Dresden 2014 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 29: Poster: Organic semiconductors and hybrid organic-inorganic heterostructures / Organic photovoltaics
HL 29.7: Poster
Monday, March 31, 2014, 17:00–20:00, P2
Time-resolved spectroscopy of interfacial states in P3HT-PCBM blends — •Marina Gerhard1, Andreas Arndt2, Aina Quintilla2, Ulrich Lemmer2, and Martin Koch1 — 1Faculty of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, D-35032 Marburg, Germany — 2Light Technology Institute, Universität Karlsruhe, Kaiserstrasse 12, D-76131 Karlsruhe, Germany
We have studied the time-resolved photoluminescence (PL) of organic donor-acceptor bulk heterojunctions based on the polymer poly(3-hexylthiophene) (P3HT) blended with varying concentrations of the fullerene derivative [6,6]-phenyl-C61 butyric acid methyl ester (PCBM). Those blends represent a well-known material for potential solar cell applications. By comparing the emission of the blends to that obtained for neat polymer and fullerene films, most of the contributions could be allocated to radiative recombination inside the polymer domains. In addition, we identified a weak but slower decaying signature in the IR-regime that was only present in the blends. We thus attributed this feature to carriers recombining at the interfaces between donor and acceptor. Currently, the role of such interfacial "charge transfer" states in the process of free carrier generation is intensely being discussed. We discovered that the dynamics of the interfacial state was almost independent of temperature and excitation density. These findings indicate that the electrons and holes which cause the interfacial PL-emission are trapped inside isolated states where further diffusion is unlikely.