Inverted structural quantum dot light-emitting diodes based on Al-doped ZnO electrode

Abstract

As an indium-free transparent conducting film, Al-doped zinc oxide (AZO) was prepared by magnetron sputtering technique, exhibiting good electrical, optical and surface characteristics. UPS/XPS measurements show that AZO and zinc oxide nanoparticles (ZnO NPs) have matched energy level that can facilitate the electron injection from AZO to ZnO NPs. Inverted structural green quantum dot light-emitting diodes based on AZO cathode were fabricated, which exhibits a maximum luminance up to 178 000 cd m, and a maximum current efficiency of 10.1 cd A. Therewith, combined with the simulated space-charge-limited current (SCLC) theory, the measured current density-voltage characteristics of charge-only devices were analyzed. It demonstrated that AZO and ZnO NPs had much better electron injection efficiency than ITO, showing a electron injection efficiency close to 100%. By studying the relationship between the electric field and the current density, the measured curve of AZO-based devices nearly fits the theoretical curve of SCLC and the AZO electrode has a better ohmic contact with ZnO NPs than ITO.

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

“…However, reports about QLEDs based on AZO cathodes are rare. It has been reported that AZO electrodes have a better ohmic contact with ZnO NPs than ITO [17]. As a result, it is considered in the design of dual emissive devices based on AZO cathodes, which is deposited on ZnO NPs.…”

Quantum dot light-emitting diodes with an Al-doped ZnO anode

“…Additionally, the optical and electrical performance of an AZO film prepared by the MS method can also be adjusted by varying the sputtering pressures, sputtering power, Ar flow rate, doping concentration, substrate temperature, etc [28][29][30]. Due to the excellent performance of AZO, it has been used in the applications of solar cells, organic light-emitting diodes (OLEDs), and other optoelectronic devices [19,20,[31][32][33]. As commonly seen in OLEDs [19], an AZO electrode can avoid the diffusion of indium elements into the device; thus, a similar effect can be expected in QLEDs.…”

“…As commonly seen in OLEDs [19], an AZO electrode can avoid the diffusion of indium elements into the device; thus, a similar effect can be expected in QLEDs. In QLEDs, for example, Lin et al constructed an inverted green QLED device based on AZO electrodes by the DC MS method, in which the maximum EQE reached 2.3% at an emission peak at 535 nm [32] A smooth and flat surface electrode is the key factor in constructing QLEDs to produce a homogeneous charge carrier injection and electric field, and high performance [34][35][36]. For instance, Wolff et al [34] discussed the relationship between the turn-on voltage of QLED performance and the graphene roughness.…”