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Journal article

Tracking the adsorption and electron injection rates of CdSe quantum dots on TiO2: Linked versus direct attachment

Pernik D, Tvrdy K, Radich J, Kamat P ...see all

Journal of Physical Chemistry C, vol. 115, issue 27 (2011) pp. 13511-13519

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Abstract

Understanding CdSe quantum dot (QD) adsorption phenomena on mesoscopic TiO2 films is important for improving the performance of quantum dot sensitized solar cells (QDSSCs). A kinetic adsorption model has been developed to elucidate both Langmuir-like sub-monolayer adsorption and QD aggregation processes. Removal of surface-bound trioctylphosphine oxide as well as use of 3-mercaptopropionic acid (MPA) as a mol. linker improved the adsorption of toluene-suspended QDs on TiO2 films. The adsorption const. Kad for sub-monolayer coverage was (6.7 ± 2.7) × 103 M-1 for direct adsorption and (5.9 ± 2.0) × 104 M-1 for MPA-linked assemblies. Prolonged exposure of a TiO2 film to a CdSe QD suspension resulted in the assembly of aggregated particles regardless of the method of adsorption. A greater coverage of TiO2 was achieved with smaller QDs due to reduced size constraints. Ultrafast transient absorption spectroscopy demonstrated faster electron injection into TiO2 from directly adsorbed QDs (kET = 7.2 × 109 s-1) compared to MPA-linked QDs (kET = 2.3 × 109 s-1). The adsorption kinetic details presented in this study are useful for controlling CdSe QD adsorption on TiO2 and designing efficient photoanodes for QDSSCs. [on SciFinder(R)]

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Authors

  • Douglas R. Pernik

  • Kevin Tvrdy

  • James G. Radich

  • Prashant V. Kamat

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