High-resolution and high-efficiency micro quantum-dot light-emitting diode arrays via conventional photolithography

Quantum-dot light-emitting diodes (QLEDs) promise a new generation of low-cost, efficient, bright, and stable light sources. Achieving large-area patterning of high-resolution QLED arrays is essential for display applications. However, patterning of micro-QLEDs arrays via conventional photolithography, the most established and scalable technique capable of producing micrometer-scale patterns, poses challenges because the chemicals and solvents used can damage quantum dot emissive layers and charge transport layers (CTLs) during ultraviolet (UV) exposure and development. Here, we address these challenges by designing a novel hole transport layer (HTL), poly((9,9-dioctylfluorenyl-2,7-diyl)-co-(9-(2-ethylhexyl)-carbazole-3,6-diyl)-co-(9-(4-(4-vinylphenoxy)butyl)-carbazole-3,6-diyl)) (PF8Cz-X), which replaces reactive triphenylamine (TPA) units with chemically stable carbazole derivatives and introduces vinylphenoxy groups that crosslink upon annealing, enhancing solvent resistance. Utilizing PF8Cz-X, we fabricated efficient and high-resolution micro-QLEDs arrays with pixel sizes down to ~ 2 μm, achieving resolutions up to 6000 pixels per inch. The red, green, and blue micro-QLEDs demonstrate peak external quantum efficiencies (EQEs) of 16.5%, 20.1%, and 12.7%, respectively, matching those of un-patterned devices. Our work reveals that conventional photolithography can be effectively employed for the fabrication of high-resolution micro-QLEDs array, paving the way towards advanced display applications in augmented reality (AR) and virtual reality (VR) technologies.