以carbazole為供體，benzimidazole為受體，合成了一系列不同π電子共軛的雙極分子。主體材料的最大吸收波長從305至342 nm，放光光譜的波峰範圍從347至443 nm。由理論計算得到主體分子的carbazole和benzene之間的兩面角最小為35.4°，最大為89.6°。我們成功的利用增加立體障礙的方式獲得大的扭轉角來減少分子內的共振機率，藉此提高主體分子的LUMO能階。在獲得高的LUMO能階的情況下這些材料有高的潛力作為OLED元件中的主體。在元件的測試結果中，以p-CbzBiz用作於綠色磷光發射體Ir(ppy)2(acac)的主體時，OLED元件的最大外部量子效率達到21.8%。此外，當o-CbzBiz用於綠色螢光發光體4CzIPN的主體時，OLED元件的最大外部量子效率可以達到16.7%。因此，基於carbazole/benzimidazole為主所設計的分子有潛力做為磷光或TADF OLED發光體的主體材料。

A series of bipolar molecules, which are different kinds of π-bridge were synthesized using carbazole as the donor and the benzimidazole as the acceptor. These host meterials exhibited a maximum UV absorption band ranging from the 305 to 342 nm, and a maximum emission band ranging from 347 to 443 nm. Density functional theory calculations showed that the twist angle between the donor and acceptor moiety is of these molecules were from 35.4° to 89.6°. Such twisted structure hampered the π-electron conjugation within the molecule and resulted in high-lying LUMO levels, which make them potential hosts for the emitters in OLED devices. Our results showed that a maximum external quantum efficiency (EQE) of OLED reached 21.8% when p-CbzBiz was applied as the host of a green phosphorescent emitter Ir(ppy)2(acac). In addition, a maximum EQE of OLED reached 16.7% when o-CbzBiz with the host of a green TADF emitter 4CzIPN was achieved. Therefore, the carbazole/benzimidazole-based molecules are potential to be universal hosts in OLEDs applications.

目錄
圖目錄	                        viii
第一章 、緒論	                1
1-1 前言	                2
1-2 發光材料之放光機制	        2
1-2-1 螢光	                2
1-2-2 磷光	                5
1-2-3 熱活化延遲螢光	        6
1-3 多層OLED結構	                6
1-3-1 能階示意圖	                6
1-3-2 陽極材料	                7
1-3-3 電洞注入材料	        7
1-3-4 電洞傳輸材料	        8
1-3-5電子傳輸材料	        9
1-3-6 陰極材料	                9
1-4 主客體發光系統	        10
1-4-2 摻雜螢光材料之元件的能量轉移	11
1-4-3摻雜磷光材料之元件的能量轉移	12
1-4 有機發光二極體元件相關係數	13
1-4-1的元件發光效率	        13
第二章 、結果與討論	        16
2-1 研究背景	                17
2-2分子結構設計	                19
2-4 光化學性質	                24
2-5 熱穩定性性質	                31
2-6電化學性質	                33
2-7理論計算	                36
2-8主體分子的電子電洞傳輸速率	38
2-9 磷光發光體元件效率	        39
2-10 熱活化延遲螢光發光體元件效率	42
2-11結論	                44
實驗儀器	                        45
實驗藥品	                        47
實驗合成步驟和相關光譜數據	50
9-(2-bromophenyl)-9H-carbazole (a)	50
9-(3-bromophenyl)-9H-carbazole (b)	51
9-(thiophen-2-yl)-9H-carbazole (e)	52
9-(thiophen-3-yl)-9H-carbazole (f)	53
9-(4-bromo-2,5-dimethylphenyl)-9H-carbazole (g)	54
4-bromo-2,5-dimethylbenzaldehyde (h)	55
2-(4-bromo-2,5-dimethylphenyl)-1-phenyl-1H-benzo[d]imidazole(i)	56
9-(4-bromo-3-methylphenyl)-9H-carbazole (j)	57
2-(4-bromo-3-methylphenyl)-1-phenyl-1H-benzo[d]imidazole (k)	58
9-(4'-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1'-biphenyl]-2-yl)-9H-carbazole (o-CbzBiz)	59
9-(4'-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1'-biphenyl]-3-yl)-9H-carbazole (m-CbzBiz)	61
9-(4'-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1'-biphenyl]-4-yl)-9H-carbazole (p-CbzBiz)	63
9-(5-(4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)thiophen-2-yl)-9H-carbazole (2-CbzTBiz)	65
9-(5-(4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)thiophen-3-yl)-9H-carbazole (3-CbzTBiz)	67
9-(2,2',5,5'-tetramethyl-4'-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1'-biphenyl]-4-yl)-9H-carbazole(tm-p-CbzBiz)	69
9-(2,2'-dimethyl-4'-(1-phenyl-1H-benzo[d]imidazol-2-yl)-[1,1'-biphenyl]-4-yl)-9H-carbazole(dm-p-CbzBiz)	71
附圖	76

 
圖目錄
圖1-1、Jablonski diagram。	3
圖1-2、多層式有機發光二極體元件結構示意圖	   7
圖1-3、(a) C. W. Tang 等人所提出之低壓雙層OLED 元件; (b) 主-客摻雜系統之電致發光光譜(1) 未摻雜Alq3,  (2) C540/Alq3, and (3) DCM1/Alq3.	10
圖1-4、螢光摻雜(fluorescent dopant)元件的能量傳遞圖	12
圖1-5、磷光摻雜(phosphorescent dopant)元件的能量傳遞圖	13
圖2-1、主體分子在二氯甲烷中的UV吸收光譜。	25
圖2-2、主體分子在二氯甲烷中的螢光放光光譜和磷光放光光譜。	26
圖2-3、o-CbzBiz、m-CbzBiz和p-CbzBiz在薄膜狀態的螢光和磷光放光光譜。	28
圖2-4、o-CbzBiz、m-CbzBiz和p-CbzBiz在甲苯中的吸收和放光光譜。	29
圖2-5、o-CbzBiz、m-CbzBiz和p-CbzBiz在二氯甲烷、四氫呋喃和甲苯中的螢光放光光譜。	30
圖2-6、o-CbzBiz、m-CbzBiz、p-CbzBiz、tm-p-CbzBiz和dm-p-CbzBiz的熱重分析圖。	31
圖2-7、o-CbzBiz、m-CbzBiz和p-CbzBiz的玻璃轉移溫度圖。	32
圖2-8、主體分子的循環伏安圖。	34
圖2-9、主體分子的HOMO-LUMO電子分布和環與環之間的二面角角度。	37
圖2-10、(a) Current density-voltage curves of hole and electron only devices; (b) Hole mobilities versus E1/2 for p-CbzBiz.	38
圖2-11、PhOLED的元件能階圖。	40
圖2-12、(a) 電致發光光譜；(b) 電流和功率效率的關係；(c) PhOLED的外部量子效率(EQE)與亮度的關係；(d) 電流密度-電壓-亮度(J-V-L)圖。	40
圖2-13、TADF OLED的元件能階圖。	42
圖2-14、(a)電致發光光譜；(b)電流和功率效率的關係；(c)TADF OLED的外部量子效率(EQE)與亮度的關係；(d)電流密度-電壓-亮度(J-V-L)圖。	43

 
表目錄
表2-1、主體分子的光物理性質	27
表2-2、主體分子在薄膜的光物理性質	28
表2-3、主體分子在甲苯中的光物理性質	29
表2-4、o-CbzBiz、m-CbzBiz、p-CbzBiz、tm-p-CbzBiz和dm-p-CbzBiz的熔點、玻璃轉化溫度和熱裂解溫度。	32
表2-5、主體分子的電化學性質。	34
表2-6、主體分子的電化學性質。	35
表2-7、主體分子的PhOLED的元件性能。	41
表2-8、主體分子的TADF OLED的元件性能。	43

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