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HL: Fachverband Halbleiterphysik

HL 90: Poster III

HL 90.30: Poster

Donnerstag, 10. März 2016, 16:00–19:00, Poster A

Efficient dissociation of charge transfer states in PTB7-based organic solar cells — •Marina Gerhard¹, Andreas P. Arndt², Ian A. Howard³, Mühenad Bilal¹, Arash Rahimi-Iman¹, Uli Lemmer^2,3, and Martin Koch¹ — ¹Faculty of Physics and Materials Sciences Center, Philipps-Universität Marburg, 35032 Marburg, Germany — ²Light Technology Institute, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany — ³Institute of Microstructure Technology, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany

In organic solar cells, interfacial charge transfer (CT) states can either act as precursors for free charges or possess trapping character, enhancing geminate recombination. Here, we present a study on the polymer PTB7, blended with the fullerene derivative PC₇₁BM, where we investigate interfacial recombination by means of time-resolved photoluminescence^[1]. Our results on the temperature- and energy-dependent decay dynamics suggest that there is a kinetic competition between charge separation and CT recombination. We find low activation barriers for CT quenching in the range of k · T at room temperature, indicating that the CT states are only weakly bound. This is consistent with our recent experimental work on field-induced CT quenching. Furthermore, we observe that the nanomorphology has a strong influence on the efficiency of charge separation, because the CT emission yield is much higher after selective excitation of the polymer rather than for preferential excitation of pure fullerene domains.

[1] J. Phys. Chem. C, DOI: 10.1021/acs.jpcc.5b09842 (2015)