Role of adsorption structures of Zn-porphyrin on TiO2 in dye-sensitized solar cells studied by sum frequency generation vibrational spectroscopy and ultrafast spectroscopy

Shen Ye, Arunkumar Kathiravan, Hironobu Hayashi, Yujin Tong, Yingyot Infahsaeng, Pavel Chabera, Torbjörn Pascher, Arkady P. Yartsev, Seiji Isoda, Hiroshi Imahori, Villy Sundström

研究成果: Article査読

130 被引用数 (Scopus)

抄録

Several Zn-porphyrin (ZnP) derivatives were designed to build highly efficient dye-sensitized solar cells (DSC). It was found that solar cell efficiencies normalized for surface coverage (ηrel) are affected by the molecular spacer connecting the porphyrin core to the TiO2 surface, the sensitization conditions (solvent and time), and, to a lesser extent, the nature of the terminal group of the ZnP. Ultrafast transient absorption spectroscopy shows that electron transfer rates are strongly dependent on spacer and sensitization conditions. To understand this behavior at a molecular level, surface-sensitive vibrational spectroscopy, sum frequency generation (SFG), has been employed to investigate the adsorption geometries of these ZnP derivatives on the TiO2 surface for the first time. The average tilt angles and adsorption ordering of the ZnP molecules on the TiO 2 surface were measured. A simple linear correlation between adsorption geometry of the adsorbed ZnP molecules, ηrel, and the concentration of long-lived electrons in the conduction band of TiO2 was shown to exist. The more perpendicular the orientation of the adsorbed ZnP (relative to the TiO2 surface), the higher the concentration of long-lived electrons in the conduction band, which contributes to the increase of photocurrent and solar cell efficiency. This result indicates that the electron transfer between ZnP and TiO2 occurs "through- space" rather than "through the molecular spacer". It is also revealed that the sensitization solvent (methanol) may affect adsorption geometry and adsorption ordering through coadsorption and modify the electron transfer dynamics and consequently solar cell efficiency. Aggregation effects, which were observed for the longer sensitization times, are also discussed in relation to adsorption geometry and radiationless quenching processes. With the work reported here we demonstrate a novel strategy for DSC material characterization that can lead to design and manufacturing of photoactive materials with predictable and controlled properties.

本文言語English
ページ(範囲)6066-6080
ページ数15
ジャーナルJournal of Physical Chemistry C
117
12
DOI
出版ステータスPublished - 2013 3 28
外部発表はい

ASJC Scopus subject areas

  • 電子材料、光学材料、および磁性材料
  • エネルギー(全般)
  • 物理化学および理論化学
  • 表面、皮膜および薄膜

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