Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 31: Organic semiconductors
HL 31.13: Vortrag
Mittwoch, 29. März 2006, 17:45–18:00, POT 51
Influence of the active layer morphology on the device performance of polymer-fullerene bulk heterojunction solar cells — •Ingo Riedel1, Carsten Deibel2, and Vladimir Dyakonov1,2 — 1Bavarian Centre for Applied Energy Research (ZAE-Bayern e.V.), Div. Funtional Materials for Energy Technology, Am Hubland, D-97074 Würzburg — 2Experimental Physics VI, Institute of Physics, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
Recent achievements in organic photovoltaics demonstrate the high potential of using polymer-fullerene blends, such as P3HT:PCBM, as photoactive films for PV applications. Blending of the two materials introduces new effects, which have direct impact on the performance of the solar cell: Thermal annealing of P3HT:PCBM devices results in drastic efficiency improvement. The relevant effect is a thermally induced ordering of the P3HT phase, accompanied with molecular diffusion of PCBM out of the polymer matrix to form isolated semicrystalline domains. Their size and concentration is correlated with the amount of PCBM available. We show that the nanoscaled morphology additionally influences the open circuit voltage VOC. This is shown by comparing devices based on two fullerene derivatives with identical redox potentials, each blended with the same donor polymer. Films of both composites exhibit different morphologies, which are represented by different values of VOC. Analysis of the dark diode characteristics yields different ideality factors, which reflect the dominant internal recombination mechanism, e.g., electron back transfer from the fullerene moiety into the polymer phase.