ZnO Nanocrystal Thin Films for Quantum-Dot Light-Emitting Devices

Zinc oxide nanocrystals (ZnO NCs) were synthesized via a sol-gel method. After the synthesis, their surface was modified using 2,2,2-trifluoroacetic acid followed by ultraviolet (UV) treatment of the resulting fluorinated ZnO (F-ZnO) NC thin films. The chemical bonding therein and their structural and electrical properties were investigated. Moreover, the oxygen vacancy and electroluminescence properties of the densified ZnO NCs were evaluated. The effects of both UV treatment and fluorination on the morphological and electrical characteristics of the F-ZnO NC thin films were established. Based on the results, the ligand on the NCs was decomposed, and the thin film was densified. The mobility of the UV-treated F-ZnO NC thin film, which is 20.48 cm2·V-1·s-1, is four orders higher than the pristine ZnO NC thin film. By UV irradiation, the recombination of oxygen vacancies in ZnO was controlled. With the oxygen vacancies decreased, the core electroluminescence of ZnO was enhanced and the band gap of the ZnO NCs was widened from 3.25 to 3.51 eV. Therefore, the core electroluminescence of ZnO was enhanced while the interlayer emission was decreased for quantum-dot light-emitting device applications.