臺灣博碩士論文加值系統

本研究是以串聯的概念，將數個發光元件以連接層連接起來，與傳統的元件比較，串聯式元件有較高的發光效率，且在相同的電流密度下，其劣化特性是與傳統的元件相同的，而在元件壽命也是串聯式元件佔優勢。本研究不僅以實驗室所開發的單一發光層白光元件作為基本元件來串聯，也針對連接層對整體元件的影響進行探討。
首先，我們先設計出連接層結構為Alq3：Li (1%)(n型連接層)/MoO3(p型連接層)，並以Alq3為發光層之基本單位進行連接層膜厚的最佳化，整體元件的結構為
ITO/NPB(65 nm)/Alq3(30 nm)/Alq3(30 nm)/Alq3(x nm)：Li (1%)/MoO3(y nm)/NPB(65 nm)/Alq3(30 nm)/Alq3(30 nm)/LiF(0.8 nm)/Al(200 nm)
x=10，20，30，40；y=1，3，5，7，10
比較元件特性曲線圖，我們得到n型連接層Alq3：Li (1%)最佳膜厚為20 nm，p型連接層MoO3最佳膜厚為5 nm；研究裡，我們逐步排除了連接層厚度變化之穿透與吸收會影響整體元件效率的可能性，而推論出連接層的膜厚會影響我們所串聯二個基本元件之間載子傳輸速率之平衡，故不論在n型或者是p型連接層中，都有一個最佳膜厚，讓整個串聯式元件能發揮出最佳的發光特性。
最後我們將本實驗室開發出的單一發光層白光元件，使用1,3,5-Tri(1-pyrenyl)benzene (TPB3)作為主發光體材料，並以4-(dicyanomethylene)-2-tert-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB)作為客發光體材料，元件結構為ITO(130 nm)/NPB(65 nm)/ TPB3(30 nm)：DCJTB(0.05%)/ Alq3(30 nm)/LiF(0.8 nm)/Al(200 nm)
其串聯式元件結構為ITO(130 nm)/NPB(65 nm)/ TPB3(30 nm)：DCJTB(0.05%)/ Alq3(30 nm)/Alq3(20 nm)：Li(1%)/MoO3(5 nm)/
NPB(65 nm)/TPB3(30 nm)：DCJTB(0.05%)/Alq3(30 nm)/
LiF(0.8 nm)/Al(200 nm)
我們得到在相同電流密度下能驅動將近四倍於基本白光元件之亮度(670 cd/m2 for 2360 cd/m2 at 20 mA/cm2)，此特性對於元件壽命有極大助益，最大效率來到9.7 cd/A( at 24 mA/cm2)，但由於元件之驅動電壓過大，在電性與功率效率方面有較大的落差。
於是我們改變n型連接層Alq3：Li (z %)，z=1%，2%，3%之摻雜濃度以期改善電性方面的不足，並以不同濃度之穿透與吸收來探討。我們發現確實改善了驅動電壓的問題(由10 V降至7 V)，但是在元件光性方面卻下降了，同樣的不同摻雜濃度之穿透跟吸收並無太大差異，於是我們推論增加了n型連接層的傳導能力，雖改善了電性劣勢，卻也造成載子傳輸不平衡，以致光性特性下降。但我們還是在摻雜濃度2%的元件中，效率達到8.1 cd/A( at 14V)，相同電流密度下能驅動三倍於基本白光元件之亮度(670 cd/m2 for 1760 cd/m2 at 20 mA/cm2)，在15V的時候最接近白光區域為(0.30，0.37)，當電壓在8V~20V的範圍裡，其CIE座標範圍在(0.35，0.46)~(0.28，0.33) ，其對應之電流密度範圍是0~300 mA/cm2；本研究已初步開發出僅以單一白光發光層作為串聯式元件，此種白光串聯式結構是以往從沒被提出過的，並在效率與低電流密度驅動亮度上有所突破，整體特性展現也達平均以上之水準，且元件在大的操作範圍仍能在白光範圍內，有助於提升OLED元件在市場上的競爭力。

We report that the tandem OLEDs made of two electroluminescent (EL) units connected by the interconnecting layer. If It is compared wih the traditional OLEDs. The tandem OLEDs have higher efficiency and well lifetime. We not only used the single emitting layer WOLEDs as EL unit but also studied the effect of the interconnecting layer for whole device.
First, we designed the interconnecting layer with Alq3：Li (1%) (n-doping layer)/MoO3 (p-doping layer), and we optimized the thickness of the interconnecting layer by using green unit cell (Alq3 for EML),
ITO/NPB(65 nm)/Alq3(30 nm)/Alq3(30 nm)/Alq3(x nm)：Li (1%)/MoO3(y nm)/NPB(65 nm)/Alq3(30 nm)/Alq3(30 nm)/LiF(0.8 nm)/Al(200 nm)
x=10，20，30，40；y=1，3，5，7，10
We found that the best thickness of Alq3：Li (1%) and MoO3 are 20 nm and 5 nm. In our study, we concluded that there are the best thickness to each interconnecting layer, and it keeps the charge balance between two units.
Finally, we used our single emitting layer WOLEDs as unit cell, which used 1,3,5-Tri(1-pyrenyl)benzene (TPB3) as the host, and 4-(dicyanomethylene)-2-tert-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as the guest, unit cell was
ITO(130 nm)/NPB(65 nm)/ TPB3(30 nm)：DCJTB(0.05%)/ Alq3(30 nm)/LiF(8 nm)/Al(200 nm)
Whole device was
ITO(130 nm)/NPB(65 nm)/ TPB3(30 nm)：DCJTB(0.05%)/ Alq3(30 nm)/Alq3(20 nm)：Li(1%)/MoO3(5 nm)/NPB(65 nm)/TPB3(30 nm)：DCJTB(0.05%)/Alq3(30 nm)/
LiF(0.8 nm)/Al(200 nm)
We got almost three times luminance from the tandem one at the same current density (670 cd/m2 for 2360 cd/m2 at 20 mA/cm2) and efficiency as high as 9.7 cd/A ( at 24 mA/cm2). It’s a excellent contribution for device lifetime. But the operation voltage and the power efficiency didn’t reach to our expectancy.
In order to improve the disadvantage, we changed the concentration of n-doping layer Alq3：Li (z %)，z=1%，2%，3%. It was actually improved the turn-on voltage from 10 V to 7 V. But the luminescent characteristics also degenerated. Although we enhanced the charge mobility of the n-doping layer, it also caused the degeneration of luminescent characteristics because of the unbalance of the charge transference.We got the efficiency 8.1 cd/A ( at 14 V) and almost two times luminance from the tandem one at the same current density (670 cd/m2 for 1760 cd/m2 at 20 mA/cm2), most close to the white area of CIE coordinates was (0.30 , 0.37) at 15 V. Its range of CIE coordinates was (0.35 , 0.46)~(0.28 , 0.33) at 8 V~20 V. We have already developed the tandem WOLEDs using single white emitting layer as EL units that have never be reported. It not only maintained the advantages of the tandem structure, but also had excellent stability of luminescent characteristics at wide range operation voltage. We reached our goal to improve the WOLEDs and make it more suitable for commercial applications, especially for the development of light sources.

誌謝........................................................................................I
中文摘要................................................................................II
Abstract.................................................................................V
目錄.......................................................................................VII
圖表目錄................................................................................X
第一章 緒論..................................................................1
1-1有機電激發光元件之簡介及歷史發展.........................1
1-2有機電激發光元件之基本結構......................................4
1-3有機電激發光元件之基本發光原理..............................6
1-4有機電激發光元件材料介紹..........................................9
1-4-1 電洞注入層材料..........................9
1-4-2 電洞傳輸層材料........................10
1-4-3 電子注入層材料........................11
1-4-4 電子傳輸層材料........................11
1-4-5 發光層材料................................11
1-4-6 陽極............................................13
1-4-7 陰極............................................14
1-5有機電激發光元件發光效率之定義和測量方法........15
1-5-1 內、外部量子效率...................15
1-5-2 基本光學特性...........................16
1-6有機電激發光元件的色彩鑑定....................................17
1-6-1 色彩學原理................................17
1-6-2 CIE 1931色座標.......................18
第二章 理論基礎與實驗動機.....................................20
2-1有機電激發光能量轉移機制........................................20
2-1-1 Förster能量轉移機制..............20
2-1-2 Dexter能量轉移機制...............25
2-2 白光有機電激發光元件................................26
2-2-1 多摻雜單發光層白光有機電激發光元件.....26
2-2-2 多重發光層白光有機電激發光元件............26
2-2-3 利用活化雙體與活化錯合物的白光有機電激
發光元件........................................................27
2-3 研究動機........................................................29
第三章 實驗方法與設備............................................32
3-1 實驗架構........................................................32
3-2 實驗材料.........................................................35
3-3 實驗設備.........................................................36
3-3-1 製程設備....................................36
3-3-2 量測設備....................................39
3-4 實驗步驟.........................................................45
3-4-1 ITO基板前處理.........................45
3-4-1-1 ITO基板蝕刻........45
3-4-1-2 ITO基板清潔........46
3-4-2 有機與金屬薄膜製程................47
3-4-3 元件封裝製程............................48
第四章 結果與討論.....................................................49
4-1 基礎元件最佳化厚度之選擇.........................49
4-2 串聯式元件連接層膜厚之最佳化.................55
4-2-1 n型連接層Alq3(x Å)：Li (1%)
之膜厚最佳化...........................58
4-2-2 p型連接層MoO3(y Å)之膜厚最
佳化..........................................63
4-3 串聯式單一發光層白光元件之特性分析....70
4-4 n型連接層Alq3：Li (z%)之濃度探討..........77
第五章 總結.................................................................90
參考文獻..............................................................................93

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