Fast Low-Spin Cobalt Complex Redox Shuttles for Dye-Sensitized Solar Cells
1Department of Chemistry, Michigan State University, East Lansing, Michigan 48823-1322, United States.
The Journal of Physical Chemistry Letters
|August 19, 2015
Summary
Cobalt bis(trithiacyclononane) shows promise as a stable redox shuttle for dye-sensitized solar cells (DSSCs). Optimizations reduced recombination, improving performance and demonstrating potential for efficient regeneration.
Area of Science:
- Materials Science
- Electrochemistry
- Renewable Energy
Background:
- Dye-sensitized solar cells (DSSCs) require efficient redox shuttles for charge transport.
- Cobalt complexes offer potential as alternatives to traditional iodide/triiodide systems.
- Cobalt bis(trithiacyclononane), [Co(ttcn)2](3+/2+), is a novel low-spin cobalt(II) complex.
Purpose of the Study:
- To investigate the potential of [Co(ttcn)2](3+/2+) as a redox shuttle in DSSCs.
- To identify and mitigate performance limitations, particularly recombination.
- To compare its performance against established cobalt tris-bipyridine redox shuttles.
Main Methods:
- Synthesis of [Co(ttcn)2](3+/2+) from commercial ligands.
- Fabrication of DSSC photoanodes using nanoparticle-based TiO2.
- Variation of sensitizers and application of ultrathin alumina coatings.
- Photovoltaic performance testing and quantum yield measurements.
Main Results:
- [Co(ttcn)2](3+/2+) exhibits stability, transparency, and favorable energetic/kinetic properties.
- Recombination was identified as a key limitation in initial DSSC devices.
- Alumina coating and sensitizer modification significantly reduced recombination and improved quantum yields.
- DSSCs with [Co(ttcn)2](3+/2+) achieved over 2% efficiency with fast regeneration.
Conclusions:
- [Co(ttcn)2](3+/2+) is a viable and promising redox shuttle for DSSCs.
- Strategies to reduce recombination are crucial for enhancing DSSC performance.
- The complex demonstrates comparable performance to [Co(bpy)3](3+/2+) and enables efficient regeneration.
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