有機發光二極體在小尺寸顯示器的市場裡已獲得相當程度的成功，並且吸引許多研究的投入。主動式有機發二極體展現了高度的潛力，也許在未來能成為主宰顯示器的元件。在它的每一個像素中，都包含了薄膜電晶體，而有機薄膜電晶體被應用於全彩顯示器是非常可能的一件事情，且有機薄膜電晶體有與生俱來N型特性。 由這個角度切入，底部是陰極的倒置元件結構比起傳統顯示器的結構，更適用於有機薄膜電晶體。雖然有機發光二極體具有某些優點，例如:反應時間短、高度的可撓性，但他也有一些缺點，像是較高的操作電壓、較短的壽命，這些是仍需要被改善的部分。在這篇論文中，我們使用熱蒸鍍的方式去長N型摻雜有機薄膜(MADN:Li2CO3)，並探討此薄膜作為電子注入層是如何改善元件表現。 目前此材料組合尚未被應用於倒置及正常之OLED元件，故為本研究動機之一部分。
首先，我們依序蒸鍍不同濃度的鹼金族碳化物，使其長在銦錫氧化物基板上，接著依序鍍上發光層、電子傳輸層、電子注入層，最後鍍上鋁作為陽極。我們主要觀察電子注入層帶給元件的改善以及探討他的機制。元件特性的量測可以用來了解電性及光學性質，X射線光電子能譜儀及紫外光電子能譜則用來探討元素的束縛能和公函數，原子力顯微鏡則應用在表面粗糙度和表面形貌的量測。由上述分析，我們可以了解到此N型摻雜薄膜的確在改善元件表現方面有卓越的效果。
接著，我們應用此N型摻雜薄膜於傳統的結構中，與倒置結構比較，試著在不同結構的元件表現中找出機制。最後，為了研究元件的可靠度和光學性質，我們進一步做了穿透度及壽命量測，結果指出此薄膜在兩種結構中皆有突出表現。

Organic-Light Emitting Diodes have been applied in small size displays and lots of efforts were dedicated in. Active matrix OLEDs show high potential for becoming the dominant technology in the future. Each pixel consists of a thin film transistor (TFT). Oxide TFTs, which have n type conductivity, are competitive candidates for achieving full color display. Therefore, inverted structure OLEDs with a bottom cathode are suitable for conventional displays. Although OLEDs have some advantages, such as fast response and high flexibility, there also have some drawbacks, such as high operation voltage and short lifetime, that need to be improved. In this thesis, we use thermal evaporation method to deposit MADN:Li2CO3 films as an n type buffer layer in OLEDs devices, and investigate how the buffer layers improve the device performance. To the author’s knowledge, MADN:Li2CO3 has not been previously used as a buffer layer for both inverted and normal OLEDs, which is the motivation for the present work.
Organic cathode buffer layers doped with various concentrations of alkali metal carbonate were deposited on indium tin oxide substrates. The emission, hole transport, hole injection layers and the anode were then deposited. We focus the results and mechanism on the improvements due to the electron injection layer. Current density-voltage-luminance measurements were conducted to evaluate the electro-optical properties. X-ray Photoelectron Spectroscopy and Ultraviolet Photoelectron Spectrometry were used to measure molecular binding energy and work function. Atomic Force Microscope was applied to measure the surface roughness and morphology. These measurements show that the MADN: Li2CO3 cathode buffer layer effectively improves the performance of OLED devices.
Then, the MAND:Li2CO3 buffer layer was applied to a normal OLED　structure. A performance comparison was made with the inverted structure. To investigate reliability and optical properties, transmittance and lifetime measurements were used. The results indicate that MADN:Li2CO3 is a novel buffer layer for both structures.

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