Pixel-Level Electrostatic Engineering via Inkjet-Printed Self-Assembled Monolayers in InP Quantum-Dot Light-Emitting Diodes

초록

Inkjet printing enables scalable, mask-free fabrication of quantum dot light-emitting devices, yet precise electrostatic control at printed oxide/quantum dot interfaces remains a major challenge for high-resolution displays. In inverted InP quantum dot light-emitting diodes (QLEDs), shallow-work-function oxide electron transport layers cause excessive electron injection, leading to charge imbalance, interfacial carrier accumulation, and efficiency roll-off. Here, we present an inkjet-printing-based digital patterning strategy that enables pixel-level electron-injection control by spatially programming interfacial dipoles on a 200 ppi pixelated substrate. Octadecylphosphonic acid (ODPA) is selectively deposited onto printed ZnMgO nanoparticle electron transport layers, forming an ODPA-containing phosphonate interfacial layer within defined pixel regions. The resulting dipole formation and modification of oxygen-vacancy-related surface states raise the surface work function by similar to 0.08 eV and alter the interface-sensitive electron-transport behavior. This interfacial modification suppresses electron over-injection and improves charge balance without increasing the turn-on voltage. Consequently, the optimized devices exhibit enhanced external quantum efficiency and reduced efficiency roll-off. These results establish inkjet-patterned molecular dipoles as digitally addressable electrostatic building blocks for pixel-level charge regulation in printed optoelectronics.

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