Studies of Thin Film Structure and Charge Transport Properties of Regioregular Poly(3-hexylthiophene) and Its Blends

• Main Authors: Ming-Feng Jang, 張明峯
• Other Authors: Horng-Long Cheng
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/98797706503171373379

碩士 === 國立成功大學 === 光電科學與工程研究所 === 94 === 　　In this study, electronic transport properties of regioregular poly(hexylthiophene) (RR-P3HT) based organic thin-film transistors (OTFTs) were investigated. In part 1, the correlation between thin-film structure and carrier transport properties were investigated using RR-P3HT blending poly (methyl methacrylate) (PMMA) as an active layer in OTFTs. In the second part, bias-stress induced electronic characteristics variation of RR-P3HT-based OTFTs and structural changes of RR-P3HT active layer were studied. 　　Part 1: The RR-P3HT/PMMA blend films with different weight fractions were fabricated and their characteristics were analyzed using X-ray diffraction (XRD), absorption spectroscopy, and Raman spectroscopy. Structural analysis revealed that blending of PMMA reduced interchain interaction and efficient conjugation length of RR-P3HT, interrupted RR-P3HT to form lamellar microstructures, and increased the RR-P3HT chain disorder. Analysis of electric characteristics suggests that poor performance of the neat RR-P3HT OTFTs in air occurs due to the humidity and oxygen in air ambient, consequently limiting the formation of ideal field-effect channel. The phenomenon was improved by blending the PMMA into the RR-P3HT and thus inducing a sharper field-effect channel. However, we observed inferior field-effect mobilities in RR-P3HT/PMMA blends due to the dilute effect and inferior structure of RR-P3HT. 　　Part 2: The long-term electronic stability of RR-P3HT-based OTFTs were studied and the corresponding thin-film structure of RR-P3HT were also analyzed using XRD, absorption spectroscopy, and polarized Raman spectroscopy. After long-term bias stress, we have not found significant degradation in the field-effect mobility of RR-P3HT-based OTFTs in vacuum environment. However, the bias stress induced a decreasing output on-current, while threshold voltage shifted towards negative. The process was found to be partially irreversible. Structural analysis showed that the interchain interaction of RR-P3HT could be enhanced after long-term bias stress, thus resulting in occurrence of slight structural anisotropy, especially in the direction parallel to source-to-drain field.