Imbalanced mobilities causing S-shaped IV curves in planar heterojunction organic solar cells

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We show that S-kinks in the current voltage characteristics, which decrease the fill factor significantly, can be caused by a strong imbalance of charge carrier mobilities (hole mobility in donor and electron mobility in acceptor) in planar/flat heterojunction organic solar cells. Electrical simulations according to a drift-diffusion model predict the occurrence of an S-kink for a mobility mismatch factor larger than 100. By combining a low-mobility donor material, (1,2,3,4,9,10,11,12-octaphenyl-diindeno[1,2,3-cd:1′,2′,3′-lm]perylene), with the acceptors C60 and N,N′-dimethylperylene-3,4:9,10-dicarboximide, which show different electron mobilities, we experimentally verify the predictions. Our results demonstrate that not only interface effects but also the photoactive material itself can cause S-kinks.W.T. thanks the Reiner Lemoine Foundation for funding. Additional support from BMBF (OPEG Grant No. 13N9720 and Innoprofile Grant No. 03IP602) is gratefully acknowledged.


Original languageEnglish
Article number063301
Number of pages3
JournalApplied physics letters
Issue number6
Publication statusPublished - 7 Feb 2011

External IDs

Scopus 79951777825


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