有機發光元件之阻抗分析技術

Abstract

近年來，有機發光元件已經快速發展成一具有潛力的平面顯示技術，為了滿足高效率、低操作電壓、長壽命的元件特性要求，必須設法了解元件材料、介面與整體特性。然而，這些有機發光元件中重要的現象與機制一般並不易從最典型的 I-V-L 量測中獲得明確的相關資訊，因此希望能藉由對於材料本身及介面特性相當靈敏的阻抗分析技術之輔助，深入研究有機發光元件，改善並提升元件特性。 在本論文的第一部份中，我們針對單層有機元件之阻抗頻譜做深入探討，接著利用Fluxim有機元件模擬程式，模擬單層有機電洞材料(HI010)元件內部載子濃度隨位置分布情形，並配合電路模型，推測造成元件阻抗頻譜在等效電路中分層的原因之一為電性不同，即不同的時間常數。 在本論文的第二部份中，我們針對單載子有機電洞材料層元件之阻抗頻譜做深入探討。我們分別使用「電洞注入材料(HI008)/電洞注入材料(HI010)」與「電洞注入材料(HI008)/電洞注入材料(HI010)/電洞傳輸材料(HT006)」製作雙層及三層電洞材料元件，改變兩種結構中某一層的材料厚度，探討不同厚度下，元件在阻抗頻譜上的變化。 在本論文的第三部份中，我們針對單載子有機電子材料層元件之阻抗頻譜做深入探討。我們分別使用「單層n型摻雜電子傳輸材料(n-ET011)」與「n型摻雜電子傳輸材料(n-ET011)/電子傳輸材料(ET010)」製作單層及雙層電子材料元件，並對n-ET011和ET010之材料厚度對於阻抗頻譜的影響做一探討，依序改變兩種結構中某一層的材料厚度比較其阻抗頻譜差異。

Organic light-emitting devices (OLEDs) have been demonstrated as a potential display technology. In order to achieve high efficiency, low operating voltage and long operating lifetime, we should understand the characteristics of the materials and interfaces. However, typical I-V-L characteristics cannot reveal these important mechanisms of OLEDs. Impedance spectroscopy (IS) is a powerful method for characterizing many of the electrical properties of materials and their interfaces. With the aid of impedance spectroscopy, we can obtain more insights about the operation of OLEDs. In the first part of the thesis, we investigated impedance spectroscopy of organic single-layer devices. Then, we adopted Fluxim simulation tool to obtain the distance-dependent carrier concentrations in the single-layer device (HI010). Besides, we constructed the equivalent circuits of the devices to demonstrate that one possible reason of different regions occurring in equivalent circuits may be associated with different electrical properties, that is, different time constants. In the second part of the thesis, we adopted impedance spectroscopy to measure hole-only devices. We fabricated two different device structures – “hole-injection material (HI008)/ hole-injection material (HI010)” and “hole-injection material (HI008)/ hole-injection material (HI010)/hole-transport material (HT006)”. We systematically varied the material thickness of the HI008, HI010 and HT006 to investigate their effects on devices. In the third part of the thesis, we performed comparative studies of the impedance spectroscopy of two different structures of electron–only devices– “n-doped electron-transport material (n-ET011) and n-doped electron-transport material (n-ET011)/ electron-transport material (ET010)”. To verify the effects of n-ET011 and ET010 on devices, we systematically varied their material thickness.