Regensburg 2010 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 17: Organic Semiconductors: Solar Cells I (Joint Session with DS/CPP/O)
HL 17.5: Talk
Monday, March 22, 2010, 17:00–17:15, H15
Relation of open circuit voltage to charge carrier concentration in organic bulk heterojunction solar cells — •Daniel Rauh1, Alexander Wagenpfahl2, Carsten Deibel2, and Vladimir Dyakonov1,2 — 1Bavarian Centre for Applied Energy Research e.V. (ZAE Bayern), D-97074 Würzburg — 2Julius-Maximilians-University of Würzburg, Institute of Physics, Experimental Physics VI, D-97074 Würzburg
A deeper understanding of the open circuit voltage Voc in bulk heterojunction solar cells is crucial for further performance enhancements. In order to investigate Voc, we measured temperature dependent current–voltage characteristics of poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) solar cells (pristine and annealed) at various light intensities. With charge extraction measurements under the same conditions we could determine the corresponding charge carrier densities n in the operating device. Extrapolating Voc to T=0K gives a constant value for all intensities indicating the effective bandgap of the donor–acceptor system. Fitting the data with Voc models [1,2] showed excellent agreement with only one free parameter, the effective density of states. From our analysis, we gain insights into the recombination meachanisms limiting Voc.
[1] Koster et al., Appl. Phys. Lett. 86, 123509 (2005)
[2] Cheyns et al., Phys. Rev. B 77, 165332 (2008)
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