合成含銥錯合物之離子性聚芴衍生物及其在有機發光元件之應用

Abstract

本研究之目的在合成出含黃光或紅光銥錯合物之離子性聚芴衍生物，探討其熱、光學及電化學性質，接著應用於白光電化學電池元件。本研究同時合成出含黃光銥錯合物之中性聚芴衍生物以作為對照。苯基吡啶或異喹啉吡啶分別被選為銥錯合物之配體以形成黃光或紅光客體材料。利用核磁共振光譜及傅立葉轉換紅外線光譜確認材料已完成離子化及離子置換反應。化學分析電子光譜結果說明銥錯合物已成功引入高分子主鏈。熱重分析顯示當Br−置換為PF6−基後，可抑制霍夫曼脫去反應並大幅提升離子高分子之熱穩定性。吸收光譜顯示含有Br−之離子高分子在甲醇會產生藍位移，而含有PF6−之離子高分子在乙腈中會產生藍位移。此因高分子在該溶劑之溶解度較高造成高分子鏈之間距離較遠，分子間作用力降低所致。放射光譜顯示與黃光或紅光銥錯合物進行共聚之聚芴高分子，除了在430 nm出現聚芴主峰，也分別於540或620 nm出現三重態放光。電化學分析顯示含PF6−之離子高分子相較於中性高分子其氧化電位明顯降低，因而造成材料最高已填滿分子軌域及最低未填滿分子軌域有所提升。 本研究利用離子性及中性聚芴分別作為電化學電池發光元件及高分子發光元件之主動層。以離子性聚芴製作之白光電化學電池發光元件，可得到低操作電壓、高亮度及高效率的特點，且不需額外加入鹽類或聚氧化乙烯。高分子發光元件的最大亮度為595 cd/m2，元件效率約為0.043 cd/A，CIE’1931座標落於(0.28, 0.37)，光色接近白光範圍。以上結果說明這些離子性聚芴材料具有應用於白光固態照明領域之潛力。

The goal of this research is to synthesize ionic polyfluorene derivatives containing yellow or red-light iridium complexes for investigation of thermal, optical, and electrochemical properties, followed by applying in white light-emitting electrochemical cells (LEC). A neutral polyfluorene derivative containing yellow-light iridium complex was also synthesized for comparision. Phenylpyridine or isoquinolinylpyridine were selected as ligands to form yellow or red-light iridium complexes, respectively. Nuclear magnetic resonance and Fourier transform infrared spectroscopies were used to confirm ionization and ionic exchange reaction of materials. Electron spectroscopy for chemical analysis demonstrated that iridium complexes were successfully introduced into polymer main chain. Thermogravimetric analysis showed that Hofmann elimination was prohibited and thermal stability of polymers was significantly improved by replacing Br− with PF6− counterions. UV-visible absorption spectroscopy showed that Br−-containing ionic polymers generate blue shift in methanol, while PF6−-containing ionic polymers generate blue shift in acetonitrile. This is because higher solubility of polymers was found in the above solvents, resulting in longer distance and smaller molecular interaction between polymer chains. Photoluminescence spectroscopy indicated that the polyfluorenes copolymerizing with yellow or red-light iridium complexes showed triplet emissions at 540 or 620 nm, respectively, in addition to main emission of polyfluorene at 430 nm. Electrochemical analysis showed that oxidation potentials of PF6−-containing ionic polymers were significantly decreased, resulting in increase in highest- occupied molecular orbital and lowest-unoccupied molecular orbital of materials. In this research, ionic and neutral polyfluorenes were utilized as active layers in LECs and polymer light emitting devices (PLEDs), respectively. By using ionic polyfluorenes, white-light LECs showed advantages of low operation voltage, high brightness, and high efficiency without adding additional salts or poly(ethylene oxide). The PLED showed the maximum brightness of 595 cd/m2, the current efficiency of 0.043 cd/A, and CIE’1931 at (0.28, 0.37) that approached white light area. The above results demonstrate potential applications of these ionic polyflourene materials in white solid-state-lighting area.