- 學位論文
有機發光元件載子注入之研究
Investigations of Carrier Injection of Organic Light-Emitting Devices
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摘要
有機發光元件(OLED)在平面顯示器的應用已引發廣大的矚目，然而仍必需要再提高量子效率、功率效率、外部光耦合效率、降低操作電壓與售價等。 本論文共分為兩個部份，第一部份介紹我們與西班牙Murcia大學的Prof. David Curiel Casado共同開發了一系列以咔唑基團(Carbazole)為主要結構的新穎多功能有機材料(MMM-series)，透過完整地探討材料特性，我們了解到MMM-series具有相當高的潛力可作為紅色磷光的電洞傳輸層材料與主體材料，因此在使用MMM-series為電洞傳輸層與發光層的縝密測試中，以Ir(piq)2(acac)作為客體材料的磷光有機元件便具有出色的表現，最高效率在三層與雙層元件分別達到12.2% (8.7cd/A and 9.3lm/W) 與 9.1% (6.3cd/A and 6.2lm/W)，另外在作為電洞傳輸層與發光層的分析比較可發現，新穎多功能有機材料MMM-series便比商用材料NPB更為優異，因此我們推斷以carbazole-base為基底的MMM-series在紅光磷光有機發光元件將備受矚目。 論文的第二部份，我們從第一部份得到的結果出發，在得知降低電洞傳輸層與主體間的注入能障將可有效的降低操作電壓，而為了再次佐證此想法，我們在p-i-n型的有機發光元件中使用兩個寬能隙且具有雙載子傳輸特性的主體材料mCP和TCz1，希望藉由其材料特性進行更深入的分析與探討，另外，也希望在導入導電性摻雜於傳輸層中可有效的簡化p-i-n型的元件結構，最後經由本論文兩部份的研究努力，證實p-i-n型的有機發光元件在使用TAPC與TCz1為電洞傳輸層和主體材料時，在1000cd/m2的實用亮度，其操作電壓可大幅度的降低至3.5V，而如此令人振奮的優異表現，使我們相信如此新穎的p-i-n型有機發光元件在未來勢必擁有高度的照明應用潛力。
關鍵字
載子注入並列摘要
Organic light-emitting diodes (OLEDs) have drawn widespread attention due to their promise for applications in displays. However, OLED still needs to improve on its quantum efficiency, power efficiency, out-coupling, lower operation voltage and cost. This thesis is divided into two parts. In the first part, we cooperated with Prof. David Curiel Casado from University of Murcia to develop a series of carbazole-based multi-functional materials, named as MMM-series. Through elaborately investigating the materials’ characteristics, we realized that the MMM-series have highly potential for employing as hole-transport material and host material for red phosphors. Comprehensive tests as the HTL and emitting host in Ir(piq)2(acac)-based PhOLEDs yielded outstanding performances, with maximum efficiencies of 12.2% (8.7cd/A and 9.3lm/W) and 9.1% (6.3cd/A and 6.2lm/W) achieved in trilayer and bilayer architectures, respectively. The novel materials exhibited superior performances to those of devices using NPB as the Hole transport layer or host. Therefore, we conclude that these carbazole-based hole transport materials are indeed highly promising for employment in red phosphorescent OLEDs. Based on the results of the first part, we realized that the mitigated energy barrier between HTL/host interfaces can help to decrease the driving voltage. To further confirm this idea for p-i-n OLEDs, two bipolar host materials with wide triplet energy gap, mCP and TCz1, were employed for fair comparisons. Furthermore, the conducting materials were doped into the carrier transport layer to simplify the architecture. Through comprehensive studies, the experiment results indeed consisted with the conclusion of the first part. The practical luminance of 1000cd/m2 under 3.5V driving voltage can be obtained by using TAPC and TCz1 as the hole transport and host materials, respectively. Buoyed by the encouraging results, we believed that this novel design of p-i-n OLEDs has highly potential for the lighting applications.
參考文獻
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