以咔唑/苯並咪唑為主所設計出的雙極分子作為高效率的磷光和熱活化延遲螢光發光體主體材料

Carbazole/Benzimidazole-based Bipolar Molecules as the Hosts for Phosphorescent and Thermally Activated Delayed Fluorescence Emitters for Efficient OLEDs

高振傑(Zhen-Jie Gao)

指導教授 ： 陳志欣

淡江大學/理學院/化學學系碩士班/碩士(2020年)

https://doi.org/10.6846/TKU.2020.00749

摘要

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。

關鍵字

有機發光二極體 ； 主體材料 ； 熱活化延遲螢光

並列摘要

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.

並列關鍵字

Organic light-emitting diode ； host materials ； thermally activated delayed fluorescence

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