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Open AccessArticle

Ultra-Violet Electroluminescence of ZnO Nanorods/MEH-PPV Heterojunctions by Optimizing Their Thickness and Using AZO as a Transparent Conductive Electrode

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Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
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Physics and Engineering Mathematics Department, Faculty of Electronic Engineering, Menoufia University, Menouf 32952, Egypt
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Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044, China
*
Authors to whom correspondence should be addressed.
Materials 2019, 12(18), 2976; https://doi.org/10.3390/ma12182976
Received: 17 July 2019 / Revised: 28 August 2019 / Accepted: 10 September 2019 / Published: 14 September 2019
(This article belongs to the Section Optics and Photonics)
In this paper, a series of ITO/ZnO/ZnO nanorods/MEH-PPV/Al were prepared with different thicknesses of MEH-PPV that were changed from 15, 10 to 7 nm. The electric field in the devices was analyzed. An increase in the electric field on ZnO made hole injection easy and the electrons tunnel fast through thinner MEH-PPV to ZnO. This made the carriers prefer to recombine inside the ZnO layer, and the emission of ZnO was predominant under direct current (DC) bias. Furthermore, another device was fabricated with the structure of AZO (Al-doped ZnO)/ZnO/ZnO nanorods/MEH-PPV/Al. Ultra-violet (UV) electroluminescence (EL) at 387 nm from ZnO band edge emission was realized under DC bias. The turn-on voltage of the devices having AZO as the electrode is lower than that of ITO, and the EL power is enhanced. This work also studies the effect of inserting LiF underneath the Al electrode and above the layer of MEH-PPV. The LiF film inserted caused an obvious decrease in turn-on voltage of the devices and a pronounced increase in the EL power. The mechanism of electroluminescence enhancement is also discussed. View Full-Text
Keywords: electroluminescence; ZnO nanorods; heterojunctions electroluminescence; ZnO nanorods; heterojunctions
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MDPI and ACS Style

Wageh, S.; Zhao, S.-L.; Xie, X.-Y.; Gao, S.; Al-Ghamdi, A. Ultra-Violet Electroluminescence of ZnO Nanorods/MEH-PPV Heterojunctions by Optimizing Their Thickness and Using AZO as a Transparent Conductive Electrode. Materials 2019, 12, 2976.

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