共軛高分子薄膜的分子疊積對載子遷移率的影響

在本研究中MEH-PPV 以氯苯當作溶劑並以旋轉塗佈的方法製成薄膜與發光二極體元件，探討MEH-PPV 薄膜的型態和電荷載子傳導特性的相關性，使用到的量測儀器分別有吸收光譜，螢光光譜，時間解析電激發光，雷射光反射和散射的實驗。藉由改變不同的轉速和熱處理的方法來控制高分子薄膜的分子型態。結果顯示了使用旋轉塗佈方法製成的薄膜會在靠近基板表面的地方形成一層很薄的高電子密度層(分子排列所導致的), 這個高電子密度層是造成以旋轉塗佈方式製成的薄膜其載子遷移率要比以滴式塗佈的方式來的低的主要原因，而越薄的薄膜(使用較大轉速)其載子遷移率越低這是因為使用較高的轉速會產生較高的離心力導致分子高度排列而形成密度更高的電子層。另一個使用熱處理方法的結果為高分子薄膜在經由熱處理過後會從幾乎無序排列的結構變成有規則的薄片狀結構。每個薄板層是由高分子的主鏈所堆疊成的結構，這個結構使得載子能較快速的跳躍通過高分子層而增進其載子遷移率。

關鍵字

時間解析電激發光；載子遷移率；旋轉塗佈法；型態；光學特性； X光反射； X光散射。

並列摘要

The correlation between morphology and charge carrier transport for films spin-cast from MEH-PPV/chlorobenzene solution are investigated by means of UV-vis absorption spectrometer, photoluminescence spectrometer, transient electroluminescence, X-ray reflectivity and grazing incident wide angle X-ray scattering techniques. Film morphology is controlled by using various spin speeds as well as by thermal heat treatment. The result shows there is one thin layer of high electron density (due to the molecular packing) formed near the substrate for films prepared by using spin-cast method. This high electron density layer in spin-cast films is the key factor reducing the carrier mobility compared with drop cast films (reported in previous works). The thinner film (spun at higher spin speed) reveals a lower mobility due to the higher centrifugal force leading to higher molecular packing. With subsequent thermal annealing, the film morphology is changed from “nearly” amorphous to ordered lamellar structure. Each lamellar board is constructed by the stacked MEH-PPV backbones, thus carriers can move quickly within the board by hopping across the neighboring chains resulting in a higher mobility compared with the as spin-cast film.

並列關鍵字

Transient Electroluminescence (TrEL) ； Mobility ； Spin-cast method ； Morphology ； Optical properties ； X-ray reflectivity ； X-ray scattering.

參考文獻

1. Frommer, J. E.; Chance, R. R. In Encyclopedia of Polymer Science and Engineering, Vol. 5; Wiley: New York, 1986.

2. Ito, T.; Shirakawa, H.; Ikeda, S. J. Polym. Sci. Chem. Ed. 12, 11, 1974.

4. Wilbourn, K.; Murray, R. W. J. Phys. Chem. 92, 3642, 1998.

6. Forrest S.; Burrows P.; and Thompson M. IEEE Spectrum 37:29, 2000.

7. Dimitrakopoulos CD and Malenfant PRL, Adv Mater 14:99, 2002.

國際替代計量

共軛高分子薄膜的分子疊積對載子遷移率的影響

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