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Geminate charge recombination in alternating polyfluorene copolymer/fullerene blends
Swati De1, Torbjörn Pascher, Manisankar Maiti
1Chemical Physics, Lund University, PO Box 124, SE-22100 Lund, Sweden.
Journal of the American Chemical Society
|June 15, 2007
Summary
In polymer/fullerene solar cells, fast geminate recombination dominates charge decay at low light intensities, potentially hindering efficient charge collection under solar illumination.
Area of Science:
- Organic electronics
- Photovoltaic materials science
Background:
- Polymer/fullerene blends are key materials for organic solar cells.
- Understanding charge dynamics is crucial for improving device efficiency.
Purpose of the Study:
- To investigate excited state and charge dynamics in polyfluorene copolymer/fullerene derivative blends.
- To determine the dominant charge decay mechanisms under solar cell relevant conditions.
Main Methods:
- Time-resolved spectroscopy was used to monitor processes over nine orders in time.
- Measurements were conducted across two orders of light intensity.
Main Results:
- Ultrafast charge photogeneration and slower charge recombination were observed.
- Geminate recombination (approx. 30 ns) was the primary decay pathway at low light intensities.
- Nongeminate recombination contribution was found to be negligible.
Conclusions:
- Geminate recombination significantly impacts charge dynamics in these systems.
- This fast geminate recombination may compete with charge collection in polymer/fullerene solar cells under operational conditions.
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