高效率磷光聚茀材料之合成與性質研究及其元件上的應用

Abstract

我們成功地將磷光金屬錯合物以化學鍵結的方式接在聚茀高分子主鏈上，合成了一系列單一成分的高分子發光二極體材料，並詳細探討其化學合成、光物理性質以及元件表現。藉由在聚茀高分子主鏈上導入具有電荷傳輸特性的側基，有效幫助電荷注入或傳輸到發光層，增加元件效率；同時也提高了高分子的熱穩定性。 本主題共分為四個章節。首先，我們將銥金屬錯合物Ir(dpq)2acac導入高分子PFECzOXD中，合成COF-Ir系列紅光高分子。PFECzOXD同時具有carbazole (Cz)及oxadiazole (OXD)側基，增加了電荷注入與傳輸能力，使電荷有效的在發光層中再結合而提升元件效率。在製成元件後，COF-Ir500展現了良好的效率，在3.5 mA/cm2電流密度下，最大外部量子效率(EQE)為1.8 %，同時最大放光效率為1.7 cd/A。 第二、三章我們將三種鋨金屬錯合物Os(fppz)2(PEt2BP)2、Os(fptz)2(PEt2BP)2以及Os(bftz)2(PEt2BP)2分別與藍光聚茀高分子PF-TPA-OXD結合，合成TOF-Os、TOF-tOs和TOF-terOs等三組紅色磷光高分子。PF-TPA-OXD含有具電洞傳輸能力的triphenylamine (TPA)及具電子傳輸能力的oxadiazole (OXD)二個側基，可以增進電荷注入及傳輸，使這一系列含鋨金屬錯合物的磷光聚茀材料展現極佳之元件效率。 TOF-Os100在電流密度2.4 mA/cm2時得到最大外部量子效率(EQE)為10.2 %，同時最大放光效率為10.5 cd/A；TOF-tOs150在電流密度3.5 mA/cm2時得到最大外部量子效率(EQE)為11.1 %，最大放光效率為11.2 cd/A；TOF-terOs150在電流密度3.5 mA/cm2時得到最大外部量子效率(EQE)為15.4 %，最大放光效率為23.0 cd/A，是目前效率最高的紅色磷光高分子。 最後一部分，我們合成了同時具有螢光及磷光混成放射的高效率單一白光高分子材料TOF-BT-terOs。該材料是以聚茀高分子PF-TPA-OXD作為主發光體提供藍光；主鏈上導入客發光體綠色螢光分子benzothiadiazole (BT)以及紅色磷光分子Os(bftz)2(PEt2BP)2共聚組成白光高分子，其中TOF-BT01-terOs02藉由benzothiadiazole (BT)及Os(bpftz)2(PPhEt2)2的含量調整，而達到涵蓋可見光區域的白光放射。其最佳的元件表現在電流密度3.4 mA/cm2下，最大外部量子效率(EQE)為4.9 %；最大放光效率為9.3 cd/A；最大亮度7400 cd/m2；並且在操作電壓9 V的驅使下，其CIE座標為(0.37, 0.30)相當接近標準白光(0.33, 0.33)的位置。

Highly efficient phosphorescent polymers are realized by covalently attaching red phosphors into the backbone of polyfluorene in different molar content. In this report, the synthetic routes and chracteristics of these resulting copolymers are discussed in detail. The prescence of charge-transporting pendants improves carrier injection and transport so that these copolymers perform an outstanding device efficiency and good thermal stability In the first part, we have developed red-emitting polymer (COF-Ir) through the incorporation of Ir(dpq)2acac moieties into the backbone of a polyfluorene, which contains hole-transporting carbazole (Cz) and electron-transporting oxadiazole (OXD) pendant groups to improve the charge injection and balance charge recombination. Among these copolymers, COF-Ir500 shows the best device performance which reached a maximum external quantum efficiency of 1.8 % and the maximum luminescence efficiency of 1.7 cd/A at the current density of 3.5 mA/cm2. Secondly, we synthesized three types of phosphorescent copolymers (TOF-Os, TOF-tOs, and TOF-terOs) by chemically doping different Os complex (Os(fppz)2(PEt2BP)2、Os(fptz)2(PEt2BP)2 and Os(bftz)2(PEt2BP)2 into the polyfluorene, which contains hole-transporting triphenylamine (TPA) and electron-transporting oxadiazole (OXD) pendant groups. We found that the device based on TOF-Os100 shows the best performance with the maximum external quantum efficiency of 10.2 % and the maximum luminescence efficiency of 10.5 cd/A at the current density of 2.4 mA/cm2；TOF-tOs150 shows a maximum external quantum efficiency of 11.1 % and the maximum luminescence efficiency of 11.2 cd/A at the current density of 3.5 mA/cm2；TOF-terOs150 reaches a maximum external quantum efficiency of 15.4 % and the maximum luminescence efficiency of 23.0 cd/A at the current density of 3.5 mA/cm2. In the last topic, we demonstrate a strategy to generate an efficient white-light emission through fluorescence and phosphorescence hybrid emission from a single polymer (TOF-BT-terOs). Polyfluorene is served as the blue-emission component; benzothiadiazole (BT) and the osmium complex Os(bftz)2(PEt2BP)2 are served as green- and red-emissive chromophores. By adjusting the feed ratio of benzothiadiazole (BT) and Os(bftz)2(PEt2BP)2, the white-light emission covering entire visible region was achieved. TOF-BT01-terOs02shows a maximum external quantum efficiency of 4.9 %； the maximum luminous efficiency of 9.3 cd/A at the current density of 3.4 mA/cm2 and the maximum luminance of 7400 cd/m2 with the CIE coordinates of (0.37, 0.30) at 9 V.