Dipole Decoration of ZnO Nanoparticle-Based Electron Transport Layer for Efficient Electron Injection in Quantum Dot Light-Emitting Diodes

Charge transport represents a critical determinant for achieving high-performance quantum dot light-emitting diodes. In conventional sandwich-structured devices, interfacial state formation due to mismatched material properties across functional layers compromises carrier transport and recombination dynamics. Here, we demonstrate a surface state engineering strategy for ZnO nanoparticles (NPs)-based electron transport layers (ETLs) via sequential ozone treatment and 2-hexanol spin coating. Solution-prepared ZnO NPs possess a large surface area and abundant surface defect states. This approach achieves atomic-scale modification of the ETL/quantum dot (QD) interface without introducing additional dielectric layers, thereby mitigating carrier loss from the defect states. The results reveal that anchored 2-hexanol molecules reconfigure the surface dipole moment of the ZnO NP film, introducing an elevated vacuum level alignment, which facilitates efficient electron injection while concomitantly suppressing exciton quenching at the ETL/QD interface. The optimized device achieves an 11% improvement in the device’s maximum power efficiency (from 16.1 to 17.9 lm/W) and about 3-fold extension in operational lifetime (from 8 to 26 h) at an initial luminance of 2000 cd/m2. This surface modification strategy for ZnO NPs highlights the significance of ETL/QD interface engineering and provides a feasible solution for device optimization.