High Performance Top-Emission Quantum Dot Light-Emitting Diodes with Mg-Doped ZnO Nanoparticles Used as an Electron Transport Layer

Abstract

In this paper, we reported superior performance of solution-processed top-emission quantum dot light-emitting diodes (TE-QLEDs) with Mg-doped ZnO nanoparticle (NP) electron transport layer (ETL). The Mg-doped ZnO NPs were synthesized by the sol-gel method. Transmission electron microscopy (TEM) analysis of the Mg-doped ZnO NPs with 0 wt%, 5 wt%, 10 wt%, and 15 wt% Mg-doping concentrations revealed average diameters of 5.86 nm, 5.33 nm, 4.52 nm, and 4.37 nm, respectively. The maximum luminance, the current efficiency, and external quantum efficiency (EQE) were 178,561.8 cd/m2, 56.0 cd/A, and 14.43%, respectively. However, for the best performance of TE-QLED without Mg-doping in the ZnO NPs, the maximum luminance was only 101,523.4 cd/m2, the luminous efficiency was 27.8 cd/A, and the EQE was 6.91%. The improvement of the performance is attributed to the suppression of electron transfer by an increase in the energy barrier between the cathode and Mg-doped ZnO NP ETL and the reduction in the Hall mobility of electron with increasing the Mg-doping in the ZnO NPs, resulting in the enhanced charge balance in the quantum dot (QD) emitting layer (EML).

Effective role of Rb doping in controlling the crystallization, crystal imperfections, and microstructural and morphological features of ZnO-NPs synthesized by the sol–gel approach

“…Moreover, ZnO is an appropriate catalyst to promote photocatalytic activities and photophysical effectiveness. [10][11][12] Therefore, the study of ZnO nanostructures has attracted keen interest because of their promising physical and chemical properties and functions compared with other transition metal oxides. Zinc oxide is available in the Earth's crust as zincite, but most of the zinc oxide used commercially is synthetically prepared.…”

“…Moreover, ZnO is an appropriate catalyst to promote photocatalytic activities and photophysical effectiveness. 10–12…”

Highly Efficient and Bright Quantum‐Dot Light‐Emitting Diodes with Enhanced Charge Balance by Adjusting the Thickness of Zn0.9Mg0.1O Electron Transport Layer

“…ZnMgO NPs were synthesized by a sol-gel method according to the previous report. [30] Zinc acetate dihydrate (Zn(CH ) was stirred at room temperature for 1 h to ensure that they were fully dissolved. Heptane (Daejung) was poured into the synthesized solution to precipitate the ZnMgO NPs.…”

“…QLEDs were fabricated by a solution process. [30] We fabricated QLEDs by a solution process; the anode was formed by patterning an indium tin oxide (ITO)-coated glass substrate with a sheet resistance of ≤10 Ω/□. The ITO glass substrate was cleaned with acetone, isopropyl alcohol, methanol, and deionized water.…”

“…Here, we used the composition ratio of Zn 0.9 Mg 0.1 O as an ETL, which our group verified previously. [ 30 ] The improved charge balance is due to the reduction of electron injection caused by an increase in resistance of Zn 0.9 Mg 0.1 O NP ETL with thickness. Our research demonstrates that adjusting the thickness of Zn 0.9 Mg 0.1 O NP ETL could improve device performance.…”