具有奈米金屬網之液態製程有機顯示器( I )

Abstract

本計畫有兩個主要大方向。第一，我們研發多年的空間電荷限制電晶體(Space-Charge-Limited Transistor，SCLT )，成為第一個被廣泛應用的液態製程電晶體，我們將藉由基礎科學研究進一步提升電晶體效能及製程可靠度。第二，藉由產學合作關係與永豐餘集團 元太科技(E Ink Holdings)共同開發大面積主動式矩陣有機發光二極體顯示器(Active-Matrix Organic Light-Emitting Diode Display，AMOLED)，其中有機發光二極體(Organic Light-Emitting Diode，OLED)與SCLT的大面積刮刀塗佈方式皆由本團隊所發展。SCLT是固態真空三極管的概念，相同之處都是以基極金屬來調變射極與集極間的位能障，進而控制載子能否在射極、集極間傳輸。我們垂直式電晶體的概念最早發展於2006年，目的是期望藉由垂直式電晶體中較短的傳輸通道，改善有機半導體材料應用在一般場效電晶體，因低載子遷移率及較長的傳輸通道導致的高操作偏壓與低輸出電流等缺點。於現今SCLT結構中通道長度僅300 nm遠小於場效電晶體，這也是目前我們發展的SCLT在整體效能上優於一般液態製程的場效電晶體的原因。 在計畫提案中的教授都是長期合作夥伴及共同發表許多文獻。在子計畫一，孟心飛和王倫教授針對同樣使用刮刀塗佈方式的SCLT與OLED作整合。王倫是雷射干涉微影和奈米壓印領域專家，將其運用在SCLT金屬奈米網結構上研發較可靠方式來製作規則化SCLT基極電極，降低隨機奈米孔洞網缺陷造成的漏電。子計畫二中，冉曉雯與趙昌博教授將進一步提升電晶體效能，如輸出電流密度、電流開關比及操作電壓，都牽扯到基礎元件物理及新穎製程科技，尤其是垂直通道側壁化學處理影響了分子排列與載子傳輸為主要關鍵。單一AMOLED畫素需2-4個不同需求的電晶體，這包含到畫素電路設計、模擬和展示。子計畫三中，陶雨台教授將延伸成果把半導體材料改成結晶、液晶或非結晶小分子材料，並探討分子堆疊在受限的垂直通道中之排列控制，進一步將自主緊密排列的奈米球當作蒸鍍遮罩作規則化基極金屬網，改善缺陷造成的漏電。此計畫包含了各領域人才，基於過去的成功合作及各項技術，相信我們能夠達成目標。

There are two main goals in this project. First by basic study we plan to raise the performance and fabrication reliability of the vertical space-charge-limited transistor (SCLT), under development by us for several years, such that it becomes the first solution-processed transistor to be widely applied. Second we will collaborate with E Ink Holdings to develop large-area active-matrix organic light-emitting diode display (AMOLED) technology, in which both the OLED and the SCLT are fabricated by blade coating in large area also developed by us. SCLT is basically a solid-state version of vacuum tube triode. Both of them have a grid metal electrode to modulate the potential profile between the carrier emitter and collector. The exploration of new concepts on vertical organic transistor started in our group started back in 2006 in the hope to realize high-performance solution-processed transistor given the intrinsically low carrier mobility. The basic idea is to replace the long horizontal channel in conventional field-effect transistor by the short vertical channel defined by the semiconductor film thickness. Currently the SCLT is superior to the conventional solution-processed field-effect transistor in terms of overall performance. The professors in this proposal already have long collaboration in both SCLT and other organic semiconductor devices with many joint publications. In the first sub-project by HF Meng and L Wang we will study how to integrate SCLT and OLED in the same blade coating platform. L Wang is an expert in laser interference lithography and nano-imprint. Recently these methods are first applied in a working SCLT. We will follow this initial step and develop a reliable method to fabricate SCLT base electrode with regular grid for low off-current. In the second sub-project by HW Zan and CP Chao we will further raise the performance parameters like output current density, on-off ratio, and range of operation voltage. These works involve the fundamental understanding of the device physics and novel process techniques. In particular, the chemical treatment of the vertical side wall is a key approach to control the molecular morphology and the carrier transport. In a single AMOLED pixel there are 2-4 transistors with different requirements. The pixel circuit design, simulation, and demonstration will be carried out in this sub-project. In sub-project 3 by YT Tao we will extend our previous works using polymer semiconductors into crystalline, liquid-crystalline, or amorphous small molecules. The control of the molecular stacking in such confined vertical nano-channel is a challenging and interesting scientific problem. In general the π-stacking of the organic semiconductor molecules need to be aligned vertically in order to have a high mobility. In this project we will also further develop the fabrication method for the regular grid base by the self-assembled close-packed plastic spheres as the template. Such method has been demonstrated for SCLT recently. Similar to the case of laser interference lithography in sub-project 1, the regular grid is free of the problem of inevitable large channels and has potentially lower off-current than in the case of random grid made by the random plastic sphere array.