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Alotaibi T, Alshahrani M, Alshammari M, Alotaibi M, Taha TAM, Al-Jobory AA, Ismael A. Orientational Effects and Molecular-Scale Thermoelectricity Control. ACS OMEGA 2024; 9:29537-29543. [PMID: 39005829 PMCID: PMC11238236 DOI: 10.1021/acsomega.4c02141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 06/10/2024] [Accepted: 06/12/2024] [Indexed: 07/16/2024]
Abstract
The orientational effect concept in a molecular-scale junction is established for asymmetric junctions, which requires the fulfillment of two conditions: (1) design of an asymmetric molecule with strong distinct terminal end groups and (2) construction of a doubly asymmetric junction by placing an asymmetric molecule in an asymmetric junction to form a multicomponent system such as Au/Zn-TPP+M/Au. Here, we demonstrate that molecular-scale junctions that satisfy the conditions of these effects can manifest Seebeck coefficients whose sign fluctuates depending on the orientation of the molecule within the asymmetric junction in a complete theoretical investigation. Three anthracene-based compounds are investigated in three different scenarios, one of which displays a bithermoelectric behavior due to the presence of strong anchor groups, including pyridyl and thioacetate. This bithermoelectricity demonstration implies that if molecules with alternating orientations can be placed between an asymmetric source and drain, they can be potentially utilized for increasing the thermovoltage in molecular-scale thermoelectric energy generators (TEGs).
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Affiliation(s)
- Turki Alotaibi
- Department
of Physics, College of Science, Jouf University, Sakaka 72388, Saudi Arabia
| | - Maryam Alshahrani
- Department
of Physics, College of Science, University
of Bisha, P.O. Box 551, Bisha 61922, Saudi Arabia
| | - Majed Alshammari
- Department
of Physics, College of Science, Jouf University, Sakaka 72388, Saudi Arabia
| | - Moteb Alotaibi
- Department
of Physics, College of Science and Humanities in Al-Kharj, Prince Sattam bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
| | - Taha Abdel Mohaymen Taha
- Physics
and Engineering Mathematics Department, Faculty of Electronic Engineering, Menoufia University, Menouf 32952, Egypt
| | - Alaa A. Al-Jobory
- Department
of Physics, College of Science, University
of Anbar, Anbar 31001, Iraq
| | - Ali Ismael
- Department
of Physics, Lancaster University, Lancaster LA1 4YB, U.K.
- Department
of Physics, College of Education for Pure Science, Tikrit University, Tikrit 3400, Iraq
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2
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Ismael AK, Al-Jobory A. Energy gap and aromatic molecular rings. ROYAL SOCIETY OPEN SCIENCE 2024; 11:231533. [PMID: 38577212 PMCID: PMC10987978 DOI: 10.1098/rsos.231533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 02/04/2024] [Accepted: 02/13/2024] [Indexed: 04/06/2024]
Abstract
The manuscript combines rational density functional theory simulations and experimental data to investigate the electrical properties of eight polycyclic aromatic hydrocarbons (PAHs). The optimized geometries reveal a preference for one-row, two-row and three-row ring distributions. Band structure plots demonstrate an inverse correlation between the number of aromatic rings and band gap size, with a specific order observed across the PAHs. Gas phase simulations support these findings, though differences in values are noted compared to the literature. Introducing a two-row ring distribution concept resolves discrepancies, particularly in azulene. The B3LYP function successfully bridges theoretical and experimental gaps, particularly in large PAHs. The manuscript highlights the potential for designing electronic devices based on different-sized PAHs, emphasizing a multi-ring distribution approach and opening new avenues for practical applications.
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Affiliation(s)
- Ali K. Ismael
- Department of Physics, Lancaster University, LancasterLA1 4YB, UK
- Department of Physics, College of Education for Pure Science, Tikrit University, Tikrit, Salah Al Deen34001, Iraq
| | - Alaa Al-Jobory
- Department of Physics, Lancaster University, LancasterLA1 4YB, UK
- Department of Physics, College of Science, University of Anbar, Al Rumadi, Al Anbar31001, Iraq
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3
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Ismael AK. 20-State Molecular Switch in a Li@C 60 Complex. ACS OMEGA 2023; 8:19767-19771. [PMID: 37305247 PMCID: PMC10249121 DOI: 10.1021/acsomega.3c01455] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 05/16/2023] [Indexed: 06/13/2023]
Abstract
A substantial potential advantage of industrial electric and thermoelectric devices utilizing endohedral metallofullerenes (EMFs) is their ability to accommodate metallic moieties inside their empty cavities. Experimental and theoretical studies have elucidated the merit of this extraordinary feature with respect to developing electrical conductance and thermopower. Published research studies have demonstrated multiple state molecular switches initiated with 4, 6, and 14 distinguished switching states. Through comprehensive theoretical investigations involving electronic structure and electric transport, we report 20 molecular switching states that can be statistically recognized employing the endohedral fullerene Li@C60 complex. We propose a switching technique that counts on the location of the alkali metal that encapsulates inside a fullerene cage. The 20 switching states correspond to the 20 hexagonal rings that the Li cation energetically prefers to reside close to. We demonstrate that the multiswitching feature of such molecular complexes can be controlled by taking advantage of the off-center displacement and charge transfer from the alkali metal to the C60 cage. The most energetically favorable optimization suggests 1.2-1.4 Å off-center displacement, and Mulliken, Hirshfeld, and Voronoi simulations articulate that the charge migrates from the Li cation to C60 fullerene; however, the amount of the charge transferred depends on the nature and location of the cation within the complex. We believe that the proposed work suggests a relevant step toward the practical application of molecular switches in organic materials.
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Affiliation(s)
- Ali K. Ismael
- Department
of Physics, Lancaster University, Lancaster LA1 4YB, U.K.
- Department
of Physics, College of Education for Pure Science, Tikrit University, Salahuddin, Al-Qadissiya street 34001, Tikrit, Iraq
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4
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Eryilmaz IH, Chen YF, Mattana G, Orgiu E. Organic thermoelectric generators: working principles, materials, and fabrication techniques. Chem Commun (Camb) 2023; 59:3160-3174. [PMID: 36805573 DOI: 10.1039/d2cc04205c] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
Organic thermoelectricity is a blooming field of research that employs organic (semi)conductors to recycle waste heat through its partial conversion to electrical power. Such a conversion occurs by means of organic thermoelectric generator (OTEG) devices. The recent process on the synthesis of novel materials and on the understanding of doping mechanisms to increase conductivity has tremendously narrowed the gap between laboratory research and their application in actual applications. This Feature Article intends to highlight the impressive progress in materials and fabrication techniques for OTEGs made in recent years.
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Affiliation(s)
- Ilknur Hatice Eryilmaz
- Institut national de la recherche scientifique, Centre Énergie Matériaux Télécommunications, 1650 Blvd. Lionel-Boulet, J3X 1P7, Varennes, QC, Canada.
| | - Yan-Fang Chen
- Institut national de la recherche scientifique, Centre Énergie Matériaux Télécommunications, 1650 Blvd. Lionel-Boulet, J3X 1P7, Varennes, QC, Canada.
| | - Giorgio Mattana
- Université Paris Cité, ITODYS, CNRS, UMR 7086, 15 rue J.-A. de Baïf, F-75013 Paris, France.
| | - Emanuele Orgiu
- Institut national de la recherche scientifique, Centre Énergie Matériaux Télécommunications, 1650 Blvd. Lionel-Boulet, J3X 1P7, Varennes, QC, Canada.
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5
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Alshehab A, Ismael AK. Impact of the terminal end-group on the electrical conductance in alkane linear chains. RSC Adv 2023; 13:5869-5873. [PMID: 36816091 PMCID: PMC9936266 DOI: 10.1039/d3ra00019b] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Accepted: 02/13/2023] [Indexed: 02/19/2023] Open
Abstract
This research presents comprehensive theoretical investigations of a series of alkane-based chains using four different terminal end groups including amine -NH2, thiomethyl -SMe, thiol -SH and direct carbon contact -C. It is widely known that the electrical conductance of single molecules can be tuned and boosted by chemically varying their terminal groups to metal electrodes. Here, we demonstrate how different terminal groups affect alkane molecules' electrical conductance. In general, alkane chain conductance decreases exponentially with length, regardless of the anchor group types. In these simulations the molecular length varies from 3 to 8 -CH2 units, with 4 different linker groups; these simulations suggest that the conductances follow the order G C > G SH > G SMe > G NH2 . The DFT prediction order of the 4 anchors is well supported by STM measurements. This work demonstrates an excellent correlation between our simulations and experimental measurements, namely: the percent difference ΔG, exponential decay slopes, A constants and β factors at different molecular alkane chain lengths.
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Affiliation(s)
- Abdullah Alshehab
- Physics Department, College of Science, King Faisal UniversityAl AhsaSaudi Arabia
| | - Ali K. Ismael
- Department of Physics, Lancaster UniversityLancaster LA1 4YBUK
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6
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Alshammari M, Al-Jobory AA, Alotaibi T, Lambert CJ, Ismael A. Orientational control of molecular scale thermoelectricity. NANOSCALE ADVANCES 2022; 4:4635-4638. [PMID: 36341305 PMCID: PMC9595198 DOI: 10.1039/d2na00515h] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 10/03/2022] [Indexed: 06/13/2023]
Abstract
Through a comprehensive theoretical study, we demonstrate that single-molecule junctions formed from asymmetric molecules with different terminal groups can exhibit Seebeck coefficients, whose sign depends on the orientation of the molecule within the junction. Three anthracene-based molecules are studied, one of which exhibits this bi-thermoelectric behaviour, due to the presence of a thioacetate terminal group at one end and a pyridyl terminal group at the other. A pre-requisite for obtaining this behaviour is the use of junction electrodes formed from different materials. In our case, we use gold as the bottom electrode and graphene-coated gold as the top electrode. This demonstration of bi-thermoelecricity means that if molecules with alternating orientations can be deposited on a substrate, then they form a basis for boosting the thermovoltage in molecular-scale thermoelectric energy generators (TEGs).
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Affiliation(s)
- Majed Alshammari
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Science, Jouf University Sakaka Saudi Arabia
| | - Alaa A Al-Jobory
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Science, University of Anbar Anbar Iraq
| | - Turki Alotaibi
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Science, Jouf University Sakaka Saudi Arabia
| | - Colin J Lambert
- Physics Department, Lancaster University Lancaster LA1 4YB UK
| | - Ali Ismael
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Education for Pure Science, Tikrit University Tikrit Iraq
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7
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Wang X, Ismael A, Ning S, Althobaiti H, Al-Jobory A, Girovsky J, Astier HPAG, O'Driscoll LJ, Bryce MR, Lambert CJ, Ford CJB. Electrostatic Fermi level tuning in large-scale self-assembled monolayers of oligo(phenylene-ethynylene) derivatives. NANOSCALE HORIZONS 2022; 7:1201-1209. [PMID: 35913108 DOI: 10.1039/d2nh00241h] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Understanding and controlling the orbital alignment of molecules placed between electrodes is essential in the design of practically-applicable molecular and nanoscale electronic devices. The orbital alignment is highly determined by the molecule-electrode interface. Dependence of orbital alignment on the molecular anchor group for single molecular junctions has been intensively studied; however, when scaling-up single molecules to large parallel molecular arrays (like self-assembled monolayers (SAMs)), two challenges need to be addressed: 1. Most desired anchor groups do not form high quality SAMs. 2. It is much harder to tune the frontier molecular orbitals via a gate voltage in SAM junctions than in single molecular junctions. In this work, we studied the effect of the molecule-electrode interface in SAMs with a micro-pore device, using a recently developed tetrapodal anchor to overcome challenge 1, and the combination of a single layered graphene top electrode with an ionic liquid gate to solve challenge 2. The zero-bias orbital alignment of different molecules was signalled by a shift in conductance minimum vs. gate voltage for molecules with different anchoring groups. Molecules with the same backbone, but a different molecule-electrode interface, were shown experimentally to have conductances that differ by a factor of 5 near zero bias. Theoretical calculations using density functional theory support the trends observed in the experimental data. This work sheds light on how to control electron transport within the HOMO-LUMO energy gap in molecular junctions and will be applicable in scaling up molecular electronic systems for future device applications.
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Affiliation(s)
- Xintai Wang
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
- School of Information Science and Technology, Dalian Maritime University, Dalian, China
| | - Ali Ismael
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK.
- Department of Physics, College of Education for Pure Science, Tikrit University, Tikrit, Iraq
| | - Shanglong Ning
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Hanan Althobaiti
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK.
- Department of Physics, College of Science, Taif-University, Taif, Saudi Arabia
| | - Alaa Al-Jobory
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK.
- Department of Physics, College of Science, University of Anbar, Anbar, Iraq
| | - Jan Girovsky
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Hippolyte P A G Astier
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Luke J O'Driscoll
- Department of Chemistry, Durham University, Lower Mountjoy, Stockton Road, Durham, DH1 3LE, UK
| | - Martin R Bryce
- Department of Chemistry, Durham University, Lower Mountjoy, Stockton Road, Durham, DH1 3LE, UK
| | - Colin J Lambert
- Physics Department, Lancaster University, Lancaster, LA1 4YB, UK.
| | - Christopher J B Ford
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
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8
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Ismael AK, Rincón-García L, Evangeli C, Dallas P, Alotaibi T, Al-Jobory AA, Rubio-Bollinger G, Porfyrakis K, Agraït N, Lambert CJ. Exploring seebeck-coefficient fluctuations in endohedral-fullerene, single-molecule junctions. NANOSCALE HORIZONS 2022; 7:616-625. [PMID: 35439804 DOI: 10.1039/d1nh00527h] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
For the purpose of creating single-molecule junctions, which can convert a temperature difference ΔT into a voltage ΔV via the Seebeck effect, it is of interest to screen molecules for their potential to deliver high values of the Seebeck coefficient S = -ΔV/ΔT. Here we demonstrate that insight into molecular-scale thermoelectricity can be obtained by examining the widths and extreme values of Seebeck histograms. Using a combination of experimental scanning-tunnelling-microscopy-based transport measurements and density-functional-theory-based transport calculations, we study the electrical conductance and Seebeck coefficient of three endohedral metallofullerenes (EMFs) Sc3N@C80, Sc3C2@C80, and Er3N@C80, which based on their structures, are selected to exhibit different degrees of charge inhomogeneity and geometrical disorder within a junction. We demonstrate that standard deviations in the Seebeck coefficient σS of EMF-based junctions are correlated with the geometric standard deviation σ and the charge inhomogeneity σq. We benchmark these molecules against C60 and demonstrate that both σq, σS are the largest for Sc3C2@C80, both are the smallest for C60 and for the other EMFs, they follow the order Sc3C2@C80 > Sc3N@C80 > Er3N@C80 > C60. A large value of σS is a sign that a molecule can exhibit a wide range of Seebeck coefficients, which means that if orientations corresponding to high values can be selected and controlled, then the molecule has the potential to exhibit high-performance thermoelectricity. For the EMFs studied here, large values of σS are associated with distributions of Seebeck coefficients containing both positive and negative signs, which reveals that all these EMFs are bi-thermoelectric materials.
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Affiliation(s)
- Ali K Ismael
- Department of Physics, Lancaster University, Lancaster, UK.
- Department of Physics, College of Education for Pure Science, Tikrit University, Tikrit, Iraq
| | - Laura Rincón-García
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | | | - Panagiotis Dallas
- Institute of Nanoscience and Nanotechnology, NCSR Demokritos, 15310 Athens, Greece
- Department of Materials, University of Oxford, OX1 3PH, UK
| | - Turki Alotaibi
- Department of Physics, Lancaster University, Lancaster, UK.
- Department of Physics, College of Science, Jouf University, Sakaka, Saudi Arabia
| | - Alaa A Al-Jobory
- Department of Physics, Lancaster University, Lancaster, UK.
- Department of Physics, College of Science, University of Anbar, Anbar, Iraq
| | - Gabino Rubio-Bollinger
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Condensed Matter Physics Center (IFIMAC) and Instituto Universitario de Ciencia de Materiales "Nicolás Cabrera" (INC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
| | - Kyriakos Porfyrakis
- Department of Materials, University of Oxford, OX1 3PH, UK
- Faculty of Engineering and Science, University of Greenwich, Central Avenue, Chatham Maritime, ME4 4TB, UK
| | - Nicolás Agraït
- Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Condensed Matter Physics Center (IFIMAC) and Instituto Universitario de Ciencia de Materiales "Nicolás Cabrera" (INC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
- Fundación IMDEA Nanociencia, Calle Faraday 9, Campus Universitario de Cantoblanco, E-28049 Madrid, Spain
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9
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Bennett TLR, Alshammari M, Au-Yong S, Almutlg A, Wang X, Wilkinson LA, Albrecht T, Jarvis SP, Cohen LF, Ismael A, Lambert CJ, Robinson BJ, Long NJ. Multi-component self-assembled molecular-electronic films: towards new high-performance thermoelectric systems. Chem Sci 2022; 13:5176-5185. [PMID: 35655580 PMCID: PMC9093172 DOI: 10.1039/d2sc00078d] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 04/14/2022] [Indexed: 12/02/2022] Open
Abstract
The thermoelectric properties of parallel arrays of organic molecules on a surface offer the potential for large-area, flexible, solution processed, energy harvesting thin-films, whose room-temperature transport properties are controlled by quantum interference (QI). Recently, it has been demonstrated that constructive QI (CQI) can be translated from single molecules to self-assembled monolayers (SAMs), boosting both electrical conductivities and Seebeck coefficients. However, these CQI-enhanced systems are limited by rigid coupling of the component molecules to metallic electrodes, preventing the introduction of additional layers which would be advantageous for their further development. These rigid couplings also limit our ability to suppress the transport of phonons through these systems, which could act to boost their thermoelectric output, without comprising on their impressive electronic features. Here, through a combined experimental and theoretical study, we show that cross-plane thermoelectricity in SAMs can be enhanced by incorporating extra molecular layers. We utilize a bottom-up approach to assemble multi-component thin-films that combine a rigid, highly conductive 'sticky'-linker, formed from alkynyl-functionalised anthracenes, and a 'slippery'-linker consisting of a functionalized metalloporphyrin. Starting from an anthracene-based SAM, we demonstrate that subsequent addition of either a porphyrin layer or a graphene layer increases the Seebeck coefficient, and addition of both porphyrin and graphene leads to a further boost in their Seebeck coefficients. This demonstration of Seebeck-enhanced multi-component SAMs is the first of its kind and presents a new strategy towards the design of thin-film thermoelectric materials.
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Affiliation(s)
- Troy L R Bennett
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
| | - Majed Alshammari
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Science, Jouf University Skaka Saudi Arabia
| | - Sophie Au-Yong
- Physics Department, Lancaster University Lancaster LA1 4YB UK
| | - Ahmad Almutlg
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Mathematics, College of Science, Qassim University Almethnab Saudi Arabia
| | - Xintai Wang
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- The Blackett Laboratory, Imperial College London, South Kensington Campus London SW7 2AZ UK
| | - Luke A Wilkinson
- Department of Chemistry, University of York Heslington York YO10 5DD UK
| | - Tim Albrecht
- Department of Chemistry, Birmingham University Edgbaston Birmingham B15 2TT UK
| | - Samuel P Jarvis
- Physics Department, Lancaster University Lancaster LA1 4YB UK
| | - Lesley F Cohen
- The Blackett Laboratory, Imperial College London, South Kensington Campus London SW7 2AZ UK
| | - Ali Ismael
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Education for Pure Science, Tikrit University Tikrit Iraq
| | - Colin J Lambert
- Physics Department, Lancaster University Lancaster LA1 4YB UK
| | | | - Nicholas J Long
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
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10
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Wang X, Ismael A, Almutlg A, Alshammari M, Al-Jobory A, Alshehab A, Bennett TLR, Wilkinson LA, Cohen LF, Long NJ, Robinson BJ, Lambert C. Optimised power harvesting by controlling the pressure applied to molecular junctions. Chem Sci 2021; 12:5230-5235. [PMID: 34163759 PMCID: PMC8179551 DOI: 10.1039/d1sc00672j] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 02/22/2021] [Indexed: 11/21/2022] Open
Abstract
A major potential advantage of creating thermoelectric devices using self-assembled molecular layers is their mechanical flexibility. Previous reports have discussed the advantage of this flexibility from the perspective of facile skin attachment and the ability to avoid mechanical deformation. In this work, we demonstrate that the thermoelectric properties of such molecular devices can be controlled by taking advantage of their mechanical flexibility. The thermoelectric properties of self-assembled monolayers (SAMs) fabricated from thiol terminated molecules were measured with a modified AFM system, and the conformation of the SAMs was controlled by regulating the loading force between the organic thin film and the probe, which changes the tilt angle at the metal-molecule interface. We tracked the thermopower shift vs. the tilt angle of the SAM and showed that changes in both the electrical conductivity and Seebeck coefficient combine to optimize the power factor at a specific angle. This optimization of thermoelectric performance via applied pressure is confirmed through the use of theoretical calculations and is expected to be a general method for optimising the power factor of SAMs.
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Affiliation(s)
- Xintai Wang
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- The Blackett Laboratory, Imperial College London, South Kensington Campus London SW7 2AZ UK
| | - Ali Ismael
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Education for Pure Science, Tikrit University Tikrit Iraq
| | - Ahmad Almutlg
- Physics Department, Lancaster University Lancaster LA1 4YB UK
| | | | - Alaa Al-Jobory
- Physics Department, Lancaster University Lancaster LA1 4YB UK
- Department of Physics, College of Science, University of Anbar Anbar Iraq
| | | | - Troy L R Bennett
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
| | - Luke A Wilkinson
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
- Department of Chemistry, University of York Heslington York YO10 5DD UK
| | - Lesley F Cohen
- The Blackett Laboratory, Imperial College London, South Kensington Campus London SW7 2AZ UK
| | - Nicholas J Long
- Department of Chemistry, Imperial College London, MSRH White City London W12 0BZ UK
| | | | - Colin Lambert
- Physics Department, Lancaster University Lancaster LA1 4YB UK
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