Self-Assembled Monolayer InP Quantum Dots for Direct Photolithographic High-Resolution Light-Emitting Devices

The photolithographic patterning of heavy-metal-free InP quantum dots (QDs) is of significance for applications in high-resolution displays. Light-driven direct cross-linking of ligands from adjacent QDs, without introducing insulating photoresist, is a feasible strategy. Nonetheless, the randomly arranged, loosely stacked QDs generated by traditional deposition present significant interstitial voids, which hinder the effective cross-linking of ligands. In this study, close-packed monolayer InP QDs are assembled utilizing Langmuir-Blodgett (LB) technology to facilitate robust cross-linking. The QDs arranged side by side, followed by the photo-cross-linking process, demonstrate superior resistance to the developing process compared to those derived from spin-coated (SC) films. InP QD light-emitting diodes (QLEDs) with finely patterned pixels (average size of 3 μm × 3 μm) have been successfully fabricated, achieving a resolution exceeding 4000 pixels per inch. Additionally, the patterned monolayer QLEDs exhibit a high external quantum efficiency of 9.56%, considerably outperforming those of SC-based devices (4.99%). This work presents a promising approach for the lithographic fabrication of environment-friendly QLEDs.