Size Tunable ZnO Nanoparticles To Enhance Electron Injection in Solution Processed QLEDs

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• 作者：Jiangyong Pan ; Jing Chen ; Qianqian Huang ; Qasim Khan ; Xiang Liu ; Zhi Tao ; Zichen Zhang ; Wei Lei ; Arokia Nathan
• 刊名：ACS Photonics
• 出版年：2016
• 出版时间：February 17, 2016
• 年：2016
• 卷：3
• 期：2
• 页码：215-222
• 全文大小：795K
• ISSN：2330-4022

文摘

Quantum dot (QD) light-emitting diodes (LEDs) are a promising candidate for high-efficiency, color-saturated displays. This work reports on the size effect of sol–gel synthesized ZnO nanoparticles (NPs) in which sizes of 2.9, 4.0, and 5.5 nm, were used as an electron transfer layer in QLEDs. The size of the NPs was estimated by transmission electron microscopy (TEM) and its effect on QLED performance was investigated by photoluminescence decay lifetime and electron mobility of ZnO NPs. It was found that as the size of the NP decreased from 5.5 to 2.9 nm, the conductivity increased, whereby the electron mobility was enhanced from 7.2 × 10^–4 cm²/V·s to 4.8 × 10^–3 cm²/V·s and electron decay lifetime increased from 5.11 to 6.68 ns. A comparison of NP size effects shows that the best performance is achieved with the 2.9 nm sized ZnO, which yields a turn on voltage of 3.3 V, a maximum current efficiency of 12.5 cd/A, power efficiency of 4.69 lm/W and external quantum efficiencies (EQE) of 4.2%. This is most likely due to the higher electron mobility in the smaller ZnO NPs, which facilitates electron transfer from the NPs to QDs, along with the slow exciton dissociation in the QD layer as a result of more favorable energy level alignment at the interface of smaller ZnO NPs and the adjacent emissive layer.