微光學膜對有機發光元件光學特性改善之研究

Abstract

有機發光元件具有高對比、反應時間短、自發光、成本低廉以及可以與各種材質的基板整合的特性，使得它在平面顯示器與固態照明等方面都受到各界的矚目，然而，高效率的有機發光元件仍然是大家努力的方向，其中，有機發光元件的出光耦合率更是一個重要的議題。 在本篇論文中，我們製備了兩種不同的光學膜：微透鏡陣列(microlens array)與微顆粒散射膜(micro-particle diffuser film)。我們將微透鏡陣列應用於不同顏色的有機發光元件上，其中將微透鏡陣列貼附於白光有機發光元件上，可以提升元件的外部量子效率23%，提升亮度47%，並且可以有效改善白光有機發光元件各視角光強度的分佈。 將微共振腔結構結合有機發光元件可以得到較好的顏色飽和度以及較高的亮度，然而微共振腔有機發光元件的顏色表現與元件效率通常無法同時被改善。我們將微顆粒散射膜貼附於微共振腔上發射型有機發光元件上，不但提升元件的外部量子效率與電流效率為傳統下發射型有機發光元件的2.1倍與2.9倍，而且改善元件各視角光強度，使其更接近理想的Lambertian分佈，但是仍然保持微共振腔有機元件良好的顏色飽和度。 由於光學膜並不直接與有機元件接觸，因此應用光學膜於元件上不但可以提升元件效率與顏色表現，而且不影響元件操作，而且光學膜的製備簡單、價格低廉，並且與有機發光元件的製程是完全相容的。

Organic light-emitting devices (OLEDs) are very attractive for applications in flat panel displays and solid state lighting due to their high contrast, fast response time, self-emissive nature, low cost and easy integration with various substrates. However, the out-coupling efficiency of OLEDs is low because of various optical trapping mechanisms such as the total reflection loss. The OLEDs can be made more efficient if one can improve the out-coupling efficiency of OLEDs, making OLED more suitable in various applications. In this thesis, we fabricated two different kinds of micro-optical films: microlens-array and micro-particle diffuser film. We applied microlens array to OLEDs of different color. In white organic light emitting devices, by integrating with micorlens array, the external quantum efficiency can be enhanced by 23%, and the brightness can be enhanced by 47%. Moreover, the emission pattern of the white OLED become more Lambertian with microlens arrays. The organic light-emitting device (OLEDs) with microcavity structures is often used to improve color saturation and to enhance device brightness. However, the device efficiencies and color performances of the device usually cannot be achieved at the same time. By integrating microcavity top-emitting OLEDs with micro-particle diffuser films, the external quantum efficiency can be enhanced by 2.1 times, the cd/A efficiency can be enhanced by 2.9 times compared to the conventional bottom-emitting OLEDs. With diffuser films, the angular dependence of the top-emitting OLEDs becomes closer to the Lambertian distribution. Without direct contact with the device, OLEDs integrated with micro-optical film not only enhances the device efficiencies but also improve the color performances. This approach is simple, effective and highly compatible with OLED fabrication.