Seebeck Effect in Molecular Wires Facilitating Long-Range Transport

초록

The study of molecular wires facilitating long-range charge transport is of fundamental interest for the development of various technologies in (bio)-organic and molecular electronics. Defining the nature of long-range charge transport is challenging as electrical characterization does not offer the ability to distinguish a tunneling mechanism from the other. Here, we show that investigation of the Seebeck effect provides the ability. We examine the length dependence of the Seebeck coefficient in electrografted bis-terpyridine Ru-(II) complex films. The Seebeck coefficient ranges from 307 to 1027 mu V/K, with an increasing rate of 95.7 mu V/(K nm) as the film thickness increases to 10 nm. Quantum-chemical calculations unveil that the nearly overlapped molecular-orbital energy level of the Ru complex with the Fermi level accounts for the giant thermopower. Landauer-Bu''ttiker probe simulations indicate that the significant length dependence evinces the Seebeck effect dominated by coherent near-resonant tunneling rather than thermal hopping. This study enhances our comprehension of long-range charge transport, paving the way for efficient electronic and thermoelectric materials.

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