Dresden 2009 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 33: Organic Photovoltaics II
CPP 33.7: Vortrag
Donnerstag, 26. März 2009, 15:30–15:45, ZEU 222
Investigation of ageing processes in bulk-heterojunction P3HT:PCBM organic solar cells by means of impedance spectroscopy — •Uli Würfel1,3, Bas v. d. Wiel2, Birger Zimmermann1,3, and Michael Niggemann3 — 1Freiburg Materials Research Centre, Freiburg, Germany — 2Universiteit Utrecht, Netherlands — 3Fraunhofer Institute for Solar Energy Systems, Freiburg, Germany
The improvement of the long term stability is one important task in the development of organic photovoltaic (OPV) devices. Although promising device stabilities in the order of years can be expected the degradation mechanisms are not understood completely. They have to be identified to define conditions for accelerated degradation experiments to predict the lifetime of a device. Oxygen and water are well known as most harmful chemical species for OPV devices. We will present results of accelerated ageing experiments done on bulk-heterojunction P3HT:PCBM solar cells. The cells were placed in a gas tight flow cell and exposed either to ambient air, pure dry oxygen or nitrogen saturated with water vapour. They were repeatedly measured by recording dark and illuminated current-voltage characteristics and a series of impedance spectra for different applied bias voltages. By means of the impedance spectra it is possible to distinguish between different degradation phenomena - like e.g. doping and interface degradation - and gain a deeper understanding of the underlying processes. Finally, simulations were carried out to model the change in the physical properties of the organic semiconductor and its impact on the device performance.