Printing Unifrom QDs Polymer Thin Film for QLED Applications

Abstract

The inkjet printing method is a promising deposition method to fabricate multicolor quantum dot display, multicolor micro-LED display, and solar cells. This paper presents a method to inkjet print uniform quantum dots (QDs) polymer films for multicolor QLED display applications. The challenge is to obtain uniform polymer QDs dots from the dilute polymer solution without affecting the optical properties of QDs. Polydimethylsiloxane (PDMS) was used as the base polymer combining with phenyl group-based inks as the QDs polymer ink. PDMS is one of the most widely used polymers for microlectronics due to its optical properties of high transparency and high refractive index. Furthermore, PDMS is also biocompatible, inflammable and flexible. All of these properties make PDMS very popular in wearable and flexible electronic devices. The emission peak and full width half maximum (FWHM) of polymer QDs ink are the same as those of the pure QDs ink. This reveals that the optical properties of polymer QDs ink is the same as those of pure QDs ink. The size of the printed QDs was around 19 gm without the coffee ring effect that may be due to the establishment of a solvent composition gradient. By reducing the drop spacing of printed dots, a 5x5 mm uniform polymer QDs thin film could be achieved. The thickness of the polymer QDs film can be optimized by the layer-by-layer printing structure. The luminance intensity increased with the increase of printing layers. The color coordinate value could also be optimized with the layer-by-layer printing structure. The printed QDs film proved its potential use in the multicolor display applications.