High‐Resolution Inkjet Printing of Quantum Dot Light‐Emitting Microdiode Arrays

The direct printing of microscale quantum dot light‐emitting diodes (QLEDs) is a cost‐effective alternative to the placement of pre‐formed LEDs. The quality of printed QLEDs currently is limited by nonuniformities in droplet formation, wetting, and drying during inkjet printing. Here, optimal ink formulation which can suppress nonuniformities at the pixel and array levels is demonstrated. A solvent mixture is used to tune the ejected droplet size, ensure wetting, and provoke Marangoni flows that prevent coffee stain rings. Arrays of green QLED devices are printed at a resolution of 500 pixels in.−1 with a maximum luminance of ≈3000 cd m−2 and a peak current efficiency of 2.8 cd A−1. The resulting array quality is sufficient to print displays at state‐of‐the‐art resolutions. High‐resolution functional quantum dot pixels for displaying can be realized by inkjet printing. The ink formulation is the vital factor, in order to tune droplet formation, wetting, and pixel drying. The underlying mechanisms are discussed separately and combined to enable high‐resolution devices.