Impedance Spectroscopy of Organic Light-Emitting Devices
Date Issued
2014
Date
2014
Author(s)
Lin, Hui-Ting
Abstract
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.
Subjects
有機發光元件
阻抗頻譜
等效電路
導電摻雜
時間常數
Type
thesis
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