有機發光二極體藍光主發光體與紅光高分子材料之合成與性質研究及其元件上的應用

Abstract

中文摘要 本論文分為兩部分，A部分­藍光主發光體材料之合成與性質研究及其元件上的應用；B部分­含有pyrazine基團之紅光高分子材料之合成與性質研究及其元件上的應用。 在A部分中，我們合成出兩個可以應用於藍色磷光元件的主發光體材料9-(3-(5-(4-tert-Butylphenyl)-2-oxadiazoyl)phenyl)-9-(4-diphenyl aminophenyl)-fluorene (此後為方便書寫，簡稱為TPA-F-OXD) 與9-(3-(5-(4-tert-Butylphenyl)-2-oxadiazoyl)phenyl)-9-(9-phenyl-9H-carbazol-3-yl)fluorene (此後為方便書寫，簡稱為Cz-F-OXD)。兩材料分別以傳遞電洞的9-苯基咔唑(9-phenylcarbazole)或是三苯胺(triphenylamine)基團，搭配傳遞電子的噁唑(oxidiazole)基團，使之具有雙性 (bipolar)性質。而在分子設計上，茀(fluorene)九號碳原子以sp3軌域連接傳電子與傳電洞基團，避免造成分子共軛的增加，得到三重態能隙（triplet energy gap, ET）為2.74 eV之主發光體：TPA-F-OXD，Cz-F-OXD。其三重態能隙高於目前常用來作為藍色磷光 ridium(III)bis[(4,6-difluorophenyl)-pyridinato-N,C2’]picolinate（FIrpic, ET = 2.62 eV)。分別以TPA-F-OXD與Cz-F-OXD作為主發光體，摻混7%的FIrpic作為發光層，得到最高外部量子效率17.5和14.7％、最高發光效率32.1和26.3 cd A-1、最高功率效率28.9和18.3 lm W-1。

在B部分中，我們將具有電子傳輸特性的吡嗪(pyrazine)與茀碳-9位置上導入具有電洞傳輸特性的三苯胺共聚合，提升高分子的電荷傳輸特性，接著導入紅色螢光材料4,7-di-2-thienyl-2,1,3-benzothiadiazole (DBT)到高分子主鍊上，得到紅色螢光的PYFTPA-DBT系列高分子，高分子放光波長由459 nm轉移到648 nm。製作成元件後，得到色度座標(0.66，0.34)的飽和紅光元件，其中PYFTPA-DBT10可以得到最佳的效率：最高外部量子效率1.29％與最高功率效率0.63 lm W-1。

Abstract This thesis consists of two sections. In section A we discuss the synthesis and characterization of bipolar hosts for blue electrophosphorescent devices; while in section B we discuss pyrazine-containing polymers as red emitter in electroluminescent devices. In section A, we have synthesized two bipolar hosts applicable in electrophosphorescent devices, namely 9-(3-(5-(4-tert-Butylphenyl)-2- oxadiazoyl)phenyl)-9-(4-diphenylaminophenyl)-fluorene (for the sake of convenience, we will abbreviate this as TPA-F-OXD from now on) and 9-(3-(5-(4-tert-Butylphenyl)-2-oxadiazoyl)phenyl)-9-(9-phenyl-9H-carbazol-3-yl)fluorene (abbreviated Cz-F-OXD from now on). The former material uses triphenylamine as the hole transporter grouped with an oxidiazole group to produce the bipolar characteristic in the material; while the latter uses a 9-phenylcarbazole/oxidiazole group combination to produce the same characteristic. In molecular design, the C-9 atom in fluorene bridge electrons/holes transporting groups via sp3 orbitals preventing the increment of conjugation length. Hence, we can acquire bipolar host with a triplet energy gap (ET) of 2.74 eV: TPA-F-OXD, Cz-F-OXD. This ET is higher than the commonly used blue phosphorescent dopant material- iridium(III)bis[(4,6-difluorophenyl)-pyridinato-N,C2’]picolinate（FIrpic, ET = 2.62 eV). When we use TPA-F-OXD and Cz-F-OXD doped with 7wt% FIrpic as the emitting layer, we obtain a maximum external quantum efficiency of 17.5% and 14.7%, maximum luminous efficiency of 32.1 cd A-1 and 26.3 cd A-1, and a maximum power efficiency of 28.9 lm W-1 and 18.3 lm W-1 respectively. In section B, the novel blue-light-emitting polymers with electron transporting group and triphenylamine pendant groups attached at the C-9 position of the fluorine was synthesized. PYFTPA with both pyrazine and triphenylamine groups demonstrate satisfactory charge injection and charge transporting ability. We then insert a narrow band gap material (DBT) into the polymer. Thus we have obtained a series of polymers named PYFTPA-DBT. Devices based on these polymers emit a saturated red light with Chromaticity coordinates around x = 0.66, y = 0.34. The device using PYFTPA-DBT10 as the emitting layer achieved a maximum efficiency of 1.29% and maximum power efficiency of 0.63 lm W-1.