六配位藍光鋁錯合物材料的合成及在有機電激發光之應用

Abstract

本論文以濕式製程之螢光材料開發及其在有機電激發光元件之應用為主軸，並以tris(8-hydroxyquinolinato)aluminum (Alq3) 結構為主體，進行該衍生物的開發與製備，並發展出功能性、新穎性且寬能隙主發光體之濕式電激發光材料；根據ZINDO半經驗式預估方法，8-氫氧基喹嚀環上第五位置導入拉電子基將降低最高佔據分子軌域能階，並使錯合物螢光波長變短，因此在論文研究中，我們將強拉電子性的硫醯胺基導入於8-氫氧基喹嚀，並探討一系列取代基對六配位鋁錯合物的各項物性及化性影響，以及衍生化合物的分子設計與光電特性。 在第三章研究中，我們首度利用取代基改良成功的克服sulfonyl substituted quinoline的溶解度，並發展出可濕式塗佈製程之六配位小分子藍光錯合物tris(5-N-ethylanilinesulfonamide-8-quinolato-N1,O8) aluminum (III) [Al(Saq)3]。我們也藉由單晶結構剖析、熱性質分析及元件製備，完整的探討Al(Saq)3之塗佈成膜機制及其在溼式製程之潛力。 在第四章研究中，我們藉由活化複體生成機制，以主發光體材料tris(5-mestylsulfon-8-hydroxyquinolato) aluminum (III) [Al(MSq)3]與N,N-diphenyl-N,N’-bis(methylphenyl)-(1,1’-biphenyl)-4,4’-diamine (TPD)掺混薄膜發展出濕式白光元件，並在單一發光層結構中，我們獲得雙波段白光元件，且其最佳白光色度座標值可達到1931 CIEx,y (0.33，0.33)。 在第五章，根據Al(Saq)3單晶結構分析及昇華實驗中，Al-N鍵長並未如文獻報導所陳述的將受到強拉電子團-磺醯胺基的效應變長而導致無法昇華，並首度證明六配位sulfonamide substituted aluminum錯合物確實可以昇華，且可以熱蒸鍍方式製作多層結構元。因此，在第六章的研究中，我們製備了一系列不同屬性sulfon取代基之Alq3衍生物，藉由一系列1H NMR、單晶結構及真空熱重量分析，完整探討這類錯合物的物理化學特性，並歸納出整個材料研究系統無法昇華機制。 根據Al(Saq)3發光元件特性剖析基礎，我們在第七章以化學方法將電洞傳輸材料carbazole導入Al(Saq)3分子側鏈。在該研究中，我們針對濕式製程與材料特性剖析中發現，適度的導入電洞傳輸分子，將可以提升發光核心的元件效能，且改善螢光活化複體及電激發光程序所生成的electroplex。本論文之所有詳盡研究內容將在各章節中逐一深入探討。

This thesis is mainly focused on the development and synthesis of solution-processible organic light-emitting materials based on tris(8-hydroxy- quinolinato)aluminum, Alq3. According to the semiempirical approach of Zerner International Neglect of Differential Overlap (ZINDO) theory, reducing electron density from the phenol ring of 8-hydroxyquinoline at C5 will lower the highest occupied molecular orbital (HOMO) energy level of Alq3-based materials and widen their energy band gap of the transition. Based on this theory, we introduced stronger electron- withdrawing groups, such as sulfonamides at the C5 position of 8-hydroxyquinoline to synthesize the six-coordinated aluminum chelates, which emits in blue. In addition, we also explored the substitute effect, chemical and physical properties of these derivatives. Their molecular design and corresponding optical characteristics related to OLED applications were also investigated in this thesis. In chapter 3, we have successfully modified the substituent to overcome the dissolution problem in sulfonyl substituted quinoline and come up with a solution-processable blue chelate tris(5-N-ethylanilinesulfonamide-8-quinolato-N1,O8) aluminum (III) [Al(Saq)3]. With the help of single crystal analysis and thermal property analysis, the potential and performance of device fabrication using Al(Saq)3 was investigated. In chapter 4, white light emitting devices were fabricated by solution process. The active layer of the device was consisted of the blend of the host material tris(5-mestylsulfon-8-hydroxyquinolato) aluminum (III) [Al(MSq)3] and N,N-diphenyl-N,N’-bis(methylphenyl)-(1,1’-biphenyl)-4,4’-diamine (TPD) was fabricated by solution process. Via the formylation of exciplex during electroluminescence process, a two-element white device was obtained, and the optimal chromaticity was achieved nearly at 1931 CIEx,y (0.33, 0.33). In chapter 5, according to the single crystal analysis and sublimation experiment of Al(Saq)3, the bond order of the Al-N will not be affected by the strong e-withdrawing group of the sulfonamide substitute. This evidence further revealed that the derivate failed to sublimate is not induced by Al-N. Based on this result, we have also successfully demonstrated the feasibility of mer-Al(Saq)3 in light-emitting device by thermal evaporation. In chapter 6, we synthesized a series of Alq3 derivates with different sulfon substitutents. Using x-ray diffraction, 1H NMR and thermal gravity analysis the physical and chemical attributes of these chelates were investigated and well characterized. In this chapter, we also explored the mechanism of thermal decomposition during sublimation process. According to the characteristic analysis of Al(Saq)3–based devices, we introduced the hole-transporting moiety, carbazole into Al(Saq)3 to produce a functionalized supramolecule by utilizing synthetic approach in chapter 7. In this topic, we found that with the proper incorporation of hole transport material, the performance of the device can be improved and also suppress the electroplex that was produced during electroluminescence process. Detailed discussions regarding to the study will be presented in this thesis.