內嵌散射膜改善有機發光元件光耦合效應之研究

Out-coupling efficiency improvement of OLEDs by using an embedded nanocomposite scattering film

張國彥(Kuo-Yan Chang)

指導教授 ： 張志豪

元智大學/電機通訊學院/光電工程學系/碩士(2012年)

摘要

典型的下發光有機發光元件，依照光被侷限的區域分為四種模態，分別為輻射模態、基板模態、ITO/有機層-波導模態和表面電漿模態，其中輻射模態僅佔四種模態的25 %，因此元件效率遲遲無法提升。而內部光萃取結構已被證實能有效減少波導模態比例，並且增加基板模態與輻射模態的比例。

故我們著重於使用內部結構改善光萃取效應，本論文利用混合奈米顆粒與透明光阻製作內嵌式散射膜，不同粒徑的奈米顆粒擁有不同功能，較大的顆粒的TiO2擁有散射功能，可以有效防止光經由反射回到透明導電膜，另一方面，較小直徑的TiO2則擁有提高透明光阻折射率，降低散射膜與透明導電膜的界面反射，利用混合的散射層可製造出在亮度在1000cd/m2下，相較於傳統元件外部量子效率提昇2.29倍。相較於目前先進的技術，我們的高效率和製作方法都能將白光有機發光元件更向商品化的目標推進。

關鍵字

有機發光元件 ； 內嵌散射膜 ； 奈米粉末

並列摘要

In view of the present bottom-emitting OLED architecture, the generated light is classified into four types of modes in OLEDs: radiation mode, substrate mode, ITO/organic-waveguided modes, and surface plasmon mode. The radiation mode generally makes up only about 25% of the light generated, and typically does not contribute significantly to the flux of the device. Fortunately, it has been demonstrated that internal extraction structures(IES) can be introduced in OLEDs to decrease the ratio of the waveguide mode and simultaneously increase the ratios of the substrate and radiation modes.

Thus, we focused on the light extraction by internal extraction structures. In this thesis, nanoparticles combined with transparent photoresist(TPR) were used to form an embedded nanocomposite scattering layer. Nanoparticles with different sizes possess distinct functions. TiO2 particles with a greater diameter were used to create scattering and thus diminish the light reflection from glass substrate back to the ITO layer. On the other hand, the refractive index of TPR can be increased by dispersing the small-size TiO2 into TPR, which magnifies the amount of light entering from ITO layer into the scattering layer. By employing scattering layer with mixed nanoparticles, the external quantum efficiencies of blue phosphorescent OLEDs were about 2.29 times higher than that of control device at 1000cd/m2. This highly expedient and effective technique is undoubtedly comparable with state-of-the-art methods and can potentially push WOLEDs close to commercialization.

並列關鍵字

OLED ； Out-coupling ； nanocomposite scattering film

參考文獻

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