透過同步輻射光研究有機光電元件電極之電子結構與介面分析

Investigation of electronic structures and interfacial chemistries of electrodes in organic optoelectric devices via synchrotron radiation induced photoemission spectroscopy

廖國凱(Guo-Kai Liao)

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/碩士(2014年)

https://doi.org/10.6342/NTU.2014.01525

摘要

本篇論文主要研究如何改善有機光電元件的電極端，以便於提升載子注入效率以及導電率和元件表現，並透過同步輻射光所得到的光電子能譜來研究其物理和化學機制
　　首先我們在有機發光二極體的純電洞元件上使用三氧化鉬當作電洞注入層。而在本篇論文中我們發現，較薄厚度的三氧化鉬其鉬原子會產生明顯的還原反應，因而在三氧化鉬的能隙中產生能隙能階提供電洞傳輸路徑，進而提升電洞注入的效果。
　　另一方面在有機太陽能電池元件上，我們使用石墨烯當作其電極，而在本篇論文中我們發現，用Polymer-free轉移法除了可以獲得高品質的石墨烯以及大大降低了污染物殘留的問題外，使用Polymer-free轉移法的石墨烯也擁有較高的導電率，綜合以上兩點都比傳統的轉移法來的出色，也更適合拿來當作電極使用。此外為了解決電極與載子傳輸層間載子注入能障的問題，我們嘗試將石墨烯參雜不一樣的物質，藉此改變其功函數，讓電極的費米能階盡可能地與載子傳輸層的HOMO或LUMO匹配，如此不僅提升了有機太陽能電池的各項參數，且隨著參雜物的不同也會增加石墨烯的導電率，使石墨烯在電極上的應用開拓了更多的優勢與可能性。

關鍵字

光電子能譜 ； 有機發光二極體 ； 石墨烯 ； 三氧化鉬 ； 同步輻射

並列摘要

In this thesis, we study the methods to improve the effectiveness of electrodes in organic optoelectronic devices, in particular to enhance the efficiency of carrier injection, conductivity and hence the devices performance. In addition, high-resolution synchrotron radiation induced photoelectron spectroscopy was used to study the chemical and physical properties at the device interfaces.
　　First, we investigate molybdenum trioxide (MoO3) as hole injection layers in hole only devices. The reductions of Mo atoms are more obvious in the devices with thinner MoO3 layers, with more gap states to increase the hole injection path and to enhance the efficiency of injection.
　　On the other topic, we use graphene as electrodes in organic solar cell devices. We demonstrated the polymer-free transfer method that can transfer large area CVD-graphene to any substrate to reduce surface tension and residual contaminant. The polymer-free transferred graphene films also show good quality and high electrical conductance that make them suitable for conductive electrodes. Furthermore, in order to resolve the carrier injection barrier problem, we use doping process to change the work function of the graphene. It decreases misalignment between the Fermi level of electrodes and the HOMO and LUMO level of carrier transport layers. As a result, it not only enhances the device performance but also increases the conductivity of graphene, which provide more advantages for graphene application in the future.

並列關鍵字

OLED ； photoemission spectroscopy ； graphene ； Molybdenum trioxide ； synchrotron radiation

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