Regensburg 2010 – scientific programme
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O: Fachverband Oberflächenphysik
O 18: [HL] Organic Semiconductors: Solar Cells (Joint Session DS/CPP/HL/O)
O 18.1: Talk
Monday, March 22, 2010, 16:00–16:15, H15
Pulsed Photocurrent Measurements in Bulk Heterojunction Solar Cells — •Markus Mingebach1, Moritz Limpinsel1, Alexander Wagenpfahl1, Alexander Goldmann1, Carsten Deibel1, and Vladimir Dyakonov1,2 — 1Experimental Physics VI, Physical Institute, Julius-Maximilians-University of Würzburg, Am Hubland, D-97074 Würzburg — 2Centre of Applied Energy Research (ZAE Bayern e. V.), Am Hubland, D-97074 Würzburg
The performance of organic bulk heterojunction solar cells greatly improved during the last years up to 6% power conversion efficiency. Nevertheless very important properties such as the voltage dependent photocurrent are not fully understood yet. We investigate the photocurrent in poly(3-hexyl thiophene) (P3HT) : [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) solar cells by applying a pulsed measurement technique (proposed by Ooi et al.) and also find a point of optimal symmetry (POS) at 0.52-0.64 V. In contrast to Ooi we identify this voltage not as the built-in voltage, but as the case of flat bands in the bulk of the cell (confirmed by macroscopic simulations). [1] To explain the voltage dependent photocurrent, we apply a combination of Onsager–Braun (polaron pair dissociation) and Sokel–Hughes (charge carrier extraction) theory in conjunction with the POS. In addition we observe and investigate a voltage-independent offset of the photocurrent, which is crucial for optimizing the device performance.
[1] M. Limpinsel, A. Wagenpfahl, M. Mingebach, C. Deibel and V. Dyakonov, Investigation of the Photocurrent in Bulk Heterojunction Solar Cells, submitted (2009).
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