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HL: Fachverband Halbleiterphysik

HL 45: Organic electronics and photovoltaics: OPV II (CPP with HL/TT)

HL 45.6: Vortrag

Mittwoch, 18. März 2015, 10:45–11:00, C 130

Efficiency-Limiting Processes in Low-Bandgap Polymer:Perylene Diimide Photovoltaic Blends — •Dominik Gehrig¹, Steffen Roland², Ian Howard¹, Dieter Neher², and Frédéric Laquai¹ — ¹Max-Planck-Institut für Polymerforschung, Mainz — ²Institut für Physik und Astronomie, Physik weicher Materie, Universität Potsdam

In this work, we present a photophysical study on blends of a low-bandgap polymer, namely PBDTTT-C, as donor in combination with a PDI-based electron acceptor.[1] Exciton and charge carrier dynamics as well as loss mechanisms are investigated by sub-picosecond to microsecond pump-probe transient absorption (TA) and time-resolved photoluminescence (TRPL) spectroscopy in combination with multivariate curve resolution (MCR) data analysis. A largely diffusion-limited exciton dissociation at the donor acceptor interface and consequently a slow charge generation is observed. Time-delayed collection field (TDCF) experiments reveal a strongly field-dependent charge generation process in turn leading to low fill factors in devices. However, once free charges are generated they recombine non-geminately on a ns-us timescale indicating that they can be potentially extracted as photocurrent. By comparison of the PBDTTT-C:PDI charge generation efficiency with that of a PBDTTT-C:fullerene blend, we identify inefficient charge generation and fast non-geminate recombination competing with charge extraction to be the main bottlenecks of photocurrent generation in the investigated polymer:PDI blends.

[1] Gehrig et al., J. Phys. Chem. C 2014, 118, 20077