金屬-有機-金屬結構應用於有機發光元件之優化

Abstract

有機發光元件(organic light-emitting diode, OLED)具有低損耗功率、寬視域角、對比度佳等優勢，已大幅應用於照明及顯示器產業。由於傳統白光OLED的藍光材料壽命和效率會比紅光及綠光材料略差，所以藉由壽命長的綠光材料，利用金屬-有機-金屬的結構產生藍位移現象後，有效地取代藍光材料，成為新一代的照明技術。 本篇論文中，使用金屬-有機-金屬(MDM)的結構作為有機發光元件，由於此結構有如微共振腔結構，故利用Fabry-Perot共振腔的方法設計該結構的光學長度，且求得所允許之模態下的電子傳輸層(ETL)厚度，搭配不同週期的光柵結構進行模擬，分析不同電子傳輸層厚度之平面結構的出光效率及發光頻譜，並與具不同週期之光柵結構相比較。 在研究結果中，發現在平面結構下，隨著電子傳輸層厚度的增加，出光效率會隨之下降，發光波長會往長波長移動，最佳的電子傳輸層厚度為40 nm，出光效率可達16.1%。當具有不同週期之光柵結構，出光效率會以週期為416.52 nm，高度為70.67 nm最好，與平面結構相較下，由於能被激發的波段有限，導致能量困在結構內，所以出光效率無法有效提升。

OLED possess many advantages such as low power loss, wide viewing angle and high contrast ratio. It was widely applied in lighting and display industries. Due to the lifetime and efficiency of the blue light material in conventional white OLED being poorer than the red light and the green light material, the long-life green light material becomes the key lighting technology of the new generation. This study uses the long-life green light material and takes advantage of the characteristic of the metal-dielectric-metal structure to induce a blue shift to produce an overall white light. In this work, the metal-dielectric-metal structure (MDM) is used as the organic light-emitting device. The optical length of the structure forms a Fabry-Perot cavity consists of the MDM structure. This study makes use the matching between different grating structure periodicities and simulates the modes within the electron transport layer (ETL) thickness to analyze the light efficiency and the emission spectrum. Different ETL thicknesses are also compared with the different grating structure periodicities. In the results, this study finds that increasing the ETL thickness leads to a decrease in the light efficiency. The emission wavelength shift to longer wavelengths, and the emission color change from blue-green to green in the optimal condition that the ETL thickness is 40 nm, with light efficiency 16.1%. With different grating periods, the best light extraction efficiency is achieved for grating period of 466.52 nm, and the height is 70.67 nm. In comparison with pure planar structure, since the excited spectrum bandwidth is narrower, more the energy is trapped inside the structure, leading to limited improvement in the light efficiency.