Hamburg 2001 – wissenschaftliches Programm
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SYOF: Organische Festkörper
SYOF 5: Poster Session
SYOF 5.11: Poster
Dienstag, 27. März 2001, 17:00–19:00, Aula S3
Controlled Doping of Polycrystalline and Amorphous ZnPc (Zinc-Phthalocyanine): A Systematic Seebeck and Field-Effect Study — •Bert Männig, Martin Pfeiffer, Andreas Nollau, and Karl Leo — Institut für Angewandte Photophysik, TU Dresden, D-01062 Dresden, Germany
Organic dyes with conjugated electron systems are currently investigated intensively for optoelectronic applications. Amorphous materials are popular mainly because they form smooth layers and do not degrade by crystallization (if the glass transition temperature is high enough). We present here the results of a comprehensive study of controlled p-type doping of polycrystalline and amorphous ZnPc (zinc-phthalocyanine) by the strong organic acceptor F4-TCNQ (tetrafluoro-tetracyano- quinodimethane). Doping is more efficient for the polycrystalline phase where doping enhances the conductivity by up to eight orders of magnitude (10−2 S/cm). Nevertheless, we could show for the first time that also amorphous phthalocyanine layers (deposited onto cooled substrates) can be doped, i.e. their conductivity increases and their Seebeck coefficient decreases indicating a shift of the Fermi level towards the hole transport state. The field-effect mobility determined in thin film transistors increases with increasing doping ratio. With a simple model assuming only one relevant transport level we obtain a good agreement between the Seebeck and the field-effect measurements.