有機發光二極體高分子發光材料的合成與性質研究

Abstract

本論文分為三部分，分別針對PPV衍生物、聚茀高分子衍生物與金屬橘紅色磷光高分子材料之合成、性質與元件做探討。 在A部分中，我們以PPV為主鏈，在2,5-位置導入Mullen type的Dendron取代基，此龐大的側鏈基除了提升高分子的熱穩定性，亦減少主鏈因堆疊而降低發光效率、影響光色純度。因此，在薄膜熱處理後，仍維持發光效率及光色的純度，其電激發光亦不隨電壓增加而改變。 在B部分中，我們在fluorene碳九位置導入xanthene，成spiroxanthenefluorene中心剛硬的sp3正交結構，此高分子除了修飾聚茀因平面結構所造成的物理缺陷、提升Tg，亦避免因熱、UV照射或操作電壓下產生化學缺陷而影響材料的色純度及穩定性。此外，也將具有電洞傳輸能力的carbazole側鏈基導入Spiroxanthenefluorene中，對於驅動電壓的降低及效率的提升有明顯的助益。 在C部分中，以高效率藍光高分子材料PF-TPA-OXD當作骨架，將橘紅光的磷光材料Ir(piq)2cdp以化學性摻混導於側鏈，並藉由FÖrster能量轉移及電荷捕捉機制將能量傳輸到磷光側鏈上，再由此部分發橘紅色磷光。此外，我們也製成物理混摻之元件，來模擬化學混摻的比例，發現以化學混摻之磷光高分子由於分散性佳，可避免相分離，因此在元件操作下有較穩定及出色的表現。

This thesis is divided into three parts regarding the synthesis and characterization of poly(phenylenevinylene) derivatives, poly[spiro(fluorene-9,9’-xanthene) and polyfluorene derivatives grafted with cyclometalated iridium complexes. We also report the fabrication and performance of electroluminescence devices based on these materials. In part A, we have synthesized a dendronized polymer, PPV-PP, that consists of a conjugated poly(p-phenylenevinylene) backbone upon which are appended pentaphenylene dendritic wedges. As a result of incorporating the dendritic pentaphenylene pendent groups, which reduce the strength of interchain interactions and suppress the formation of excimers, PPV-PP is soluble in common organic solvents and exhibits high photoluminescence efficiency in the solid state. Even after thermal annealing at 150 ℃ for 20 hours, a long wavelength emission band by the excimer formation was not observed. In addition, devices based on this polymer exhibit stable EL spectra which are independent of applied voltages. In part B, we have synthesis a polyfluorene containing spiroxanthene pendant groups, where the planes of the xanthene and fluorene lie perpendicular to each other and are connected by a tetrahedrally bonded carbon atom. The incorporation of xanthene into the polyfluorene not only prevents the formation of aggregates and excimers in the solid state, but also inhibits the formation of a chemical defect induced by thermo-, photo-, or electro-oxidative degradations. We also introduced the two carbazole side groups into the spiro-polymer to lower the turn on voltage and enhance the quantum efficiency EL devices. In part C, two orange-light-emitting copolymers (TOFR series) grafted with Ir(piq)2cdp have synthesized. These two copolymers emit organic light through FÖrster energy transfer and charge trapping mechanisms. Devices based on TOFR series show better stability and external quantum efficiency in comparison with devices based on PF-TPA-OXD blended with iridium complex.