Optimizing Charge Balance in Quantum Dot Light-Emitting Diodes through Benzoic Acid-Passivated ZnO Nanoparticle Layers

ZnO nanoparticles (ZnO NPs) are widely utilized as electron transport layers (ETLs) in quantum dot light-emitting diodes (QLEDs) due to their high electron mobility, wide bandgap, excellent transparency, and effective hole-blocking properties. However, their high electron mobility can lead to charge imbalance and increased leakage currents, while surface defects contribute to exciton quenching at the interface with the emissive layer (EML), limiting the overall device performance. In this study, 4-CF3BA ligands were employed to effectively passivate surface defects in ZnO NPs, reducing exciton quenching and optimizing charge transport dynamics in QLEDs. This passivation strategy resulted in a significant improvement in device performance, achieving an external quantum efficiency (EQE) of 23%. The performance improvement is attributed to the suppression of interface quenching through defect passivation, improved charge balance, and enhanced electron injection. These findings demonstrate the potential of 4-(trifluoromethyl)benzoic acid (4-CF3BA) passivation as a promising approach to improve the efficiency of QLEDs, opening the way for next-generation optoelectronic device applications.