以奈米球模板技術製備透明導電電極之光性與電性研究

Abstract

透明導電電極是光電元件中最重要且最基礎的元件之ㄧ，銦錫氧化物(ITO)則是目前最廣為大家使用的透明電極材料。但構成銦錫氧化物中的重要元素「銦」有許多的迫切的問題，一是銦的蘊藏量在地球上極為有限，二則是伴隨著低蘊藏量隨之而來銦錫氧化物的高價格問題，自2003年至今，銦錫氧化物的價格已經高漲了十倍之多。因此尋求銦錫氧化物的透明電極替代品就成為眼前極為迫切的問題。 在此篇論文中，我們使用奈米模板技術和高真空熱退火製備了一系列高導電度與高穿透度的導電薄膜。在此類奈米結構設計中，穿透度與導電度是兩難的取捨權衡，在薄膜上挖出越高比例的金屬材料，將導致電性的急速下降，反之若是留下越多的金屬成分，則是無法兼顧到電極的光穿透度。在我們最佳化的設計(厚度10奈米，週期590奈米和54.69−58.341%填充率)中，能夠同時達到八成以上的穿透度與片電阻的35Ω/□。在討論完透明電極的的光電特性後，我們挑選了一適當的結構(厚度20奈米，週期590奈米和32.154%填充率)撘配上表面平坦化技術作為測試的透明導電電極，完成一綠光的有機發光二極體，使得元件起始電壓較傳統ITO元件下降0.4V，而電流效率更是增加了84%。

Transparent conductive electrode is one of the most important and basic components of the optoelectronics. Indium tin oxide (ITO) has been the most widely employed to fabricate the transparent electrode. But Indium metal itself that is the ingredient that comprises the largest portion in the ITO raw material has problems including extremely limited quantity, high price and unstable supply and demand. So ITO alternatives have become the subject of intense investigation for applications as transparent electrodes in optoelectronic devices. In this work, we used the nanosphere lithography and annealing process to create the patterned Ag thin film to achieve high transparency and conductivity. The optimization between transparency and conductivity is always a trade-off. Our optimized cases (10-nm-thick silver, 590-nm period, and 54.69−58.341% filling factor*) allow for a transparency of 80−85% and a sheet resistance lower than 35Ω/□. Using the patterned Ag thin film as the anode (20-nm thick, 590-nm period, and 32.154% filling factor) coated with SAM (Self-Assembly Monolayer), we successfully fabricated Alq3-based OLED devices. Compared with traditional ITO-based devices, the patterned Ag anode had a turn-on voltage decreased by 0.4V, and the current efficiency was increased by 84%.