Thermopower in Transition from Tunneling to Hopping

Sohyun Park, Jeong Woo Jo, Jiung Jang, Tatsuhiko Ohto, Hirokazu Tada, Hyo Jae Yoon

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


The Seebeck effect of a molecular junction in a hopping regime or tunneling-to-hopping transition remains uncertain. This paper describes the Seebeck effect in molecular epitaxy films (OPInwhere n = 1-9) based on imine condensation between an aryl amine and aldehyde and investigates how the Seebeck coefficient (S, μV/K) varies at the crossover region. The S value of OPInlinearly increased with increasing the molecular length (d, nm), ranging from 7.2 to 38.0 μV/K. The increasing rate changed from 0.99 to 0.38 μV·K-1Å-1at d = 3.4 nm (OPI4). Combined experimental and theoretical studies indicated that such a change stems from a tunneling-to-hopping transition, and the small but detectable length-dependence of thermopower in the long molecules originates from the gradual reduction of the tunneling contribution to the broadening of molecular orbital energy level, rather than its relative position to the Fermi level. Our work helps to bridge the gap between bulk and nanoscale thermoelectric systems.

Original languageEnglish
Pages (from-to)7682-7689
Number of pages8
JournalNano Letters
Issue number18
Publication statusPublished - 2022 Sept 28


  • hopping
  • molecular junction
  • Seebeck coefficient
  • thermopower
  • transition
  • tunneling

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering


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