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O'Driscoll LJ, Jay M, Robinson BJ, Sadeghi H, Wang X, Penhale-Jones B, Bryce MR, Lambert CJ. Planar aromatic anchors control the electrical conductance of gold|molecule|graphene junctions. NANOSCALE ADVANCES 2023; 5:2299-2306. [PMID: 37056609 PMCID: PMC10089101 DOI: 10.1039/d2na00873d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 03/08/2023] [Indexed: 06/19/2023]
Abstract
The synthesis of a family of alkanethiol molecules with planar aromatic head groups, designed to anchor molecules effectively to graphene electrodes, is reported. Characterisation of self-assembled monolayers of these molecules on a gold surface via conductive atomic force microscopy shows that when an aromatic head group is present, the conductance G graphene obtained using a graphene coated probe is higher than the conductance G Pt obtained using a platinum (Pt) probe. For Pt probe and graphene probe junctions, the tunnelling decay constant of benzyl ether derivatives with an alkanethiol molecular backbone is determined as β = 5.6 nm-1 and 3.5 nm-1, respectively. The conductance ratio G graphene/G Pt increases as the number of rings present in the aromatic head unit, n, increases. However, as the number of rings increases, the conductance path length increases because the planar head groups lie at an angle to the plane of the electrodes. This means that overall conductance decreases as n increases. Density functional theory-based charge transport calculations support these experimental findings. This study confirms that planar aromatic head groups can function as effective anchoring units for graphene electrodes in large area molecular junctions. However, the results also indicate that the size and geometry of these head groups must be considered in order to produce effective molecular designs.
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Affiliation(s)
| | - Michael Jay
- Dept. of Physics, Lancaster University Lancaster LA1 4YB UK
| | | | - Hatef Sadeghi
- Dept. of Engineering, Warwick University Coventry CV4 7AL UK
| | - Xintai Wang
- School of Information Science and Technology, Dalian Maritime University Dalian China
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Sengul O, Valli A, Stadler R. Electrode effects on the observability of destructive quantum interference in single-molecule junctions. NANOSCALE 2021; 13:17011-17021. [PMID: 34617536 DOI: 10.1039/d1nr01230d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Destructive quantum interference (QI) has been a source of interest as a new paradigm for molecular electronics as the electronic conductance is widely dependent on the occurrence or absence of destructive QI effects. In order to interpret experimentally observed transmission features, it is necessary to understand the effects of all components of the junction on electron transport. We perform non-equilibrium Green's function calculations within the framework of density functional theory to assess the structure-function relationship of transport through pyrene molecular junctions with distinct QI properties. The chemical nature of the anchor groups and the electrodes controls the Fermi level alignment, which determines the observability of destructive QI. A thorough analysis allows to disentangle the transmission features arising from the molecule and the electrodes. Interestingly, graphene electrodes introduce features in the low-bias regime, which can either mask or be misinterpreted as QI effects, while instead originating from the topological properties of the edges. Thus, this first principles analysis provides clear indications to guide the interpretation of experimental studies, which cannot be obtained from simple Hückel model calculations.
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Affiliation(s)
- Ozlem Sengul
- Institute for Theoretical Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria.
| | - Angelo Valli
- Institute for Theoretical Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria.
| | - Robert Stadler
- Institute for Theoretical Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria.
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Gao T, He C, Liu C, Fan Y, Zhao C, Zhao C, Su W, Dappe YJ, Yang L. Oligothiophene molecular wires at graphene-based molecular junctions. Phys Chem Chem Phys 2021; 23:21163-21171. [PMID: 34528653 DOI: 10.1039/d1cp03050g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The use of graphene as a new type of electrode at molecular junctions has led to a renewal of molecular electronics. Indeed, the symmetry breaking induced by the graphene electrode yields different electronic behaviors at the molecular junction and in particular enhanced conductance for longer molecules. In this respect, several studies involving different molecular backbones and anchoring groups have been performed. Here in the same line, we consider oligopthiophene based hybrid gold-graphene junctions and we measure their electrical properties using the STM-I(s) method in order to determine their attenuation factor and the effect of specific anchoring groups. The results are supported by density functional theory (DFT) calculations, and exhibit a similar behavior to what is observed at alkane-based junctions.
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Affiliation(s)
- Tingwei Gao
- Department of Chemistry, Xi'an-Jiaotong Liverpool University, Suzhou, 215123, China. .,Department of Chemistry, University of Liverpool, Liverpool, L69 7ZD, UK
| | - Chunhui He
- Department of Chemistry, Xi'an-Jiaotong Liverpool University, Suzhou, 215123, China. .,Department of Chemistry, University of Liverpool, Liverpool, L69 7ZD, UK
| | - Chenguang Liu
- Department of Chemistry, Xi'an-Jiaotong Liverpool University, Suzhou, 215123, China.
| | - Yinqi Fan
- Department of Chemistry, Xi'an-Jiaotong Liverpool University, Suzhou, 215123, China. .,Department of Chemistry, University of Liverpool, Liverpool, L69 7ZD, UK
| | - Cezhou Zhao
- Department of Electrical and Electronic Engineering, Xi'an-Jiaotong Liverpool University, Suzhou, 215123, China
| | - Chun Zhao
- Department of Electrical and Electronic Engineering, Xi'an-Jiaotong Liverpool University, Suzhou, 215123, China
| | - Weitao Su
- College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou, 310018, China
| | - Yannick J Dappe
- SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, Gif-sur-Yvette Cedex 91191, France
| | - Li Yang
- Department of Chemistry, Xi'an-Jiaotong Liverpool University, Suzhou, 215123, China. .,Department of Chemistry, University of Liverpool, Liverpool, L69 7ZD, UK
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Prasetio A, Jahandar M, Kim S, Heo J, Kim YH, Lim DC. Mitigating the Undesirable Chemical Reaction between Organic Molecules for Highly Efficient Flexible Organic Photovoltaics. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:2100865. [PMID: 34306987 PMCID: PMC8292892 DOI: 10.1002/advs.202100865] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Indexed: 06/13/2023]
Abstract
Organic photovoltaics (OPVs) with nonfullerene acceptors (NFAs) feature excellent device performance and device stability. However, they are facing problems when the amine-rich polyelectrolytes are used as cathode interfacial layers. In this work, a small molecule, ethanedithiol (EDT) at the polyethyleneimine ethoxylated (PEIE)/active layer interface is inserted for mitigating the undesirable reaction between amine-rich groups and electron-acceptor moieties in NFA. The main role of EDT is to passivate the PEIE surface and prevent electron flow to NFA and the unwanted reaction can be mitigated. It improves the performance of OPV devices by reducing the work function, decreasing trap-assisted recombination, and improving electron-mobility. As a result, the flexible device with the PEIE interfacial layer with a power conversion efficiency (PCE) of 7.20% can be improved to 10.11% after the inclusion of EDT. Moreover, EDT-modified device can retain 98.18% after it is bent for 200 cycles and can maintain 80.83% of its initial PCE under continuous light illuminated in ambient conditions without any encapsulation. Based on these findings, the proposed strategy constitutes a crucial step toward highly efficient flexible OPVs.
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Affiliation(s)
- Adi Prasetio
- Surface Materials DivisionKorea Institute of Materials Science (KIMS)Changwon‐daero 797Changwon51508Republic of Korea
- Department of PhysicsPukyong National UniversityYongso‐ro 45Busan48513Republic of Korea
| | - Muhammad Jahandar
- Surface Materials DivisionKorea Institute of Materials Science (KIMS)Changwon‐daero 797Changwon51508Republic of Korea
| | - Soyeon Kim
- Surface Materials DivisionKorea Institute of Materials Science (KIMS)Changwon‐daero 797Changwon51508Republic of Korea
| | - Jinhee Heo
- Surface Materials DivisionKorea Institute of Materials Science (KIMS)Changwon‐daero 797Changwon51508Republic of Korea
| | - Yong Hyun Kim
- Department of Display EngineeringPukyong National UniversityYongso‐ro 45Busan48513Republic of Korea
| | - Dong Chan Lim
- Surface Materials DivisionKorea Institute of Materials Science (KIMS)Changwon‐daero 797Changwon51508Republic of Korea
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Attenuation Factors in Molecular Electronics: Some Theoretical Concepts. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10186162] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Understanding the electronic transport mechanisms in molecular junctions is of paramount importance to design molecular devices and circuits. In particular, the role of the different junction components contributing to the current decay—namely the attenuation factor—is yet to be clarified. In this short review, we discuss the main theoretical approaches to tackle this question in the non-resonant tunneling regime. We illustrate our purpose through standard symmetric junctions and through recent studies on hybrid molecular junctions using graphene electrodes. In each case, we highlight the contribution from the anchoring groups, the molecular backbone and the electrodes, respectively. In this respect, we consider different anchoring groups and asymmetric junctions. In light of these results, we discuss some perspectives to describe accurately the attenuation factors in molecular electronics.
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