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SYOH: Organic and Hybrid Systems for Future Electronics

SYOH 5: Poster

SYOH 5.49: Poster

Donnerstag, 11. März 2004, 18:00–21:00, B

Photophysical properties of annealed polyhexylthiophen:fullerene composites — •Michael Pientka, Dana Chirvase, and Vladimir Dyakonov — Institute of Physics, University of Oldenburg, 26111 Oldenburg, Germany

Composites of polyhexylthiophen and methanofullerene (PCBM) are promising for polymer photovoltaics. External quantum efficiences above 70% and power conversion efficiences above 3% were demonstated recently. Decisive step to achieve such high values is a thermal annealing, strongly improving the electrical performance. The exact nature of this effect is still under discussion. We apply photoinduced absorption, light induced electron spin resonance and photoluminescence spectroscopy for the investigation of the photogenerated states and their transformation upon annealing. The heat treatment leads to a number of effects: increase of the photoluminescence previously suppressed, energy shift of polaronic absorption band together with a strong increase in the density of charge separated states. The changes observed are discussed in terms of variation of nanomorphology in polymer-fullerene blends, as supported by AFM, and are related to device performance.