Free Carrier Generation in Fullerene Acceptors and Its Effect on Polymer Photovoltaics
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AbstractEarly research on C60 led to the discovery that the absorption of photons with energy greater than 2.35 eV by bulk C60 produces free charge carriers at room temperature. We find that not only is this also true for many of the soluble fullerene derivatives commonly used in organic photovoltaics, but also that the presence of these free carriers has significant implications for the modeling, characterization, and performance of devices made with these materials. We demonstrate that the discrepancy between absorption and quantum efficiency spectra in P3HT:PCBM is due to recombination of such free carriers in large PCBM domains before they can be separated at a donor/acceptor interface. Since most theories assume that all free charges result from the separation of excitons at a donor/acceptor interface, the presence of free carrier generation in fullerenes can have a significant impact on the interpretation of data generated by numerous field-dependent techniques. © 2012 American Chemical Society.
CitationBurkhard GF, Hoke ET, Beiley ZM, McGehee MD (2012) Free Carrier Generation in Fullerene Acceptors and Its Effect on Polymer Photovoltaics. The Journal of Physical Chemistry C 116: 26674–26678. Available: http://dx.doi.org/10.1021/jp310821f.
SponsorsThis work was supported by the Center for Advanced Molecular Photovoltaics (Award KUS-C1-015-21), made by King Abdullah University of Science and Technology (KAUST). E.T.H. was supported by the National Science Foundation GRFP and the Fannie and John Hertz Foundation. We thank Rodrigo Noriega and Alberto Salleo for help with the PDS measurements and Koen Vandewal for his insights.
PublisherAmerican Chemical Society (ACS)