Electrohydrodynamic Printing Enables Ultrahigh Resolution Quantum Dot Light-Emitting Diodes

Electrohydrodynamic (EHD) printing is a promising method for manufacturing high-resolution quantum dot light-emitting diodes (QLEDs). The stability of the EHD printing process and the morphology of final quantum dot (QD) film are highly dependent on the ink formulation. To solve this problem, we selected a ternary solvent (decahydronaphthalene, tetradecane and nonane) ink for cadmium-based QDs (CdSe/ZnS) to achieve excellent QD dispersion while eliminating the "coffee ring" effect, resulting in high quality QD films. We also fabricated a complete QLED device by printing a light-emitting layer formed by linearly aligned strips of QDs, achieving an external quantum efficiency (EQE) of 19.2 %, which is one of the highest levels of printing devices. On this basis, we introduced patterned PMMA structures prepared by nanoimprinting method to achieve ultrahigh resolu-tion devices. The pixel density achieved was 8,758 pixels per inch (PPI), with a maximum EQE of 10.5 %. The luminance is 9530.43 cd/m2 at a voltage of 4 volts. This work shows promising potential in realizing ultra-high resolution and high-performance QLEDs.