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 18.3: Talk

Monday, March 22, 2010, 16:30–16:45, H15

Oxygen Induced Degradation of P3HT:PCBM Solar Cells — •Julia Schafferhans, Stefan Neugebauer, Andreas Baumann, Alexander Wagenpfahl, Carsten Deibel, and Vladimir Dyakonov — Experimental Physics VI, Faculty of Physics and Astronomy, Julius-Maximilians-University of Würzburg, Am Hubland, 97074 Würzburg, Germany

Power conversion efficiencies of 6% for organic solar cells have already been achieved, with growing tendency. A critical issue yet to be addressed are the factors influencing the device lifetime. To gain a detailed understanding of the device stability, the underlying degradation mechanisms and their impact on the solar cell performance is an important prerequisite for lifetime enhancement. We investigated the oxygen induced degradation of state of the art (PCE > 3%) P3HT:PCBM (poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester) solar cells in the dark as well as under simultaneous illumination. Current--Voltage measurements are supplemented by Thermally Stimulated Current (TSC) and Charge Extraction by Linearly Increasing Voltage (CELIV) measurements. In the case of dark degradation the influence of oxygen results in a decrease of the short circuit current (Isc), whereas degradation under bias light leads to a decrease of all solar cell parameters. With the aid of a macroscopic simulation we demonstrate that the origin of the loss in Isc is oxygen doping, which we confirmed by CELIV measurements. In addition, TSC and CELIV measurements revealed an increase of deeper traps and a slight decrease of the mobility due to oxygen.