利用Friedel-Crafts反應於聚乙烯基咔唑與三苯胺衍生物之合成、性質探討及其在電致磷光發光二極體上的應用

Abstract

由於三苯胺具有良好的電荷傳輸性質，因此過去幾年來我們致力於發展三苯胺及其衍生物的探討。在本論文中，我們嘗試著引入三苯胺衍生物到聚乙烯基咔唑當中，期望能有效地提高高分子發光二極體的元件效率以及降低其驅動電壓。由於高分子具有較高的機械強度和熱穩定性，有別於一般有機小分子材料，可減少如相分離、結晶薄膜等問題。因此利用其形態的穩定性，簡易的塗布過程使得高分子材料應用在大面板顯示器中佔有優勢。 在第二章中，我們利用具有光化學活性的三苯胺衍生物作為交聯劑、聚乙烯咔唑作為電洞傳輸材料以及DIAS作為光酸催化劑，將其均勻混和後塗布在ITO基材上，經由紫外線曝光顯影後，交聯的高分子即可固化成膜於基材上，並且可用來製作具有特定放光區域的高分子發光二極體元件，值得一提的是，此最大電流效率可以達到12.1 cd/A。另一方面，我們也進一步地研究在光交聯過程中涉及到的三個反應並行機制，包括光致咔唑偶合的機制，Crivello機制及光酸催化的Friedel-Crafts型機制。 在第三章中，我們利用市售的聚乙烯咔唑與三苯胺或咔唑衍生物進行Friedel-Crafts反應，將三苯胺或咔唑衍生物修飾在聚乙烯咔唑上來作為主發光層材料，並改變其表面功函數，同時維持其三重態能階，可獲得一低驅動電壓為6.5 V （1 cd/m2），在最大電流效率時 (11.5 cd/A)時之亮度可達1287 cd/m2。

The family of triphenylamine (TPA) derivatives has attracted intense research interest during the last few decades due to their excellent charge transporting properties. We attempted to introduce triphenylamine derivatives into poly(N-vinylcarbazole) to improve the performance of PLED. Polymeric hole-transport materials are attractive due to their high mechanical strength and thermal stability. Some problematic phenomena for molecular organic materials such as phase separation or crystallization from the amorphous film, seldom occurs in polymeric films. By taking the advantages of their high mechanical strength, morphological stabilities, good processability, polymeric materials benefit for applications in flexible large-area panel displays. In chapter 2, a photolithographic hole transport material of TriOAc, polyvinylcarbazole (PVK), and diphenyliodonium 9,10-dimethoxyanthracene-2-sulfonate (DIAS, a photoacid generator) has been successfully formulated. After exposure to UV irradiation (λ > 200 nm), a negative tone image was established. This approach can be implemented to PLED applications. The polymeric light-emitting device (PLED) with a turn-on voltage of 12.0 V (1 cd/m2), a maximum brightness of 7087 cd/m2, and a current efficiency of 12.1 cd/A was achieved. Our study reviewed that three parallel mechanisms, including the photodimerization of the carbazole units, the Crivello onium salt sensitization mechanism, and the photoacid catalyzed Friedel-Crafts type electrophilic aromatic substitutions are involved in the photocross-linking process. The next chapter 3, we were interested in the performance of the triphenylamine hung in PVK, which act as a host material in emitting layer. In this study, we intend to make a simple post-functionalization of commercially available PVK, which through the Friedel-Crafts reaction with the triphenylamine and carbazole derivatives. A series of modified PVK work function had been tunable by TPA introducing and maintained the triplet energy state. The PLED device with a turn-on voltage of 6.5 V (1 cd/m2), a maximum brightness of 7412 cd/m2, and a current efficiency of 11.5 cd/A was achieved. In particularly, the brightness could be reached to 1287 cd/m2 at the maximum current efficiency (11.5 cd/A at 13.0 V) and the power efficiency reaches to 2.7 lm/W at 12.0 V. It may be applied to power-saving product and output more brightness at the lower voltage.