寬能隙有機半導體之載子傳輸與光物理特性研究與其元件應用

Abstract

近年來有機發光元件在平面顯示器與照明應用上漸受矚目。然而為了實現高品質的全彩顯示器與照明元件，高效率三原色發光元件是不可或缺的，其中紅光與綠光之有機發光元件逐漸成熟，至於藍光元件則尚待改善，因此寬能隙有機半導體的相關研究便十分重要。 在影響發光元件效率的各種材料特性中，載子傳輸特性與光物理特性對於元件特性有很大的影響。而對於有機半導體材料而言，分子結構的微小差異可能會對材料特性造成巨大的影響。故在本論文中，透過研究不同系列之寬能隙有機分子之光物理與載子傳輸特性，藉由分子構造的探討，希望找出能提升有機寬能隙發光元件效率的分子設計。 本論文中先研究在寡聚物芴化合物(oligofluorene)的九號碳上，不同取代基對載子傳輸特性的影響。接著探討主鏈長度對於茚芴(indenofluorene)化合物之光物理以及載子傳輸特性的影響。本論文次一主題研究了在C3與C6接上不同取代基之咔唑化合物(carbazole)的光物理以及載子傳輸特性，並探討了此載子傳輸特性對元件效率的影響。接著本論文探討了不同架接位置對於寡聚物咔唑化合物的光物理以及載子傳輸特性影響，並發現某些特定寡聚物咔唑化合物具有雙極性載子傳輸特性。本論文最後藉由具有雙極性載子傳輸特性之芴衍生物，實現了藍光與可調色彩之有機發光場效電晶體。

Organic light emitting devices (OLEDs) have attracted wide interest for display and lighting applications in the past decade. Thus high-efficiency OLEDs with three primary color, red, green, and blue, are important for high quality display and lighting applications. Highly efficient red and green OLEDs have become readily available nowadays. However, efficient and stable blue emitters are still highly desired. Therefore the researches of wide-gap organic semiconductors for further developments are very important. Among the characteristics of organic materials, charge-transport and photophysical properties have significant effects on the device performances. In organic semiconductors, slight modification of the molecule configuration could alter the material properties significantly. Therefore, the relation between the molecule configuration and the corresponding charge-transport and photophysical properties is of high interest. In the thesis, we first investigate a series of oligofluorenes with different side-chain substituents on C9 to depict the effects of the side-chain substituents on the charge-transport properties. Subsequently, the charge-transport and photophysical properties of a series of indenofluorenes with different main-chain length are investigated. In addition, we investigate the photophysical and charge-transport properties of a series of triphenylsilyl/trityl-substituted carbazoles. The obtained information is used to explain the corresponding device performance. Further, the photophysical and charge-transport properties of a series of oligocarbazoles with different linking topologies are investigated. Ambipolar charge-transport properties are observed for the first time in some pure oligocarbazole systems. In the end, two fluorene-based materials are employed as the active layers in organic light-emitting transistors (OLETs) to demonstrate blue and color-controllable OLETs.