聚(3-己烷基噻吩)摻雜祖母綠雙噻吩駢環芳香烴化合物薄膜性質與電性探討

Abstract

本文主要探討不同結構小分子，以不同比例摻雜入 P3HT，對載子遷移率 (mobility) 之影響。利用合成方式製備平面性結構雙噻吩駢環芳香烴化合物 emeraldicene (EMD)，及具有 2-ethylhexyl (EH) 烷基鏈與溴 (Br) 取代基的衍生物 2EH-EMD 與 2Br-2EH-EMD 作為摻雜小分子。另一方面，合成非平面性芳香烴化合物 2Th-An 來與上述小分子比較對於 P3HT 高分子鏈的影響。此一系列小分子以不同比例與 P3HT 混摻製備薄膜，利用薄膜電晶體 (thin film transistor, TFT) 元件來觀察載子遷移率增減的變化。並使用紫外光－可見光光譜與螢光光譜了解不同小分子添加物以不同比例製作 P3HT 薄膜，對 P3HT 吸收與放光產生的影響。除此之外，以光學顯微鏡觀察這一系列薄膜細微結構的變化或結晶狀況，與載子遷移率的關係。以 2Th-An 為例，在低混摻比例時，光學顯微鏡的表面型態與純 P3HT 幾乎相同，但 25 % 的 2Th-An 摻混比例，結晶尺寸變大且均勻分散，50 % 的結晶尺寸更大且分布變得密集；2EH-EMD在各混摻比例沒有明顯變化，結晶分布均勻，且尺寸均大於 P3HT；EMD 與 2Br-2EH-EMD 皆有明顯的黑色顆粒，在 P3HT 中產生聚集。在有機薄膜電晶體部分，2EH-EMD 與 2Th-An 皆可測得電晶體特性，載子遷移率約為10-4 - 10-2 cm2V-1s-1，其中 2Th-An (25 %) 為所有材料中表現最佳，具有 3.6×10-2 cm2V-1s-1 的載子遷移率，開關電流比為 1.8，起始電壓為 -10.1 V。

Several polycyclic heteroaromatic hydrocarbons with planar structures such as emeraldicene (EMD) and its derivatives 2EH-EMD, 2Br-2EH-EMD, and an aromatic compound with non-planar structure such as 2Th-An were synthesized and characterized. These four compounds were respectively used as additives to blend into P3HT with different weight ratios (1 wt%, 2 wt%, 5 wt%, 25 wt%, and 50 wt%) for organic thin film transistors (OTFTs). After spin-coating the thin films, we used the solvent treatment to enhance the ordered packing of the polymer chains. Photophysical properties were determined by UV-visible spectroscopy and photoluminescence. There were no changes on the absorption peak and the emission peak of P3HT after blending the small molecules into it. OM results indicate that for P3HT/ 2Th-An (25 wt%), P3HT/ 2Th-An (50 wt%) and all of P3HT/ 2EH-EMD samples, the domain sizes were larger than that in P3HT. For the P3HT/ EMD and P3HT/ 2Br-2EH-EMD samples, the aggregation of small molecules was observed. A series of organic thin film transistors based on the respective blends of P3HT and small molecules were fabricated. Electrical properties could be measured only for the P3HT/ 2EH-EMD and P3HT/ 2Th-An samples. The ranges of mobilities were about 10-4 to 10-2 cm2V-1s-1. The highest mobility (3.6×10-2 cm2V-1s-1), on/off ratio (1.8), and threshold voltage (-10.1 V) were observed for the P3HT/ 2Th-An (25 wt%) based organic thin film transistor.