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Correlation of Absorption Profile and Fill Factor in Organic Solar Cells: The Role of Mobility Imbalance
Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology. Technical University of Dresden, Germany .
Technical University of Dresden, Germany .
Technical University of Dresden, Germany .
Technical University of Dresden, Germany .
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2013 (English)In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 3, no 5, 631-638 p.Article in journal (Refereed) Published
Abstract [en]

We investigate the role of the spatial absorption profile within bulk heterojunction small molecule solar cells comprising a 50 nm ZnPc:C60 active layer. Exploiting interference effects the absorption profile is varied by both the illumination wavelength and the thickness of an optical spacer layer adjacent to the reflecting electrode. The fill factor under 1 sun illumination is observed to change from 43 to 49% depending on the absorption profile which approximately equals the charge-carrier generation profile. It is shown by varying the mixing ratio between ZnPc and C60 that the importance of the generation profile is correlated with the imbalance of mobilities. Therefore, it is concluded that non-geminate recombination is the dominating loss mechanism in these devices. Numerical drift-diffusion simulations reproduce the experimental observations showing that charge carrier extraction is more efficient if charge carriers are generated close to the contact collecting the less mobile charge carrier type. Furthermore, this effect can explain the dependence of the internal quantum efficiency measured at short circuit on wavelength and implies that the spectral mismatch for a given solar simulator and device depends on the applied voltage.

Place, publisher, year, edition, pages
Wiley-VCH Verlag , 2013. Vol. 3, no 5, 631-638 p.
Keyword [en]
recombination, quantum efficiency, spectral mismatch, imbalanced mobilities, generation profile, zinc-phthalocyanine, C60, bulk heterojunction, organic solar cell, fill factor
National Category
Social Sciences
URN: urn:nbn:se:liu:diva-94323DOI: 10.1002/aenm.201200835ISI: 000318761500012OAI: diva2:631990

Funding Agencies|Bundesministerium fur Bildung und Forschung|13N9720|InnoProfile project|03IP602|Reiner Lemoine foundation||

Available from: 2013-06-24 Created: 2013-06-24 Last updated: 2013-06-24

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Tress, Wolfgang
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Biomolecular and Organic ElectronicsThe Institute of Technology
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