Fabrication of Poly(3-hexylthiophene) Nanowires and Effect of Thermal and Solvent Annealing
|關鍵字:||聚三己基噻吩;奈米線;晶鬚法;退火處理;共軛高分子太陽能電池;有機場效電晶體;Poly(3-hexylthiophene);Nanowires;Whisker method;Annealing;Conjugated polymer solar cell, .;Organic field effect transistor|
|摘要:||聚三己基噻吩(Poly(3-hexylthiophene), P3HT)是一個近幾年相當熱門的共軛高分子材料，主要是其具有獨特的物理與電學特性，因此被廣泛應用於有機光電元件，例如共軛高分子太陽能電池(conjugated polymer solar cells, CPSC)、有機場效電晶體(organic field effect transistor, OFET)或是有機發光二極體(organic light-emitting diodes, OLED)等。
本篇論文是利用晶鬚法(whisker method)與混和溶劑法(mix-solvent method)來製備聚三己基噻吩的奈米線，並探討溫度退火與溶劑退火對聚三己基噻吩奈米線的形態與結晶性等特性的影響。晶鬚法主要是將聚三己基噻吩利用加熱的方式使其溶解於臨界溶劑中，在高分子溶液降溫的過程中，因高分子與臨界溶劑間的作用力，使高分子鏈自組裝為線狀的奈米結構，經原子力顯微鏡(atomic force microscope, AFM)與穿透式電子顯微鏡(transmission electron microscope, TEM)檢視下，發現聚三己基噻吩奈米線長度為微米等級，寬度約為二十到三十奈米，是具有相當大長寬比的奈米結構。聚三己基噻吩奈米線經溫度退火與溶劑退火後並無發現雷利不穩定性之類的形態轉變，其形態仍可保持。經X光繞射儀(X-Ray Diffraction, XRD)與示差掃描量熱分析儀(Differential Scanning Calorimetry, DSC)鑑定後，發現聚三己基噻吩奈米線的結晶性獲得提升。接著我們將此結果應用於反式共軛高分子太陽能電池與有機場效電晶體，發現載子遷移率了提升一個數量級，而光電轉換效率提升了近70 %。|
In recent years, poly(3-hexylthiophene) (P3HT) has been extensively studied because of its unique physical and electrical properties. P3HT-based materials has been widely applied to different optoelectronic devices such as s conjugated polymer solar cell (CPSC), organic field effect transistor (OFET), and organic light-emitting diode (OLED). In this thesis, we prepared P3HT nanowires by using the whisker method and the mix-solvent method. We also studied the effects of thermal annealing and solvent annealing on the morphologies and crystallinities of P3HT nanowires. In the whisker method, P3HT is dissolved in heated p-xylene which is a marginal solvent for P3HT at room temperatures. After cooling, P3HT nanowires are formed by self-assembly and are dispersed in p-xylene. The formation of the nanowires was confirmed by atomic force microscope (AFM) and transmission electron microscope (TEM). The lengths of the nanowires with high aspect ratios are several microns and the diameters are about 20-30 nm. After thermal and solvent annealing, the morphologies of P3HT nanowires are maintained, and the Rayleigh-instability-type transformation of the P3HT nanowires is not observed. The crystallinities of the P3HT nanowires were found to be increased, as confirmed by X-Ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC). The device performances of organic field effect transistors and organic solar cells were also examined. The charge mobility is increased by one order, and the power conversion efficiency is increased by ~ 70 %.