臺灣博碩士論文加值系統

本論文利用交流電性的導納頻譜(Admittance Spectroscopy)，量測高分子發光二極體(PLED)的電性傳輸。我們使用Poly 9,9-dioctylfluorene-alt- thiophene(PDOFT)，分子量10k，並其分子鏈鍵結不同濃度的奈米金粒子(PDOFT-Au)為元件發光層，經由加入不同重量百分比濃度(0%、7.7%、14.3%、20 %)奈米金粒子，發現最高發光亮度達到達到9600(cd/m2)，比未接金PDOFT 最高亮度1940(cd/m2)高出將近5倍的亮度。發光效率則達到0.51(cd/A)，比未接金PDOFT效率(0.1cd/A)為高了5倍以上。
由於高分子發光二極體材料大都是電洞的遷移率(mobility)遠大於電子的載子遷移率，這樣的傳輸不平衡會造成結合發光效率降低。因此本論文利用導納頻譜可以得知電荷的遷移率，並使用普爾-夫倫克效應(Poole–Frenkel Effect)為基礎，成功得到加入奈米金粒子提昇發光效率的原因之ㄧ，是由於電子移動率的提升，以及電洞移動率的減低。實驗得到未加電場的電子移動率由2.21x10^(-5) (cm2/Vs) 提升至6.67x10^(-3) (cm2/Vs)，並且推測最佳的鍵結金粒子濃度約為10%。

This thesis reports the result of frequency dependent dielectric properties of polymer light emitting diode (PLED) by means of admittance spectroscopy. The Poly 9, 9-dioctylfluorene-alt-thiophene (PDOFT) which molecular weights were 10K were synthesized and bonded with different concentrations of AuNPs (PDOFT-Au) as emitting layer. We used four kinds of gold nanoparticle and each had different weight percentage (0%, 7.7%, 14.3%, 20%). The maximum brightness and the maximum current efficiency of the PLED device, using 7.7 wt% gold nanoparticle, were found to be 9600 (cd/m2) and 0.51 (cd/A) , respectively, exhibiting both 5 times of brightness than that of PLED without gold nanoparticle (0 wt%).

Because most PLED materials have their hole mobilities much faster than electron mobilities, such unbalanced transmission will decrease the brightness and the efficiency. Therefore admittance spectroscopy was investigated in this thesis to obtain charge mobility. Also on the basis of applying Poole-Frenkel Effect we successfully found that one of the causes of improved efficiency was due to the increase of electron mobilities and the decrease of hole mobilities. The finding in the thesis is that the electron mobilities μ0 without applying electric field has elevated from 2.21x10^(-5) (cm2/Vs)to 6.67x10^(-3) (cm2/Vs) and also the best synthesized and bonded gold nanoparticle weight percentage which was 10% was estimated.

第一章 序論……………………………………………………………1
1-1簡介 ………………………………………………………1
第二章 實驗原理………………………………………………………5
2-1 一般有機電激發光流程簡介 ……………………………5
2-2高分子電激發光二極體電荷注入理論……………………7
2-2-1 歐姆電流(Ohmic Current) ……………………… 7
2-2-2 穿隧效應 (Tunneling)……………………………8
2-2-3 蕭特基電流(Schotty current) ……………………9
2-2-4空間限制電荷電流(SCLC)與負電容
(Negative Capacitance)現象……………………10
2-3 普爾-夫倫克爾效應 (Poole - Frenkel Effect)…………12
2-4 導納頻譜 (Admittance Spectroscopy)…………………15
2-5 奈米金粒子簡介 ………………………………………18
第三章 實驗儀器與步驟 ……………………………………………21
3-1 實驗儀器介紹……………………………………………21
3-2 實驗步驟 ………………………………………………23
3-2.1 Pattern ITO玻璃……………………………………24
3-2.2樣品的製備…………………………………………26
3-2.3樣品的光電性質量測………………………………29
第四章 結果與討論…………………………………………………..32
4-1 I-V曲線與亮度隨外加偏壓改變 …………………32
4-2 PDOFT-Au Cp對頻率圖…………………………36
4-3 PDOFT-Au 電納(susceptance) 與 移動率(mobility)
………………………………………………………43
4-3.1 PDOFT 電納圖 ……………………………43
4-3.2 PDOFT 載子移動率(mobility) ……………48
第五章 結論………………………………………………………… 53
參考文獻……………………………………………………………… 55

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