有機發光二極體中載子的傳輸機制研究

The investigation of carrier injection and transport mechanisms in organic light-emitting diodes

劉家偉(Chia-Wei Liu)

指導教授 ： 吳志毅

國立臺灣大學/電機資訊學院/光電工程學研究所/博士(2018年)

https://doi.org/10.6342/NTU201800897

摘要

本論文是關於有機發光二極體的研究，分成四個部分，主要是有關於電洞注入層與電子傳輸層方面。首先是利用自組裝氧化鉬作為電洞注入層的研究，我們發現這種自組裝的方法比起傳統的熱蒸鍍更能有效提升有機發光二極體元件的效率。第二部分是將氧化鉬鑲嵌在硫化鉬的奈米溶液利用旋轉塗佈在陽極基板上做為電洞注入層，我們發現此種氧化鉬硫化鉬的合成材料能有效提高原本功函數不高的硫化鉬且能同時保持硫化鉬的導電性。第三部分則是研究不同電子傳輸層對於磷光發光元件性能的影響，我們發現電子傳輸層對於效率和壽命的影響是成反比關係，但是如果能進一步的使用雙層電子傳輸層結構的話則可以選擇適合的電子傳輸層搭配以達到效率和壽命取捨的最佳化。最後第四部份則是分析不同電洞傳輸層的能階位置對元件壽命的影響，我們發現使用具有深層價帶能帶結構的電子傳輸層能有效的提高元件壽命。我們推測其原因在於因其導帶十分接近元件的費米能階進而產生了不同的傳輸機制使得電荷能避免受到陽極與有機材料間缺陷的影響。

關鍵字

有機發光二極體 ； 氧化鉬 ； 硫化鉬 ； 電洞注入層 ； 電子傳輸層 ； 元件壽命

並列摘要

This dissertation is to investigate the carrier injection and transport mechanisms in organic light-emitting diodes, mainly associating with the hole injection layer and electron transport layer. There are four sections in this dissertation. First, we demonstrate the use of self-assembly to fabricate solution-processed molybdenum oxide films by simply casting a metal oxide solution onto an indium tin oxide substrate. The devices with self-assembled hole injection layers exhibited nearly double the efficiency of one made with commonly used evaporated molybdenum oxide hole injection layers. Second, we demonstrate the use of solution-processed molybdenum trioxide nanoparticle-decorated molybdenum disulfide (MoS2) nanosheets (MoS2/MoO3) as hole injection layer in organic lighting diodes. The device performance is shown to be significantly improved by the introduction of such MoS2/MoO3 hole injection layer without any post-ultraviolet-ozone treatment, and is shown to better the performance of devices fabricated using conventional. Third, The influence of the electron-transport layer on an Ir(ppy)3-based phosphorescent light-emitting diode was investigated. We found that although devices with pyridine-containing ETLs, bis-1,2-(3,5-di-3-pyridyl-phenyl)benzene (B3PyPb) and 1,3,5-tri(m-pyrid-3-ylphenyl)benzene (TmPyPb), achieved very high efficiencies, their lifetimes were worse than other commonly used ETLs. However, the device lifetime can be increased by utilizing a high-stability electron-blocking layer to avoid triplet-polaron annihilation by separating the excitons in the emitting layer and the polarons in the electron transport layer. Fourth, we will discuss a series of standard organic light-emitting diode with various hole-injection layers in order to identify the origin of luminance degradation and the role played by hole injection layers in device lifetime. Band alignment results in the formation of a well-formed charge transfer interface capable of preventing the accumulation of charge at the indium tin oxide/hole transport layer interface. Keywords: Light-emitting diodes, MoO3, MoS2, Hole injection layer, Electron transport layer, Device lifetime.

並列關鍵字

Light-emitting diodes ； MoO3 ； MoS2 ； Hole injection layer ； Electron transport layer ； Device lifetime

參考文獻

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