Abstract
二、以溶劑熱法合成閃鋅礦和纖維鋅礦之硫化銅銦奈米晶體及其太陽能電池的應用 具有相當潛力的銅銦硫太陽能電池是由三個元素(I-III-VI2)所組成的半導體，可作為薄膜太陽能電池中的吸收層材料。目前銅銦硫太陽能電池已經被證實了具有20%的太陽能轉換效率。大部分所合成出銅銦硫的奈米晶體結構為黃銅礦(chalcopyrite)，然而在2008年，Pan的研究團隊利用熱注射法第一次成功地合成出閃鋅礦(zinc blende)以及纖維鋅礦(wurtzite)的銅銦硫奈米晶體。 本論文則是在溫度160℃下，以氯化銅(CuCl2)、氯化銦(InCl3)、硫代硫醯胺(thioacetamide，C2H5NS)、十八油胺(oleylamine，C18H37N)、以及乙二胺(ethylenediamine，C2H8N2)為反應物。僅藉由調控十八油胺以及乙二胺加入的比例則可以合成出閃鋅礦(zinc blende)以及纖維鋅礦(wurtzite)的銅銦硫奈米晶體。粉末X光繞射儀和穿透式電子顯微鏡的鑑定可以很明確地觀測到銅銦硫奈米結構的相轉換。在紫外光可見光吸收光譜中，可以發現所合成的銅銦硫產物皆於可見光到近紅外光區擁有強烈的全區吸收。在此我們也利用此特性將銅銦硫奈米粒子製成太陽能電池的吸收薄膜層，證實了合成出的銅銦硫奈米晶體確實能應用於太陽能電池。 A promising thin film photovoltaic technology is CIS-based solar cells, which are based on the use of ternary I-III-VI2 semiconductors as photovoltaic absorber material. CIS solar cells have already demonstrated nearly 20% solar energy conversion efficiency. CuInS2 nanostructures with mostly a chalcopyrite crystal structure have been prepared. In 2008, by using a hot-injection method, Pan et al. prepared zinc blende and wurtzite CuInS2 nanocrystals for the first time. Here, we have synthesized CuInS2 nanocrystals by a simple one-step solvothermal method at 160 ºC for 12 h. Copper chloride (CuCl2), indium chloride (InCl3), thioacetamide (TAA), ethylenediamine and oleylamine were used as the reagents. By adjusting the volume of oleylamine and ethylenediamine used while keeping the other experimental conditions constant, the phase transition of CuInS2 nanostructures from zinc blende (cubic) to wurtzite (hexagonal) structure can be achieved. The crystal phases were confirmed by powder X-ray diffraction and selected-area electron diffraction techniques. The CuInS2 products show strong light absorption from the entire visible to the near-IR region. This characteristic suggests their possible integration into solar cells with enhanced solar energy conversion efficiency.