Application of solution-processed metal oxide layers as charge transport layers for CdSe/ZnS quantum-dot LEDs

Abstract

We fabricated and characterized quantum-dot light emitting devices (QLEDs) that consisted of a CdSe/ZnS quantum-dot (QD) emitting layer, a hole-transporting nickel oxide (NiO) layer and/or an electron-transporting zinc oxide (ZnO) layer. Both the p-type NiO and n-type ZnO layers were formed by using sol-gel processes. All the fabricated CdSe/ZnS QLEDs showed similar electroluminescence spectra that originated from the green CdSe/ZnS QDs. However, different combinations of hole- and electron-transporting layers resulted in efficiency variations. In addition to the control of the respective concentrations of holes and electrons within a multilayer device structure, which determines the luminance and efficiency of QLEDs, the use of metal oxide layers is advantageous for long-term stability of QLEDs because they are air stable and can block the permeation of water vapor and oxygen in ambient air to a QD emitting layer. Moreover, the wet chemistry processing for their formation makes metal oxide layers attractive for low cost and/or large area manufacture of QLEDs.

All solution‐processed white quantum‐dot light‐emitting diodes with three‐unit tandem structure

“…To solve this problem, the ICL should be fabricated by solution method and can survive after solution processing form many times. In addition, solution processing is a promising way to make large area yet low cost displays . For the aforementioned reasons, we investigate the possibility of fabricating all solution‐processed tandem white QLEDs using a new ICL based on ZnMgO/PEDOT:PSS heterojunction.…”

“…[1][2][3][4][5][6][7] With the development of the QD materials and the device structures, the performances of the QLEDs have been rapidly and significantly improved. 8,9 For example, red, green and blue QLEDs with external quantum efficiencies (EQE) of 20.5, 10 21 11 and 12.2%, 2 respectively, have been demonstrated recently. The efficiencies of QLEDs are getting closer to those of organic (O) LEDs, whereas the color saturation of QLEDs is significantly higher than that of OLEDs.…”

“…In addition, solution processing is a promising way to make large area yet low cost displays. 9,[21][22][23] For the aforementioned reasons, we investigate the possibility of fabricating all solution-processed tandem white QLEDs using a new ICL based on ZnMgO/PEDOT:PSS heterojunction. ZnMgO and PEDOT:PSS are the conventional electron and hole injection materials, respectively, which have been widely used in QLEDs because of their high transmittance, high carrier mobility and well matched energy levels with those of the respective adjacent layers.…”

Solution-Processable MoO<italic>x</italic>for Efficient Light-Emitting Diodes Based on Giant Quantum Dots

“…Though these materials are efficient p-type semiconductors, the process is generally not a cost-effective fabrication. Following these ideas, recently solution-processable WO3 NPs, and NiO via sol-gel processes [12][13][14] have also been applied and highly appreciated as potential stable hole injection materials for QLEDs. However, their EL performance is generally far from that of the conducting polymer-based device.…”

Flexible large area organic light emitting diode fabricated by electrohydrodynamics atomization technique

“…The conjugated polymer devices have advantages like easy fabrication, low cost, lightweight, human friendly, sustainable raw materials, very thin, large view angle, and fast response [4,5]. The solution-based polymers make the fabrication process easier as compared to the inorganic conventional LEDs [6]. The LED lamps today achieve the most efficient lighting but OLEDs are even outperforming LEDs in performance [7].…”