高效率有機發光二極體功能材料之開發

Abstract

近年來，有機發光二極體(Organic Light-Emitting Diode, OLED)顯示技術已成為主要的顯示技術之一，許多配裝OLED之產品也已在業界裡商品化，因此發展高效率OLED的功能材料已成為近期學術研究上探討的重點。在本篇論文中，我們開發了新穎高折射率透明導電陽極與分析其在元件上的光學效應、研究非對稱線性橘紅光熱激活化延遲螢光(Thermally Activated Delay Fluorescence, TADF)材料、以及研究新穎雙價單配位銅錯合物TADF材料。 在本論文第一部分，我們研究使用高折射率透明電極來提升OLED光萃取效率。同時整合折射率高達2.4的透明導體摻鈮二氧化鈦(Titanium Doped Niobium Oxide, TNO)、現今最低折射率的載子傳輸材料與高水平發光偶極矩之發光材料，我們利用簡單的傳統平面OLED結構，實現外部量子效率(External Quantum Efficiency, EQE)超過40% (41.5%)的元件。 在第二部分，我們研究了非對稱橘紅光TADF材料TRZ-SBA-NAI。將TRZ-SBA-NAI摻雜在主體材料當中時呈現橘紅光的放光，並且具有高達87%的光激發光量子效率(Photoluminescence Quantum Yield, PLQY)。同時，TRZ-SBA-NAI分子的線性結構使其具有高水平發光偶極矩比例達88%。最後，TRZ-SBA-NAI的發光元件頻譜峰值為593奈米，EQE高達31.7%，為目前橘紅光TADF元件的最高效率之一。 在本論文的第三部分，我們研究了單價雙配位銅錯合物TADF發光材料MAC*-Cu-DPAC。由於其雙配位的線性結構，使其具有77%的水平發光偶極矩比例，並具有70%的光激發光量子效率。將其整合進元件內，可得到21.1%的高外部量子效率，同時在高亮度1000 nits時依然保有20.1%的高效率，元件頻譜峰值為630奈米，為現在銅錯合物橘紅光與紅光元件表現的最高效率之一。

Recently, organic light-emitting diode (OLED) has been considered as one of the major display technologies. Many electronic products using OLED panels have been commercialized. Therefore, developing high-efficiency OLED functional materials has become an important research topic in academia. In this dissertation, we develop a novel high-index transparent anode materials for OLEDs and study its optical effects on the device efficiency, study an unsymmetrical linear-shape thermally activated delayed fluorescence (TADF) material, and investigate a novel two-coordinate Cu(I) TADF complex. In the first part of this dissertation, we report the adoption of a high-refractive-index transparent electrode as a new avenue for greatly boosting OLED light extraction efficiency. By using the Nb-doped TiO2 (TNO) transparent electrodes with a high refractive index of up to 2.4, along with state-of-the-art low-index organic carrier transporters and highly horizontal dipole emitters, a very high external quantum efficiency of exceeding 40% (41.5%) is realized for simple, conventional planar OLEDs. In the second part, an unsymmetrical TADF emitter of TRZ-SBA-NAI was studied. As doped into the host matrix, TRZ-SBA-NAI exhibited an orange-red emission, together with a high photoluminescence quantum yield of 87%. The linear molecular shape imparted TRZ-SBA-NAI with one of the highest horizontal dipole ratio of 88% for oriented orange-red emitters. Consequently, devices using TRZ-SBA-NAI resulted in high external quantum efficiency of 31.7% with an electroluminescent peak at 593 nm. In the third part of this dissertation, a red Cu(I) complex, MAC*-Cu-DPAC, was studied. Thanks to the linear geometry and the rigid acceptor and donor ligands in a coplanar conformation, the complex not only exhibited a high photoluminescence quantum yield of up to 70% with a sub-microsecond lifetime but also achieved preferentially horizontal dipole orientation. The resulting OLEDs delivered high external quantum efficiencies of 21.1% at maximum and 20.1% at 1000 nits, with a red emission peak at ≈ 630 nm.