Experimental Studies on the Anisotropic Thermoelectric Properties of Conducting Polymer Films

We reported general methods for studying the thermoelectric properties of a polymer film in both the in-plane and through-plane directions. The bench-mark PEDOT/PSS films have highly anisotropic carrier transport properties and thermal conductivity. The anisotropic carrier transport properties can be explained by the lamellar structure of the PEDOT/PSS films where the PEDOT nanocrystals could be isolated by the insulating PSS in the through-plane direction. The anisotropic thermal conductivity was mainly attributed to the lattice contribution from PSS because the polymer chain is oriented along the substrate

Thermoelectric Efficiency of Organometallic Complex Wires via Quantum Resonance Effect and Long-Range Electric Transport Property

Superior long-range electric transport has been observed in several organometallic wires. Here, we discuss the role of the metal center in the electric transport and examine the possibility of high thermoelectric figure of merit (<i>ZT</i>) by controlling the quantum resonance effects. We examined a few metal center (and metal-free) terpyridine-based complexes by first-principles calculations and clarified the role of the metals in determining the transport properties. Quasi-resonant tunneling is mediated by organic compounds, and narrow overlapping resonance states are formed when d<i>-</i>electron metal centers are incorporated. Distinct length (<i>L</i>) and temperature (<i>T</i>) dependencies of thermopower from semiconductor materials or organic molecular junctions are presented in terms of atomistic calculations of <i>ZT</i> with and without considering the phonon thermal conductance. We present an alternative approach to obtain high <i>ZT</i> for molecular junctions by quantum effect

Long-Range Electron Transport of Ruthenium-Centered Multilayer Films <i>via</i> a Stepping-Stone Mechanism

We studied electron transport of Ru complex multilayer films, whose structure resembles redox-active complex films known in the literature to have long-range electron transport abilities. Hydrogen bond formation in terms of pH control was used to induce spontaneous growth of a Ru complex multilayer. We made a cross-check between electrochemical measurements and <i>I–V</i> measurements using PEDOT:PSS to eliminate the risk of pinhole contributions to the mechanism and have found small β values of 0.012–0.021 Å^–1. Our Ru complex layers exhibit long-range electron transport but with low conductance. On the basis of the results of our theoretical–experimental collaboration, we propose a modified tunneling mechanism named the “stepping-stone mechanism”, where the alignment of site potentials forms a narrow band around <i>E</i>_F, making resonant tunneling possible. Our observations may support Tuccito <i>et al</i>.’s proposed mechanism

Potential Tuning of Nanoarchitectures Based on Phthalocyanine Nanopillars: Construction of Effective Photocurrent Generation Systems

Nanopillars composed of a photoresponsive phthalocyanine derivative have been conveniently fabricated using a continuous silane coupling reaction on a substrate. The chemical potentials of phthalocyanine nanopillars (PNs) are precisely controlled by changing the number of phthalocyanine derivatives on the substrate. In addition, photocurrent generation efficiencies have been strongly influenced by the number of phthalocyanine derivatives. High photocurrent conversion cells in a solid state have been obtained by the combination of PNs and a fullerene derivative

Self-Aligned Formation of Sub 1 nm Gaps Utilizing Electromigration during Metal Deposition

We developed a procedure for the fabrication of sub 1 nm gap Au electrodes via electromigration. Self-aligned nanogap formation was achieved by applying a bias voltage, which causes electromigration during metal evaporation. We also demonstrated the application of this method for the formation of nanogaps as small as 1 nm in width, and we found that the gap size can be controlled by changing the magnitude of the applied voltage. On the basis of the electric conductance and surface-enhanced Raman scattering (SERS) measurements, the fabricated gap size was estimated to be nearly equal to the molecular length of 1,4-benzenedithiol (BDT). Compared with existing electromigration methods, the new method provides two advantages: the process currents are clearly suppressed and parallel or large area production is possible. This simple method for the fabrication of a sub 1 nm gap electrode is useful for single-molecule-sized electronics and opens the door to future research on integrated sub 1 nm sized nanogap devices