複習幾種電荷注入於共軛高分子薄膜傳輸結果。空間電荷限制穿透電流(SCTC)與空間電荷限制傳輸電流(SCLC)等模型，被使用於解釋電荷於共軛高分子薄膜之注入與傳輸機制。基於區域近似分析觀念，電子電流密度從金屬穿透於高分子薄膜之最低未佔據分子軌域將受到空間電荷效應。此空間電荷隨著離電極端距離增加而遞減。假若空間電荷僅佔據於穿透距離與聚集電極端間之限制區範圍內，則電流大小發現將與偏壓的冪定律參數無關。然而，假若空間電荷佔據於穿透距離與聚集電極端間之整體範圍，則電流大小隨偏壓指數變化到較低偏壓情況，且在較高偏壓條件為Child’s定律(區域I)，在中等偏壓下為陷阱填滿限制電流(區域II)，在較低偏壓下顯示為歐姆定律操作(區域III)。當電荷注入位能障較低且高分子層較厚情況下，則空間電荷限制穿透電流傳輸將與空間電荷限制傳輸理論顯現出相同的結果。
在不同的偏壓下，電荷傳輸機制可藉由背景濃度、陷阱狀態密度與空間電荷等參數效應來分析與研究。結果顯示傳輸電流將隨陷阱狀態密度與特性溫度參數增加而遞減。
在此研究中，區域近似被應用於推算電荷於有機薄膜內部之注入與電流傳輸機制。空間電荷限制穿透電流與空間電荷限制傳輸機制等理論模型與實驗值比較，顯示理論與實驗數據有較佳的關係。我們的模型提出一新的方法簡單推算且討論電荷於有機發光二極體傳輸的傳輸現象。

Several results were reviewed on the charge injection into thin conjugated polymer films. The space charge limited tunneling current (SCTC) and space-charge limited current (SCLC) models were used to explain the charge injection and transport in conjugated polymer films such as those used in organic light emitting diodes. On the basis of regional approximation, the effect of the space charge on the current density of electrons tunneling from metal electrodes to the lowest unoccupied molecular orbital of a polymer film is calculated. The space charge is considered to decrease with increasing distance of the injecting electrode. If the space charge occupies only a limited region between the tunneling (short) distance and the collecting electrode, the current (I) is found to be independent on a power law of the applied voltage (V). However, if the space charge occupies all the region between the tunneling distance and the collecting electrode, I is found to vary exponentially on V for lower V values, and that follow approximately the law of Child at high V in region I, the law of Trap filled limited current at middle voltage in region II and the region III show Ohm’s law at lower voltage. The space charge limited tunneling current (SCTC) theory gives the same results of the space charge limited conduction theory when the energy barrier for charge carrier injection is small or when the polymer layer is thick.
Under various bias voltages, the charge transport mechanism was analyzed to investigate the effects on the thin conjugated polymer films induced by the parameters such as background concentration, trap-state density and space charge etc... The results show the transport current decrease with increasing the trap-state density and also increase the characteristic temperature parameters.
In this study, the regional approximation is applied to calculate the charge injection and current transport mechanism in the organic thin film. The SCTC and SCLC models are compared to the experimental data. It shows that there is a good agreement between theory and experiment, concerning both current magnitude and current versus voltage dependence. It is very important that our model gave a new way to simplify the calculation and to discuss the charge transport of organic light emitting diode.

目 錄
中文摘要 i
英文摘要 ii
目錄 iv
附表目錄 vi
附圖目錄 vii
第壹章 緒論…………………………………………….. 1
1-1 前言…………………………………………… 1
1-2 OLEDs歷史簡介………..……………………. 2
1-3 有機半導體特性….……………….………….. 4
1-4 有機電激發光元件之發光原理…….………... 5
1-5 元件結構形式……………….…………..……. 7
1-6全彩化製作技術………………………………. 9
1-7論文目的與章節架構…………………………. 10
第貳章 文獻回顧……………………………………… 11
2-1介面注入限制傳輸理論………………………. 11
2-1-1介面接觸物理現象……………………….. 11
2-1-1-1能階調準(alignment)機制…………… 12
2-1-1-2有機層能帶彎曲機制………………... 12
2-1-1-3載子注入能障機制…………………... 13
2-1-2電荷注入傳輸物理觀念………………….. 15
2-1-2-1 庫侖吸引力(蕭特基效應)…………... 15
2-1-2-2 熱離子放射理論………………… 16
2-1-2-3 熱離子放射擴散理論………….. 17
2-1-2-4 Fowler-Nordheim穿透理論…… 19
2-2空間電荷限制傳輸理論………………………. 22
2-2-1載子遷移率模型………………………….. 22
2-2-2空間電荷限制傳輸之物理現象………….. 22
2-2-2-1 陷阱狀態分布型式…………………….. 24
2-3 復合機制…………………….…………………. 27
2-4雙載子傳輸模型…………………….………….. 28
第參章 模型建構…………………….………………... 31
3-1電荷注入模型描述……………………………. 31
3-2模型一―有機半導體特性傳輸限制…………. 31
3-2-1推導參數定義…………………………….. 32
3-2-1-1各區間操作之定義…………………. 32
3-2-1-2點空間參數之定義…………………. 34
3-2-1-3邊界條件之定義……………………. 35
3-2-1-4模型一推導程序……………………. 36
3-3模型二―電荷注入限制傳輸………………….. 39
3-3-1介面限制傳輸模型………………………. 40
3-3-2空間電荷限制穿透傳輸模型……... 41
3-3-2-1推導參數定義………………………. 42
3-3-2-1-1各區間操作之定義…………….. 42
3-3-2-1-2邊界條件之定義……………….. 43
3-3-2-1-3模型二推導程序……………….. 44
第肆章 結果與討論………………………………………... 48
第伍章 結論…………………………………………….. 51
參考文獻………………………………………………….. 53

附表目錄
表2-1 不同型態半導體材料與金屬接觸之理想介面機制……………………………………… 56
表2-2 ITO/MEH-PPV/不同陰極材料單層結構之外部量子效率…………………………… 56
表2-3 以共軛高分子材料之不同元件結構的傳輸理論機制………………………………… 57
表5-1 高分子與小分子電激發光顯示器之差異…..… 58

附圖目錄
圖1-1 有機電激發光元件之能量吸收與輻射機制程序……………....………….…………....….……. 59
圖1-2 有機電激發光元件的發光原理……….....…..… 59
圖1-3a ITO/EML/Cathode結構..……………..………… 60
圖1-3b ITO/HTL/EML/Cathode結構…..………………. 60
圖1-3c ITO/HTL/EML/ETL/Cathode結構……….…….. 61
圖1-3d ITO/HIL/HTL/EML/ETL/EIL/Cathode結構.…... 61
圖2-1a 理想金屬/半導體接觸之介面能障機制……..… 62
圖2-1b 金屬/半導體介面存在表面電荷密度之位能障機制..……………..………..…………...…..…… 62
圖2-2a 在無限空間距離之金屬與有機固態的電子結構..……………..………..………………..…… 63
圖2-2b 金屬與薄有機固體層之接觸型態。當兩固體材料接觸在一起時，將存在於一金屬/有機層間介面能障。實際電位能井如虛線所示…………… 63
圖2-3 偶極層內部存在一陡峭電子位能障………..… 64
圖2-4a 介面無偶極層存在，且介面電位障為固定值… 64
圖2-4b 介面存在一偶極層，而產生介面電位障彎曲現象……………………………………………..… 65
圖2-5a 介面無偶極效應(Δ＝0)之能帶彎曲現象…..… 65
圖2-5b 介面發生偶極效應(Δ≠0)之能帶彎曲現象…. 66
圖2-6 介面注入機制型態，基本上可以分成以下四種傳輸過程………………………..…… 66
圖2-7 蕭特基效應造成位能障隨距離遞增而遞減….. 67
圖2-8 介面注入電流密度與電場函數之特性曲線….. 67

圖2-9 Fowler-Nordheim理論，針對Al/PPV/不同金屬材料之電子注入單層結構接觸位能障的效率曲線……………………………………………... 68
圖2-10 不同陽極材料/MEH-PPV/Au單層結構之電流電壓特性曲線…………………………………... 69
圖2-11 冪定律l對電流電壓特性曲線關係…………… 69
圖2-12 ITO/TPD/Alq3/Mg:Ag雙層異質結構，指數陷阱狀態分布於Alq3能帶隙的電子準費米能階以上之示意…………………………………….. 70
圖2-13a 有機薄膜厚度變化之電流電壓特性曲線…….. 70
圖2-13b 陷阱狀態能量分布隨著溫度提高而遞增，反之電流電壓特性曲線斜率降低…………………... 71
圖2-14 電洞陷阱濃度hp(E)與被陷捕電洞濃度hp(E)•[1-f(Et)]對能量關係之分布情況……………….. 71
圖2-15 單層有激發光元件結構之雙載子電荷注入傳輸示意圖……………………………………...… 72
圖3-1 有機半導體限制傳輸模型示意圖…………..… 72
圖3-2 ITO/PPV/陰極金屬材料(Al, Ca)蕭特基二極體元件能帶結構示意圖………………………...… 73
圖3-3 空間電荷限制穿透電流機制之載子濃度分布示意圖………………………………………….. 73
圖4-1 推算不同背景摻雜濃度大小之電流電壓特性關係曲線……………………………………...… 74
圖4-2 背景濃度對點空間電流電壓特性關係曲線….. 74
圖4-3 指數陷阱狀態密度對點空間電流電壓特性關係曲線………………………………………...… 75
圖4-4a 在不同偏壓條件下，其注入載子濃度與陷阱狀態密度於有機薄膜內部之分布情形………...… 75
圖4-4b 一般有機半導體受到材料本身特性影響之電流電壓特性曲線……………………………...… 76

圖4-5 不同金屬與Alq3小分子有機材料之蕭特基位能障………………………………………...….. 76
圖4-6 蕭特基二極體Au/PPV/Al與ITO/PPV/Al之單層結構的電流電壓特性曲線……………….….. 77
圖4-7 ITO/PPV/Al, ZnO:Al/PPV/Al與Au/PPV/Al之電流電壓特性曲線……………………………... 77
圖4-8 空間電荷限制穿透電流密度之操作特性曲線 78
圖4-9 空間電荷限制穿透傳輸之電流電壓關係對位能障特性曲線圖………………………….…….. 78
圖4-10 空間電荷限制穿透傳輸之電流電壓關係對有機層厚度特性曲線………………………….….. 79

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