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Electrolyte-dependent photovoltaic responses in dye-sensitized solar cells based on an osmium(II) dye of mixed denticity

Journal of Physical Chemistry C, ISSN: 1932-7447, Vol: 114, Issue: 14, Page: 6831-6840
2010
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Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    26
    • Citation Indexes
      26
  • Captures
    48

Article Description

This work focuses upon the effects of electrolyte composition, specifically the role of Li and I ions, on the resultant photovoltaic performance of dye-sensitized solar cells (DSCs) based on a new Os(II) polypyridine complex of mixed denticity, [Os(Bu tpy)(dcbpyH)(NCS)]PF (1). Photophysical and electrochemical characterization of 1 confirmed the suitability of this dye to serve as a sensitizer for regenerative DSCs on mesoscopic titania films. Device photovoltaic performances were assessed by measuring external quantum efficiencies as a function of wavelength, and current-voltage curves, the latter under simulated AM1.5G one-sun illumination. Varying the concentration of LiI in the redox electrolyte affects the short-circuit photocurrent (J ), open-circuit voltage (V), fill factor (ff), power conversion efficiency (η), and external quantum efficiency (EQE) of the individual devices. Increasing the concentration of LiI results in enormous increases in J in the Os(II)-based devices accompanied by corresponding decreases in V. Independently increasing the concentration of I by using either tetrabutylammonium iodide (TBAI) or the ionic liquid 1-n-propyl-3-methylimidazolium iodide (PMII) was found to increase J without concomitantly lowering the V. These observations are discussed and directly compared in parallel to devices based on the benchmark sensitizer N3, cis-Ru(dcbpyH)(NCS) . The combined results suggest that the photovoltaic performance of Os(II)-based DSCs can indeed be optimized by simply modifying the composition of redox electrolytes used in the operational sandwich cells. An abundance of I appears to be crucial for the effective regeneration of oxidized surface-bound osmium sensitizers and therefore for the production of higher photocurrents in these devices. We note that select devices based on 1 represent the record power conversion efficiency for an Os(II)-based DSC measured under simulated AM1.5G one-sun illumination, η = 4.7%. © 2010 American Chemical Society.

Bibliographic Details

Anthony C. Onicha; Felix N. Castellano

American Chemical Society (ACS)

Materials Science; Energy; Chemistry

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