Investigation of Charge Transfer in Ag/N719/TiO2 Interface by Surface-Enhanced Raman Spectroscopy

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• 作者：Xiaolei Wang ; Yue Wang ; Huimin Sui ; Xiaolei Zhang ; Hongyang Su ; Weina Cheng ; Xiao Xia Han ; Bing Zhao
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：June 23, 2016
• 年：2016
• 卷：120
• 期：24
• 页码：13078-13086
• 全文大小：508K
• 年卷期：0
• ISSN：1932-7455

文摘

The interfaces of metal–dye molecule–semiconductor sandwich structure are very important in the investigation of dye-sensitized solar cells (DSSCs) where metals are used to enhance absorption. In this work, we first designed and synthesized Ag/N719 and Ag/N719/TiO₂ sandwich systems to investigate the chemical binding type at the interfaces of Ag/N719/TiO₂. The results of the Raman spectra under the laser excitations of 532, 633, and 785 nm clarified that the SCN groups adsorbed on the Ag surface via the S terminal and the TiO₂ layer possibly bound to Ag/N719 via the ester linkage (—O—C═O) of the COOH group in N719. Then, we optimized the Ag substrate as an SERS detection platform and selected the Ag sol film as the substrate. Last, the relationship between the “degree of CT (ρ_CT)” in the SERS spectra and the charge transfer (CT) process was investigated by tuning the contribution from the chemical effect. We found that, owing to the introduction of TiO₂, the intensity and ρ_CT first increased (n = 0–2) and then decreased (n = 2–3) with the increase of the number of TiO₂ layers under 532 and 633 nm laser excitations. However, the intensity decreased (n = 0–3) with the increase of the number of TiO₂ layers under the laser excitation of 785 nm, and there was no obvious change about ρ_CT. Meanwhile ρ_CT became higher with the increase of the laser excitation energy at the interfaces with the same TiO₂ layer number. In order to explain these variations about ρ_CT, we utilize ultraviolet photoelectron spectroscopy (UPS) and UV–vis spectra to calculate energy levels for better understanding the charge transfer (CT) process, and the calculation result is in accordance with the variation tendency of ρ_CT.