超分子光電材料應用於發光二極體

Abstract

本論文中以開發超分子型電激發光材料與超分子型電洞注入材料為研究主體，內容分為三大主題: 1. 多面體聚矽氧烷為主體之超分子型電激發光材料。 藉由超分子作用力，我們製備出星狀之超分子藍光材料，此星狀超分子，是由4-uracilbutyl-1-methylpyrene ether (U-PY)與octakis[dimethyl(N-(6- acetamidopyridin-2 yl))siloxy] silsesquioxane (ODAP-POSS)形成三點式氫鍵作用力組裝而來，U-PY/ODAP-POSS超分子展現出高量子效率與優異的成膜性，同時氫鍵作用力的連結，也提供了熱穩定性。星狀的U-PY/ODAP-POSS當作發光層作成發光元件有較高之亮度與發光效率相較於U-PY。 另外U-PY/ODAP-POSS可以當作一有效的摻雜物藉由能量傳輸去提升MEH-PPV之發光效率。 2. 新超分子電洞注入/傳輸材料應用於有機發光二極體。 將超分子作用力導入現有之功能性高分子可進一步提升其性質，我們將超分子基團導入共軛高分子poly(triphenylamine-carbazole) (PTC)之側鏈形成物理交聯型高分子(PTC-S)，PTC-S展現出高熱穩定性、抗溶劑腐蝕性、優異的電洞注入與電子阻擋能力。以PTC-S當作電洞注入/傳輸層(HITL)的OLED螢光元件比起以PTC的元件，有顯著性能上的改善。進一步將PTC-S與傳統的電洞注入材料PEDOT:PSS相比，在結構為ITO/HITL/NPB/Alq3/LiF/Al的發光元件下，PTC-S當作HITL的元件比起PEDOT:PSS的元件有1.6倍以上效率的提升，此結果證實運用此超分子電洞傳輸材料有機會進一步提升OLED元件效率。 3. 以氫鍵作用力修飾之電洞注入/傳輸材料應用於有機發光二極體。 此部分，我們比較了不同物理交聯強度在物理性質、光電性質與元件性能上的差異，此篇我們合成了以氫鍵基團為側鏈之電洞傳輸材料(PTC-H)，與PTC-S比較，PTC-H有較高之熱穩定度、較穩定之電化學性質、良好的抗溶劑腐蝕能力與優秀之電洞注入/傳輸能力，因為較強的超分子交互作用力可形成更穩定的物理交聯結構。當PTC-H當作電洞注入/傳輸材料(HITL)運用於OLED螢光元件上，相較於PTC與PTC-S作為HITL，在元件效能上有顯著的提升。由於PTC-H有良好之抗溶劑腐蝕能力，可以運用於溶劑製程製造多層元件，在以Ir(ppy)3為磷光發光的濕式製程元件中，PTC-H為HITL之元件對比PEDOT:PSS的元件有高發光亮度、高外部量子效率與發光效率，顯示了PTC-H有很大的潛力運用於改善OLED之效率。

In this study, we focus on three major subjects which based on supramolecular electroluminescent and hole injection materials 1. A New Supramolecular POSS Electroluminescent Material. A new polyhedral oligomeric silsesquioxane (POSS) core star-like supramolecular blue-light electroluminescent material, 4-uracilbutyl-1-methylpyrene ether (U-PY) / octakis[dimethyl(N-(6-acetamidopyridin-2 yl))siloxy] silsesquioxane (ODAP-POSS) has been synthesized. This U-PY/ODAP-POSS contains eight pyrene chromophore arms formed through complementary uracil-diamidopyridine (U-DAP) pairs and exhibits high quantum efficiencies and good solution processing properties. The photoluminescence spectra of U-PY/ODAP-POSS (50/50) reveal that the color is stable after heating the sample at 150℃ for 1h, in contrast, the pyrene/ ODAP-POSS (50/50) shows significant thermal quenching. An electroluminescence (EL) device based on U-PY/ODAP-POSS exhibits higher maximum brightness and higher luminance efficiency relative to that of the U-PY. In addition, U-PY/ODAP-POSS also behaves as an effective dopant that enhances energy transfer from itself to MEH-PPV. The U-PY/ODAP-POSS-doped MEH-PPV blends exhibit high luminance efficiency, 1.45 times greater than MEH-PPV.

2. A New Supramolecular Hole Injection/Transport Material on Conducting Polymer for Application in Light-Emitting Diodes. A new concept to modify and enhance properties of existed functional polymers through supramolecular interaction has been exploited. In this paper, a new suparmolecular π-conjugated polymer poly(triphenylamine-carbazole) (PTC-S) has been prepared which exhibits high thermal stability, non-corrosion, excellent hole injection and electron-blocking abilities in the solid state owing to the uracil induced physical cross-linking. When the PTC-S is utilized as a hole injection /transport layer (HITL) in a bilayer OLED device, a remarkable improvement in performance relative to the control PTC under similar experimental conditions has been achieved. Further comparison with a control device using a conventional PEDOT:PSS, a trilayer device with PTC-S is approximately 1.6 times higher than that of PEDOT:PSS-based devices. Thus, these results illustrate the opportunity to further imrove the performance of OLEDs and optoelectronic devices.

3. A New Hole Injection/Transport Materials formed through Hydrogen Bonding Interactions for Application in Light-Emitting Diodes. A new concept to modify and enhance properties of existed functional polymers through hydrogen bonding interaction has been exploited. In this paper, A new supramolecular π-conjugated polymer poly(triphenylamine-carbazole) (PTC-H) have been prepared. In comparison with PTC-S, PTC-H exhibit higher thermal stability, higher electrochemical stability, better solvent-resistance ability and more excellent hole injection/transport properties due to the more stable physically cross-linking structure formed by adenine-adenine interactions. When the PTC-H is utilized as a hole injection/transport layer (HITL) in a trilayer OLED device, a remarkable improvement in performance relative to the control PTC and PTC-S under similar experimental conditions has been achieved. Further comparison with a control device using a conventional PEDOT-PSS, solution-processed OLED device using iridium-based triplet emitting layers and physically cross-linked PTC-H films as a HITL show significantly improved performance including higher luminance, higher external quantum efficiency, and higher luminance efficiency, as compared to the control device prepared with PEDOT-PSS. Thus, these results illustrate the opportunity to further improve the performance of OLEDs and optoelectronic devices.