Surface‐Engineered ZnO Nanoparticles via Acetone Immersion for Charge‐Balanced High Resolution Full‐Color Organic Light Emitting Diode Displays

In solution-processed organic light-emitting diodes (OLEDs), carrier injection imbalance and interfacial quenching persist as major hurdles, primarily due to the hole-dominated transport in polymer-based emitters. Here, we introduce a simple but highly effective post-fabrication strategy for enhancing charge balance and device performance by chemically modifying ZnO nanoparticles (ZnO-NPs) through acetone immersion. This treatment selectively passivates oxygen vacancy-related trap states at the ZnO NPs surface, resulting in improved electron injection and restored hole-blocking behavior, without disrupting the device structure or layer interfaces. Comprehensive analyses, including X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and transient electroluminescence (EL) measurements, confirm the defect passivation mechanism and its impact on charge injection dynamics. Acetone-treated OLEDs exhibit reduced turn-on voltage, significantly higher luminance (exceeding 44 000 cd/m2), and enhanced efficiency across all RGB subpixels, while maintaining spectral purity. Furthermore, this method enables scalable fabrication of ultra-high-resolution RGB pixel arrays on a large scale without requiring additional functional layers.