具週期性表面起伏結構之有機發光二極體元件

Investigation of Corrugation Organic Light Emitting Diodes

翁睿甜(Ruei-Tian Wong)

指導教授 ： 吳忠幟

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202103199

摘要

本篇論文首先簡介有機發光二極體（Organic light emitting diode, OLED）的歷史與原理，並且介紹光場立體顯示技術的幾種常見作法與優缺點，接著提出一個奠基於有機發光二極體之上的光場顯示架構，其中包含兩大部分，分別為高指向性光源與光線偏折結構。本研究主要聚焦在第一部分高指向性光源，介紹以週期性結構實現高指向性有機發光二極體元件的原理，即設計OLED結構將能量集中於某一高波向量（k）值模態，接著以週期性結構的基板來將高波向量（high-k）模態轉換到低波向量（low-k）模態，並透過初步模擬驗證其可行性。接下來以三種不同方法實作週期性結構基板，包含加熱融化奈米小球、在圖案化藍寶石基板上沉積SiO2以及在圖案化藍寶石基板上旋轉塗佈透明光阻，以光學顯微鏡、掃描式電子顯微鏡與原子力顯微鏡觀察結果，並比較它們各自的優缺點。接著以時域有限差分法（Finite-difference time-domain, FDTD）模擬探討在圖案化藍寶石基板與ITO電極之間插入SiO2層的厚度與電子傳輸層（Electron-transport layer, ETL）厚度對指向性的影響，並且實作完整的OLED元件，透過量測其發光場型與變角度頻譜，並與平面元件做比較，成功得到場型更為集中的元件，初步驗證了週期性結構的基板能夠將高波向量模態轉換到低波向量模態，但其仍與模擬結果以及能實際應用於光場顯示的要求有些差距，因此也探討了造成這些差距的可能原因。最後對於未來能夠進一步改進和發展的方向提出討論。

關鍵字

高指向性有機發光元件 ； 光場顯示 ； 奈米結構 ； 週期性結構基板 ； 角度分布特性

並列摘要

This thesis first introduced the history and principles of organic light emitting diodes as well as light-field displays. We then proposed a configuration for OLED light-field displays which consists of two main parts, including high directivity OLED light source and beam deflection structures. This research focused on the first part, the high directivity OLED light source. Firstly, we introduced the theory of achieving high directivity OLED light source with periodic nano-corrugation structures. Then we fabricated nano-structured and corrugated substrates with three different methods, including melting self-assembled polystyrene nanospheres, sputtering SiO2 on patterned sapphire substrates (PSS) and spin-coating transparent photoresist on patterned sapphire substrates. By comparing the pros and cons of these three methods with optical microscopy, scanning electron microscopy and atomic force microscopy, we decided to fabricate complete OLED device on the patterned sapphire substrate overcoated with the transparent photoresist. With the aid of finite-difference time-domain (FDTD) simulation, we investigated the influence of the thickness of SiO2 interlayer between PSS and ITO electrode as well as the thickness of electron-transport layer (ETL). We then fabricated complete OLED devices based on the simulation results. By measuring the emission pattern and angle-resolved EL spectra, we verified that periodically nano-structured substrates could yield OLEDs with enhanced directionality. Compared to planar devices, PSS devices showed better directivity. However, when considering practical light-field displays, the results were not satisfactory enough. Therefore, we discussed possible reasons that might cause non-ideal effects. Lastly, we proposed some future works that may further improve the work.

並列關鍵字

High directivity OLEDs ； Light-field display ； Nano-structures ； Periodic corrugated structures ； Angular characteristics

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