QDs/thick-PMMA unit, was constructed as the light-emitting layer, which facilitates the autonomous charge distribution at both inter- and intra- interface. The as-developed high-resolution micro-patterned QLED shows an external quantum efficiency as high as 21.4% even at a linewidth of 2 µm. The result offers a low-cost facile strategy for making large-area high-resolution micro-patterned QLED devices.