在環保意識的抬頭下，綠能科技成為現今各企業的開發重點，以及許多研究學者的研究重心。量子點敏化太陽能電池 (Quantum Dots Sensitized Solar Cells, QDSSC) 由於理論效率高，更是目前當紅的議題。然而目前文獻上所發表的QDSSC普遍使用鎘元素 (Cd) 以及鉛元素 (Pb) 的光敏化物，容易對我們的身體以及自然環境造成負面的影響，並非真正的綠能科技。因此在本研究中，選擇以低毒性的CuInS2量子點作為光敏化物，利用Oleic acid以及3-mercaptopropionic acid改質量子點的疏水性，獲得高穩定度的水溶性CuInS2量子點，此時組裝成CuInS2 QDSSC可獲得0.64%的光電轉換效率，相較於目前文獻上預先合成方法組裝的CuInS2 QDSSC，具有倍數的成長。接著再透過結合連續離子層吸附反應法 (Successive ionic-layer adsorption and reaction) 沉積CuInS2量子點於TiO2光電極上，增加光敏物的吸附量，並且達到共敏化的效果。另一方面，我們以簡易的製程即可獲得高表面積的Cu2S背電極，最後所封裝完成的CuInS2 QDSSC光電轉換效率可達1.84%的最佳效率。

A cadmium metal-free CuInS2 quantum dot (QD)-sensitized solar cell (QDSSC) has been fabricated by taking advantages of the ex-situ synthesized approach with high crystalline of QDs and in-situ successive ionic-layer adsorption and reaction process (SILAR) approach with high surface coverage of QDs. The ex-situ synthesized CuInS2 QDs can be rendered water-soluble through simplicity and rapidity two-step method under the assistance of ultrasonication. This approach allows a stepwise ligand change from the foreign ligand insertion to ligand replacement, which preserves long-term stability of colloidal solution more than one month. Furthermore, the resulting QDs can be exploited as sensitizer in QDSSC delivered a power conversion efficiency (PCE) of 0.64%. Following by using the SILAR process, the in-situ CuInS2 could be epitaxial growing on the pre-existing seeds of ex-situ synthesized CuInS2 QDs. The results indicated that the CuInS2 QDSSC fabricated by the combined ex-situ/in-situ growth exhibited PCE of 1.84% (Jsc = 7.72 mA/cm2, Voc = 570 mV, and FF = 41.8%), which is higher than those of CuInS2 QDSSC formed by ex-situ and in-situ growth, respectively. The photon-to-current conversion efficiency and electrochemical impedance spectroscopy have been carried out to substantiate photovoltaic behavior and the charge-transfer resistance. The results suggest that the combined synergetic effects of in-situ and ex-situ CuInS2 QD growth facilitating higher electron-injecting efficiency from the QD sensitizers into the TiO2.

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