Nanocrystal Size-Dependent Efficiency of Quantum Dot Sensitized Solar Cells in the Strongly Coupled CdSe Nanocrystals/TiO2 System

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• 作者：Hyeong Jin Yun ; Taejong Paik ; Benjamin Diroll ; Michael E. Edley ; Jason B. Baxter ; Christopher B. Murray
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：June 15, 2016
• 年：2016
• 卷：8
• 期：23
• 页码：14692-14700
• 全文大小：575K
• 年卷期：0
• ISSN：1944-8252

文摘

Light absorption and electron injection are important criteria determining solar energy conversion efficiency. In this research, monodisperse CdSe quantum dots (QDs) are synthesized with five different diameters, and the size-dependent solar energy conversion efficiency of CdSe quantum dot sensitized solar cell (QDSSCs) is investigated by employing the atomic inorganic ligand, S^2–. Absorbance measurements and transmission electron microscopy show that the diameters of the uniform CdSe QDs are 2.5, 3.2, 4.2, 6.4, and 7.8 nm. Larger CdSe QDs generate a larger amount of charge under the irradiation of long wavelength photons, as verified by the absorbance results and the measurements of the external quantum efficiencies. However, the smaller QDs exhibit faster electron injection kinetics from CdSe QDs to TiOb>2b> because of the high energy level of CBb>CdSeb>, as verified by time-resolved photoluminescence and internal quantum efficiency results. Importantly, the S^2– ligand significantly enhances the electronic coupling between the CdSe QDs and TiOb>2b>, yielding an enhancement of the charge transfer rate at the interfacial region. As a result, the S^2– ligand helps improve the new size-dependent solar energy conversion efficiency, showing best performance with 4.2-nm CdSe QDs, whereas conventional ligand, mercaptopropionic acid, does not show any differences in efficiency according to the size of the CdSe QDs. The findings reported herein suggest that the atomic inorganic ligand reinforces the influence of quantum confinement on the solar energy conversion efficiency of QDSSCs.