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HL: Fachverband Halbleiterphysik
HL 17: Organic Semiconductors
HL 17.7: Talk
Tuesday, March 19, 2024, 11:15–11:30, EW 015
Interplay of Electrical Conductivity and Seebeck Coefficient of n-doped NDI-based Polymer Thin Films for Thermoelectric Applications — •Marie Siegert1, Markus Hönig2, Michael Sommer2, and Jens Pflaum1,3 — 1University of Würzburg — 2Chemnitz University of Technology — 3CAE Bayern
Thermoelectric generators based on organic materials offer a sustainable, low-cost approach towards waste heat recovery and thus, efficient energy consumption. Disordered polymer thin films in particular exhibit aptly low thermal conductivties κ for thermoelectric applications and their preparation via solution processing is easily scaled to meet industrial requirements. To improve their inherently low charge carrier concentration and therefore increase their electrical conductivity σ, suitable dopants can be employed. However, doping typically causes the Seebeck coefficent S to decrease, and may even lead to a polarity change in S at high doping concentrations, which is detrimental to thermoelectric efficiency. Here we conducted temperature dependent studies on thin films of the polymer PNDIT2 utilizing the n-type dopant TAM with regards to their thermoelectric properties. Systematically varying the molecular weight of the PNDIT2 host, the interplay of charge carrier density and mobility in this polymeric system and their effect on the Seebeck coefficient are revealed. The resulting power factors PF = σ S2 suggest future strategies to further refine the doping protocol for polymer thin films and thus, to maximize their thermoelectric figure of merit. The Deutsche Bundesstiftung Umwelt (DBU) is acknowledged for financial support.
Keywords: Thermoelectrics; Polymer Thin Films; Doped Polymers; Seebeck Coefficient; PNDIT2