光學濾波器應用於有機發光二極體與光伏整合元件之效能提升

Abstract

有機發光二極體的許多特性，例如:自發光，反應時間快速，可撓性等，使其可能成為未來顯示器的主流技術之一。然而，有機發光二極體在戶外的對比度是一項需要克服的問題。因此，許多研究團隊致力於相關的研究，例如結合偏振器，以及結合反射式液晶來提升對比度的方法。由於近年環保意識抬頭，眾多方法之中，一項結合能源再利用的設計—結合薄膜太陽能電池，相較於其他方法更有機會能夠成為未來的主流技術。雖然結合太陽能電池的有機發光二極體可以增加對比度，也能將吸收的光能回收成為電能，但是同時也使其發光效率降低百分之五十，必須要克服此問題，這種新型元件才能成為綠能科技主流技術。 本論文的主要研究為設計光學結構，使其產生理想的反射頻譜，目的在於針對有機發光二極體的發光頻段提高反射率，以增強其出光效率。同時讓其他部份頻段的光穿透，維持較低的總反射量，進而維持高對比度。本論文從分析前人的研究開始，建立模型，設定假說，設計出光學濾波器，最後進行整合元件的分析及討論。 光學濾波器的部份，本論文討論了兩種常見的結構。其一為布拉格反射鏡(Distributed Bragg Reflector)，其二為導模共振濾波器(Guided Mode Resonance Filter)。設計布拉格反射鏡的部份，利用解析解設計理想的反射強度及頻寬。導模共振濾波器則無解析解，本論文利用參數與對應頻譜的相對關係做參數掃描，利用最簡單的結構，設計出理想的反射頻譜。 最後，比較兩種濾波器的效能以及作為全彩顯示器的可能性，並且討論兩種光學濾波器未來實作的可行性分析。

Organic light emitting diode (OLED) is becoming a major technique for display technology due to many properties such as self-emissive, fast response time and flexible application. However, poor outdoor contrast ratio of OLED is an important issue to be discussed. Therefore, many efforts were devoted into related researches, such as integrating polarizer and reflective liquid crystal with OLED. Recently, due to the promotion of environmental protection consciousness, an energy-recycling device—thin-film solar cell integrated OLED, would become an attractive solution to contrast ratio problem among many other solutions. Although the integrated device of OLED and solar cell would provide contrast ratio enhancement and energy recycling ability, it would also decrease the luminous efficiency to about 50% as compared to the original OLED. This would become an obstacle to develop this eco-friendly technology. In this thesis, we focus on designing optical filters with a desired spectrum. By enhancing the OLED emission reflection, and suppress other band besides OLED emissive band, the filters would enhance the OLED emission while keep high contrast ratio. This thesis starts from verifying formal research and building optical simulation models, followed by proving assumptions and designing optical filters. In the last part, we made some analysis and discussions about the effect of filters. By considering optical filters, we discussed two common optical structures, i.e., the distributed Bragg reflector (DBR) and guided mode resonance (GMR) filter. We use analytical solution to obtain ideal reflectivity and suitable bandwidth. For the GMR part, we scan different parameters by using the relationship of parameters and reflection spectrum to obtain an ideal spectrum with a simple structure. Finally, we compare the two optical filters and discuss the possibility of full color display realization. Moreover, we discuss the possibility of applying the filters for reflective display devices.