Enhanced Thermopower of Saturated Molecules by Noncovalent Anchor‐Induced Electron Doping of Single‐Layer Graphene Electrode

Abstract

Enhancing thermopower is a key goal in organic and molecular thermoelectrics. Herein, it is shown that introducing noncovalent contact with a single-layer graphene (SLG) electrode improves the thermopower of saturated molecules as compared to the traditional gold-thiolate covalent contact. Thermoelectric junction measurements with a liquid-metal technique reveal that the value of Seebeck coefficient in large-area junctions based on n-alkylamine self-assembled monolayers (SAMs) on SLG is increased up to fivefold compared to the analogous junction based on n-alkanethiolate SAMs on gold. Experiments with Raman spectroscopy and field-effect transistor analysis indicate that such enhancements benefit from the creation of new in-gap states and electron doping through noncovalent interaction between the amine anchor and the SLG electrode, which leads to a reduced energy offset between the Fermi level and the transport channel. This work demonstrates that control of interfacial bonding nature in molecular junctions improves the Seebeck effect in saturated molecules.

Electrostatic Fermi level tuning in large-scale self-assembled monolayers of oligo(phenylene–ethynylene) derivatives

“…The field of molecular electronics, which aims to use molecules as basic building blocks for electronic devices, is of considerable current interest due to its potential for designing logic gates, sensors, memory devices and thermoelectric energy harvesters on the nanometer scale. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] The testbeds for molecular-electronic measurements are either single-molecule junctions or large-scale molecular thin films formed from…”

“…The field of molecular electronics, which aims to use molecules as basic building blocks for electronic devices, is of considerable current interest due to its potential for designing logic gates, sensors, memory devices and thermoelectric energy harvesters on the nanometer scale. 1–16 The testbeds for molecular-electronic measurements are either single-molecule junctions or large-scale molecular thin films formed from self-assembled monolayers (SAMs). 17–29 The central challenge for single-molecule electronics is the uncertainty in the binding geometry of single molecules located between two electrodes.…”

Thermopower in Transition from Tunneling to Hopping

“…Molecular epitaxystepwise growth of (semi)­crystalline molecular overlayer on a substrateis useful for fabricating molecular thin films composed of vertically aligned, ordered oligomers from monomers. , Here, we show thermopower measurements over molecular junctions based on molecular epitaxy of an oligophenyleneimine (OPI n where n = 1–9) layer, formed via imine condensation between aryl aldehyde and amine derivatives on an ultrasmooth template-stripped gold (Au TS ) substrate (Figure ), , using eutectic Ga–In (EGaIn) for a top electrode (Figure ). ,− As the number of epitaxy cycles ( n in OPI n ) increased, the Seebeck coefficient ( S , μV/K) increased linearly. Notably, we observed a noticeable transition in the increasing rate at the point of n = 4 (length of molecule ( d ) = 3.4 nm), which was attributed to the transition in the charge transport regime from tunneling to hopping.…”

Transformable Gallium‐Based Liquid Metal Nanoparticles for Tumor Radiotherapy Sensitization

“…toxicity, which enable their suitability not only for microfluidics, printed circuits, flexible electronics, and artificial intelligence, but also for biomedical applications. [10][11][12][13][14][15][16][17][18][19][20] Compared with "hard" NPs, "soft" NPs like Gallium and Gallium-Indium eutectic alloys (EGaIn, 75% Ga, 25% In, wt%) with moderate melting points (29.8 °C, 15.7 °C, respectively) possess good biocompatibility and low toxicity. More importantly, their mechanical parameters are close to biological tissue, which allows their in vivo administration, acrossing the biological barrier, and increased tissue retention.…”