SKM 2023 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 16: Thermoelectric and Phase Change Materials; Layer Deposition

DS 16.6: Vortrag

Donnerstag, 30. März 2023, 12:45–13:00, SCH A 315

Seebeck coefficient inversion in highly doped organic semiconductors — •Morteza Shokrani¹, Kai Xu², Tero-Petri Ruoko², Dorothea Scheunemann¹, Hassan Abdalla², Hengda Sun², Chi-Yuan Yang², Yuttapoom Puttisong², Nagesh Kolhe³, José Silvestre Mendoza Figueroa², Jonas Pedersen², Thomas Ederth², Weimin Chen², Magnus Berggren², Samson Jenekhe³, Daniele Fazzi⁴, Martijn Kemerink^1,2, and Simone Fabiano² — ¹Heidelberg University, Germany — ²Linköping University, Sweden — ³University of Washington, USA — ⁴University of Cologne, Germany

The investigation of the thermoelectric properties of organic semiconductors (OSC) with the aim of increasing their efficiency as active material in thermoelectric generators has attracted attention for the past years. The maximum efficiency of the energy conversion process in a thermoelectric material is set by zT, which is proportional to electrical conductivity and Seebeck coefficient (S) squared. A common way of increasing zT is by doping, which typically increases the charge carrier density and electrical conductivity, while decreasing S. The sign of S is often used to determine the polarity of the majority charge carriers in OSC. In recent years, a surprising change in the sign of S has sometimes been observed to occur in highly doped OSC. Here, by combining conductivity and S measurements with kinetic Monte Carlo simulations, it is shown that density of state filling in combination with the opening of a hard Coulomb gap around the Fermi energy is responsible for the sign inversion