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

ABSTRACT 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 ∼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.