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Direct Measurement of the Effective Electronic Temperature in Organic Semiconductors

Anton Kompatscher and Martijn Kemerink*

  • Institute for Molecular Systems Engineering and Advanced Materials, Heidelberg University, Im Neuenheimer Feld 225, 69120 Heidelberg, Germany

  • *Contact author: martijn.kemerink@uni-heidelberg.de
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Phys. Rev. Lett. 135, 226301 – Published 24 November, 2025

DOI: https://doi.org/10.1103/rgt1-789y

Abstract

Organic semiconductors show complex phenomena due to their high energetic disorder. A striking example is the possibility of an increased effective temperature Teff of the charge carrier distribution relative to the lattice temperature, which results from the slow charge carrier relaxation after excitation, either by high electric field or photon absorption. The increased effective temperature has been linked to conductivity enhancements and performance increases in actual devices, but a direct observation has been lacking. Here, we utilize nanoscopic tree-terminal devices to measure the Seebeck voltage arising in a doped organic polymer semiconductor due to a field-driven enhancement of the effective electronic temperature, providing direct proof of the existence of Teff. The results agree quantitatively with numerical predictions by a kinetic Monte Carlo model. The findings not only provide fundamental understanding but also indicate an avenue toward low-loss thermoelectric devices.

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Phys. Rev. Lett. 135, 226301– Published 24 November, 2025
  • Received 20 March 2025
  • Revised 4 October 2025
  • Accepted 14 October 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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