一維P3HT奈米線與P3HT薄膜熱電性質量測與比較

Abstract

近年來的能源危機，世界上的科學家們正努力尋找替代能源，熱電也是其中之的替代能源一。在熱電領域中，一般來說半導體材料因為具有較好的熱電轉換效率(ZT值)，此材料為較被科學家所研究的，我們所選擇的材料P3HT其能隙約1.9 eV，介於半導體的能隙，期許期會有好的熱電轉換效率，再者P3HT為導電高分子材料其擁有好的電導率，而低維度可降低熱導值，好的電導率與越差的熱導率將會有助於提升ZT值，因此我們針對P3HT單根奈米線來探討其電性和熱導。 我們所使用「T-type」製程方法包含電漿輔助化學氣相沉積、電子束微影、金屬電極蒸鍍和濕式蝕刻來製作測量熱導率的基板，此製程方法較一般最常使用的「MEMS」簡單省時，且可使用直流電來測量，並使用公式推導求得熱導率。 實驗成功量到單根P3HT奈米線電導約為3.3x10-7(1/ohm)，並且針對奈米線的穩定度也做了測試，連續六日測得奈米線電導約在∓5%中，而熱導率為0.0552 (W/mK)。 也針對了P3HT奈米線與P3HT Film做了UV-VIS吸收光譜、XRD量測圖、熱導率、電導之比較。

In recent years, thermoelectric energy has become more popular due to the fact that we are constantly searching for new solutions to solve the looming energy crisis. To determine the heat conversion efficiency of a material, one must measure its figure of merit (ZT value). In general, a higher ZT value would mean greater efficiency of turning heat into electricity. Electrical conductivity, thermal conductivity and Seebeck coefficient are much related to ZT value. Among various thermoelectric materials, semiconductors are the most popular materials that are constantly studied due to their better ZT values. Recently, the conducting polymer, Poly(3-hexylthiophene) (P3HT), has been extensively studied because of its unique thermal and electrical properties. The band gap of P3HT is about 1.9 eV, which is in the same the band gap range of typical semiconductors. By making the P3HT into nanowires, we expects to lower the thermal conductivity of the nanowires due to the reduced dimensionality and to improve their ZT values. We successfully determined an electrical conductivity of 3.3x10-7 1/ohm from single P3HT nanowires. The value of the electrical conductivity remained stable even after wires were exposed in ambient for weeks. In addition, we fabricated “T-type” devices by using PECVD, E-beam lithography, E-gun evaporation and wet-etch to measure the thermal conductivity of single P3HT nanowires. We extracted a thermal conductivity of 0.0552 (W/mK) from a single P3HT nanowire.