Molecular Engineering of Fano Resonances for Enhanced Single-Molecule Thermoelectrics
4 affiliations
- 1National Center for Nanoscience and Technology
- 2Institute of Chemistry, Chinese Academy of Sciences
- 3College of Chemistry and Chemical Engineering & Institute of Artificial Intelligence & Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, P. R. China.
- 4Nanyang Technological University
Abstract
Enhancing the thermoelectric power factor of single-molecule junctions requires simultaneously achieving high electrical conductance and thermopower, which are often mutually constrained. The sharp and asymmetric transmission features produced by Fano resonances offer a promising strategy for mitigating this trade-off. However, quantitative molecular structure–line-shape relationships linking molecular modifications to the resonance valley position and peak-valley energy width remain underexplored. Here, we demonstrate a molecular engineering strategy based on electronically tunable 9-fluorenylidene derivatives to tailor Fano resonance line shapes in single-molecule junctions. Systematic density functional theory and non-equilibrium Green’s function (DFT-NEGF) calculations reveal that substituent-induced variations in local orbital energies, backbone-side-chain coupling and localized-delocalized state detuning control the resonance valley position and the peak-valley energy width. Specifically, the valley position correlates linearly with the energy level of the side-group-localized LUMO, whereas the width is governed by the combined effect of main-side-chain coupling and localized-delocalized state detuning. Together, these two orbital descriptors provide a practical basis for the predictive molecular engineering of Fano resonance line shapes. To experimentally validate this strategy, we synthesized and characterized the designed dicyanomethylene-substituted derivative C -(CN) 2 alongside a control molecule A -O . Electrochemically controlled scanning tunneling microscope break-junction (EC-STM-BJ) measurements confirm the emergence of Fano resonance features near the Fermi level for C -(CN) 2 , in agreement with the DFT-NEGF prediction, whereas no comparable features is observed for A -O. Crucially, statistical single-molecule conductance and thermopower measurements reveal that C -(CN) 2 simultaneously exhibits higher conductance ( G ) and Seebeck coefficient ( S ) than A -O , overcoming the usual trade-off between these two parameters. This synergy effect yields a 97.6% enhancement in thermoelectric power factor ( GS 2 ) relative to control systems. By establishing explicit structure–line-shape–property relationships, this work provides a practical molecular engineering strategy for engineering Fano resonances in single-molecule thermoelectrics.
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BibTeX
@misc{ding2026molecular,
title = {{Molecular Engineering of Fano Resonances for Enhanced Single-Molecule Thermoelectrics}},
author = {Qianyu Ding and Kai Song and Weichen Bai and Mingchen Liang and Wei Hao and Yaping Zang and Junyang Liu and Shuzhou Li and Jia Zhu and Daoben Zhu},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv-2025-mg5hc/v2},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv-2025-mg5hc/v2},
note = {CC BY},
}
RIS
TY - UNPB
TI - Molecular Engineering of Fano Resonances for Enhanced Single-Molecule Thermoelectrics
AU - Qianyu Ding
AU - Kai Song
AU - Weichen Bai
AU - Mingchen Liang
AU - Wei Hao
AU - Yaping Zang
AU - Junyang Liu
AU - Shuzhou Li
AU - Jia Zhu
AU - Daoben Zhu
PY - 2026
DA - 2026/10/12
PB - ChemRxiv
DO - 10.26434/chemrxiv-2025-mg5hc/v2
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv-2025-mg5hc/v2
AB - Enhancing the thermoelectric power factor of single-molecule junctions requires simultaneously achieving high electrical conductance and thermopower, which are often mutually constrained. The sharp and asymmetric transmission features produced by Fano resonances offer a promising strategy for mitigating this trade-off. However, quantitative molecular structure–line-shape relationships linking molecular modifications to the resonance valley position and peak-valley energy width remain underexplored. Here, we demonstrate a molecular engineering strategy based on electronically tunable 9-fluorenylidene derivatives to tailor Fano resonance line shapes in single-molecule junctions. Systematic density functional theory and non-equilibrium Green’s function (DFT-NEGF) calculations reveal that substituent-induced variations in local orbital energies, backbone-side-chain coupling and localized-delocalized state detuning control the resonance valley position and the peak-valley energy width. Specifically, the valley position correlates linearly with the energy level of the side-group-localized LUMO, whereas the width is governed by the combined effect of main-side-chain coupling and localized-delocalized state detuning. Together, these two orbital descriptors provide a practical basis for the predictive molecular engineering of Fano resonance line shapes. To experimentally validate this strategy, we synthesized and characterized the designed dicyanomethylene-substituted derivative C -(CN) 2 alongside a control molecule A -O . Electrochemically controlled scanning tunneling microscope break-junction (EC-STM-BJ) measurements confirm the emergence of Fano resonance features near the Fermi level for C -(CN) 2 , in agreement with the DFT-NEGF prediction, whereas no comparable features is observed for A -O. Crucially, statistical single-molecule conductance and thermopower measurements reveal that C -(CN) 2 simultaneously exhibits higher conductance ( G ) and Seebeck coefficient ( S ) than A -O , overcoming the usual trade-off between these two parameters. This synergy effect yields a 97.6% enhancement in thermoelectric power factor ( GS 2 ) relative to control systems. By establishing explicit structure–line-shape–property relationships, this work provides a practical molecular engineering strategy for engineering Fano resonances in single-molecule thermoelectrics.
ER -