在1987，曾氏等人在柯達實驗室發現了有機材料的發光現象，由於材料的特性影響，我們可以製作出奈米級的發光二極體。在簡單的三明治結構中，一般我們使用NPB為電洞傳輸層，ALQ3為電子傳輸層及發光層。本文中，發現電壓巔峰值會隨厚度增加而增加，而所定義的崩潰電壓一樣會隨著厚度的增加而增加。在較薄的元件動作時，穿透電流為主導的電流，較厚的元件則為飄移電流所主導，另外，電流的數值會與介面的能障高低相關。除此以外，也發現了一個特殊的現象就是在ITO/NPB(40nm)/Al的元件中，會有低電流的產生，這部分的真正原因並不清楚，仍有待研究。除了上述因素外，外加電場也會影響元件的電特性，在ALQ3的部分，發現反向偏壓時候，會有電壓遞減的現象。但是在順向偏壓時，卻會隨著厚度增加而逐漸飽和。

Since Tang and Van Slyke reported efficient electroluminescence from a bilayer organic device in 1987, organic light emitting devices (OLEDs) have attracted great attention due to their potential toward the fabrication of large-area displays. To achieve efficient electroluminescence, OLEDs based on some molecules, in general, have separate layers of a hole transport material (HTM) and an emitting electron transport material (ETM). Naphtyl-substituted benzidine derivative (NPB) and tris (8-hydroxyquinoline) aluminum (AlQ3) are often been used as a HTM and an emitting ETM.

In this study, we try to deposit nano-scaled NPB and AlQ3 using a thermal evaporation system, separately. In simple sandwich structure, ITO/organic/Al, we try to investigate the electrical (I-V) characteristics of these organic thin films. The experimental results for NPB films show that the peak voltage (the voltage at which the current reaches its maximum values) increases with increasing the thickness of the organic films at forward bias. On the other hand, it also shows that the breakdown voltage (the voltage at which the current reaches zero value) increases with increasing the thickness as operating at reverse bias. As the thickness of the device is thin, the dominated current is the tunneling current. On other hand, as the thickness is thicker, the dominated current is the drift current. The current is influenced by the barrier of the interface energy. We found a peculiar image of low current in ITO/NPB (40 nm)/ Al device and we do not clear that the real cause. It should be studied for more research. On the other hand, the I-V characteristics of the devices will also be affected by the external electrical field.

As for the devices consisted of AlQ3, the electrical field decreases with increasing the thickness of the organic films at reversed bias and increases with increasing the thickness and finally saturates at forward bias.

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