含有□雙□雜環材料的合成與性質研究

Abstract

本論文我們選擇於fluorene 碳-9位置，接上剛硬的OXDs基團，合成具有高玻璃轉移溫度及良好熱穩定性的高分子PF-OXD (A 部分) 與小分子F-OXDs (B 部分)。 在A 部分中，因為PF-OXD的高玻璃轉移溫度 (213 ℃) 使其薄膜於氮氣下加熱至150 ℃20小時後，並未在吸收/發射光譜上有明顯改變。由於PF-OXD不但能有效抑制堆疊效應與激發複合體發光，而且主鏈與側鏈間有效率的能量傳輸機制，使得雙層PLED元件於10.8 伏特時，達到最大亮度2770 cd/m2；於7.4 伏特時，得到最大外部量子效率0.52 %，比未經OXD修飾的POF具有較佳的電子電洞再結合效率。 在B 部分中，小分子F-OXDs 的玻璃轉移溫度(128-155 ℃)及其他熱性質都比2-(4-diphenylyl)-5-(4-tert-butylphenyl)- 1,3,4-oxadiazole (PBD) 優異。此外，透過OXD取代基的修飾，我們可以調整它們的能階位置與大小；而且從循環伏安法測量發現，它們具有較低的LUMO能階(2.46-2.84 eV)，此將有助於電子的注入與傳導，使它有機會成為藍光的主發光體或電子傳輸材料。

A novel fluorene-based oxadiazole-containing polymer (PF-OXD, Part A.) and a series of fluorene derivatives (F-OXDs, Part B.) of high glass-transition temperature was successfully synthesized by introduction of bulky and rigid oxadiazole containing substituents at C-9 position of fluorene units. In Part A., PF-OXD possesses a very high Tg (213 °C) and very good thermal stability due to its rigid cardo-linkage. In contrast to POF, prolonged heating of PF-OXD thin film (150 °C for 20 h) resulted in no changes in morphology and emissive color. The luminance reaches 2770 cd/m2 at a drive voltage of 10.8 V and the maximum external quantum efficiency is 0.52 % with a bias of 7.4 V. The improved device performance over that of POF may be due to better charge injection and transport from PF-OXD and the efficient energy transfer from OXD side chain to the polyfluorene main chains. In Part B., those oxadiazole-containing small molecules F-OXDs are able to form stable glasses with higher glass transtion temperatures (128-155 ℃) and better thermal stabilities than 2-(4-diphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD). The alternated incorporation of OXD substituents in F-OXDs leads to the tunability of the HOMO/LUMO levels and energy band gaps. Cyclic voltammetry studies reveal that these small molecules possess low-lying LUMO energy levels ranging from 2.46 – 2.84 eV and wide energy band gaps and may be promising candidates as electron-transporting blue hosts.