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.

Perovskite light-emitting diodes (PeLEDs) are attracting increasing attention owing to their impressive efficiencies and high luminance across the full visible light range. Further improvement of the external quantum efficiency (EQE) of planar PeLEDs is limited by the light out-coupling efficiency. Introducing perovskite emitters with directional emission in PeLEDs is an effective way to improve light extraction. Here, we report that it is possible to achieve directional emission in mixed-dimensional perovskites by controlling the orientation of the emissive center in the film. Multiple characterization methods suggest that our mixed-dimensional perovskite film shows highly orientated transition dipole moments (TDMs) with the horizontal ratio of over 88%, substantially higher than that of the isotropic emitters. The horizontally dominated TDMs lead to PeLEDs with exceptional high light out-coupling efficiency of over 32%, enabling a high EQE of 18.2%.