Recombination in SnO2-Based Quantum Dots Sensitized Solar Cells: The Role of Surface States

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• 作者：Qingli Huang ; Fan Li ; Yun Gong ; Jianheng Luo ; Shize Yang ; Yanhong Luo ; Dongmei Li ; Xuedong Bai ; Qingbo Meng
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：May 30, 2013
• 年：2013
• 卷：117
• 期：21
• 页码：10965-10973
• 全文大小：522K
• 年卷期：v.117,no.21(May 30, 2013)
• ISSN：1932-7455

文摘

Tin oxide (SnO₂) is one of the most promising electron transporters to further enhance the performance of quantum dots sensitized solar cells (QDSCs). Unfortunately, the performance of SnO₂-based QDSCs is still poor. It was observed that surface modification toward a SnO₂ photoelectrode such as a TiCl₄ treatment is crucial to dramatically increase the performance of the devices. However, the mechanism of the TiCl₄ treatment remains poorly understood. Here, systematic studies on the photoelectrochemical properties of SnO₂-based QDSCs were performed in order to clarify the mechanism by which the TiCl₄ treatment improves the performance of solar cells. Impendence spectroscopy results reveal that the photogenerated electrons transport in the porous SnO₂ network rather than the TiO₂ coating. Furthermore, a physical model considering the existence of monoenergetic surface states at the SnO₂ surface was used to simulate the behavior of chemical capacitance at various forward biases. The accordance between the decrease of the surface states and the recombination reduction clearly indicates that the surface states act as the recombination centers to influence the device performance, which can be well described by Marcus-Gerischer theory. These combined findings provide new understanding of the recombination mechanism of SnO₂-based sensitized solar cells and guidelines for further improving the performance of this system.