Hannover 2010 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 5: Femtosecond Spectroscopy I
MO 5.8: Vortrag
Dienstag, 9. März 2010, 15:45–16:00, F 102
Influence of structure and morphology of ZnPc:C60 films on charge carrier dynamics studied by terahertz spectroscopy — •Christian Strothkämper, Rainer Eichberger, Thomas Hannappel, and Andreas Bartelt — Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
We used optical pump terahertz probe (OPTP) spectroscopy to examine the influence of structure and morphology on the conductivity of thin blended zinc phtalocyanine (ZnPc) C60 films with a molecular ratio of 1:1. We were able to measure the photoinduced conductivity on sub-ps to ns timescale and on ZnPc:C60 films with a thickness of 200nm which are comparable to real photovoltaic devices. The decay of the conductivity can be described by a multiexponential fit with the longest decay components on the order of several ns. The morphology and structure can be changed by varying the substrate temperature during evaporation of the components. Recently, the formation of crystalline C60 and ZnPc domains with increasing substrate temperature was observed with TEM. The decay of the conductivity is correlated to the film morphology and is slowed down with improved sample morphology and structure. Our results suggest that the lifetime of separated charge carriers in the crystalline domains is enhanced due to the reduction of interfacial recombination. No photoconductivity was observed in neat ZnPc and C60 films, indicating that the interfaces are necessary for the generation of mobile charge carriers.