非晶態有機半導體及有機發光材料中載子傳輸特性之研究

Abstract

在有機光電元件中，有機半導體之電荷傳輸能力，即載子之遷移率(carrier mobility)是影響元件特性之重要因素，因此量測在有機層中電荷傳輸特性對於元件運作之機制具有重要的意義，同時高載子遷移率材料的研究亦是有機光電半導體中持續的重要課題。在此論文，我們利用飛行時間式電荷傳輸特性量測系統(Time-of-Flight System, TOF)研究新的電荷傳輸材料以及載子在有機薄膜中的傳導特性。我們發現含口夫 喃寡聚物(non-amine-based furan-containing oligoaryls)具有良好電洞傳輸特性，運用此新材料作為有機發光元件之電洞傳輸層時，元件之電特性及發光特性都優於被廣泛使用之芳香胺類電洞傳輸材料。此外，我們揭露三聚芴化物(Terfluorene)具有罕見之高效率雙極性電荷傳遞特性，並比較三聚芴化合物在不同取代基下的電荷傳輸特性，發現具旋環結構鍵結芳香環取代基之三聚芴化合物，不但提供空間阻隔以增加形態(morphology)穩定性及發光效率，並能有效地增加分子間的傳輸能力。利用三聚芴化物之高效率雙極性傳輸特性，我們還發展出一新型TOF Mobility量測架構，利用一薄層三聚芴化物當作載子產生層，成功地量測到各種OLED材料的載子移動率。最後，我們利用三聚芴化物摻雜至聚碳酸酯(PC)，探討具小分子摻雜之聚合物之電荷傳遞特性及物理機制，並發現其具良好雙極性傳輸特性，具有應用於有機光導體的潛力。

Charge transport in organic material plays a crucial role in performances of organic optoelectronic devices. In this thesis, we used the time-of-flight measurement technique to study charge-transport properties of various materials. In the first part of the work, we found that a class of furan-containing oligoaryls that contain no amine moiety could be used as hole-transport materials for OLEDs and devices incorporating such compounds exhibited promising characteristics. In the second part of the work, unprecedented nondispersive ambipolar carrier transport was revealed for a series of terfluorenes. Carrier-transport properties of terflurenes with different types of C9 substitutions were compared. We found that by introducing spiroconjugation between a core chromophore and spiro-linked conjugated substitutions, the bulky substitution not only serves as a spatial hindrance to enhance morphological stability and emission efficiency in the solid states, but can also bridge and enhance intermolecular charge transport, yet still with electronic properties of the core chromophore rather intact. In the third part of the , a new TOF measurement configuration using terflourenes as the charge-generation layer in TOF measurements is discussed. We successfully used this method to measure charge-transport properties of a wide range OLED materials, which otherwise are more difficult to measure by traditional TOF techniques. Finally, we investigated the charge-transporting properties of terflourene-dispersed polymers with different concentrations. Efficient bipolar transport was observed in such MDP systems, indicating potential applications in eletrophotography as organic photoreceptors.