A cracking-assisted transfer printing technology for high-resolution quantum dot light-emitting diode displays

Abstract

Inorganic colloidal quantum dot light-emitting diodes could be used to build next-generation electroluminescent displays due to their colour properties and electrical stability. However, to create high-resolution and large-area displays, a pixel integration method is required, which can deposit quantum dot arrays on an active-matrix backplane and maintain uniformity and precision, without colour cross-contamination. Here we report a cracking-assisted transfer printing technology that can be used to pattern high-resolution full-colour pixel arrays over large areas. The technology uses a controlled cracking process to fracture interparticle cohesive bonds between quantum dots. This facilitates subsequent pick-up and transfer to a thin-film transistor backplane with high precision. With the technology, we achieve pixels down to a size of 600 nm with electroluminescent emission and uniform pixelization over areas up to 4 inches. We create a cadmium-free full-colour active-matrix display with a resolution of 341 pixels per inch, as well as a blue active-matrix display with a flexible form factor. Furthermore, the cracking-assisted transfer printing can improve electroluminescence performance—with higher maximum luminance and operational lifetime than other quantum dot patterning techniques—through precise nano-interface control and high quantum dot packing density. Quantum dot pixel arrays can be transfer printed over areas up to 4 inches, and with pixel sizes down to 600 nm, using a cracking step to fracture the cohesive bonds between dots before pick-up and transfer.