Effect of Time-Dependent Characteristics of ZnO Nanoparticles Electron Transport Layer Improved by Intense-Pulsed Light Post-Treatment on Hole-Electron Injection Balance of Quantum-Dot Light-Emitting Diodes

Abstract

We investigated the effect of intense-pulsed light (IPL) post-treatment on the time-dependent characteristics of ZnO nanoparticles (NPs) used as an electron transport layer (ETL) of quantum-dot light-emitting diodes (QLEDs). The time-dependent characteristics of the charge injection balance in QLEDs was observed by fabrication and analysis of single carrier devices (SCDs), and it was confirmed that the time-dependent characteristics of the ZnO NPs affect the device characteristics of QLEDs. Stabilization of the ZnO NPs film properties for improvement of the charge injection balance in QLEDs was achieved by controlling the current density characteristics via filling of the oxygen vacancies by IPL post-treatment.

Residual-Solvent-Induced Morphological Transformation by Intense Pulsed Light on Spin-Coated and Inkjet-Printed ZnO NP Films for Quantum-Dot Light-Emitting Diodes

“…In our previous study, we dealt with an oxygen vacancy (V O ) control scheme for the ZnO NP ETL realized by an IPL post-treatment . With this process, trapping caused by V O − and the change in the carrier concentration , in the ZnO NP ETL can be suppressed as much as possible such that how the performance of the device changes over time can be analyzed more objectively.…”

“…This was followed by annealing at N 2 for 60 °C for 30 min. Next, an IPL post-treatment under conditions identical to those in our previous research 22 was conducted to control the oxygen vacancies (V O ) in the ZnO NP ETL before the deposition of the cathode electrode. Finally, an aluminum (Al) cathode was deposited at 2 Å/s to a thickness of 100 nm by thermal evaporation under a high vacuum pressure of 2 × 10 −7 Torr.…”

“…In this study, we formed a ZnO NP film, which has recently attracted the most attention as an ETL of QLEDs, − by means of both spin coating and inkjet printing and investigated the morphological tendencies of the film surface according to the annealing condition. In addition to the previously studied IPL post-treatment, morphological changes to the ZnO NP film surfaces were also closely analyzed, and we observed that the ZnO NP films form four types of surface morphologies depending on the annealing condition and/or the presence of annealing. Finally, it was confirmed that three final surface shapes in total were formed.…”

A review on intense pulsed light process as post-treatment for metal oxide thin films and nanostructures for device application

“…The effect of IPL sintering on ZnO ETL was reported for QLEDs. The authors did the IPL post-treatment not on a single layer of ZnO nanoparticles, but on a multi-layer coated with various materials as shown in figure 13(a) [116]. The XPS spectrum demonstrated that the oxygen vacancy in the ZnO lattice was filled with oxygen by IPL (figure 13(b)).…”

Dual-Facets Emissive Quantum-Dot Light-Emitting Diode Based on AZO Electrode

“…Since the first report of the quantum-dot light-emitting diode (QLED), it has attracted increasingly more attention for merits of their properties, such as high photoluminescence (PL), quantum yield (QY), tunable colors, saturated color emission, narrow emission with full-width at half-maximum (FWHM), solution processability, and process compatibility [1][2][3][4][5]. QLEDs can be expanded to high-volume applications toward commercialization, such as liquid-crystal display backlights [6] and solid-state displays and lighting [7][8][9].…”