scholarly journals Anchoring Groups Determine Conductance, Thermopower and Thermoelectric Figure of Merit of an Organic Molecular Junction

2021 ◽  
Vol 9 ◽  
Author(s):  
Saeideh Ramezani Akbarabadi ◽  
Mojtaba Madadi Asl
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Electrical Conductance ◽  
Thermal Conductance ◽  
Wide Band ◽  
Transmission Probability ◽  
Molecular Junctions ◽  
Side Group ◽  
Group Position ◽  
Anchoring Groups

Transport properties of molecular junctions are prone to chemical or conformational modifications. Perturbation of the molecule-electrode coupling with anchoring groups or functionalization of the molecule with side groups is a well-characterized method to modulate the thermoelectric properties of molecular junctions. In this study, we used wide-band approximation combined with the non-equilibrium Green’s function (NEGF) formalism to inspect conductance, thermopower and figure of merit of an anthracene molecule coupled to gold (Au) electrodes. To provide a comparative study, three different anchoring groups were used, i.e., thiol, isocyanide and cyanide. The molecule was then perturbed with the amine side group in two positions to explore the interplay between anchoring groups and the side group. We showed that the introduction of side group alters transmission probability near the Fermi energy where transmission peaks are shifted relative to the Fermi level compared to the unperturbed molecule (i.e., without side group), ultimately leading to modified electrical and thermoelectric properties. The greatest value of electrical conductance was achieved when the side-group-perturbed molecule was anchored with isocyanide, whereas the thiol-terminated molecule perturbed with the side group yielded the greatest value of thermal conductance. We found that the Wiedemann-Franz law is violated in the Au-anthracene-Au device. Furthermore, the highest thermopower and figure of merit were attained in the cyanide-terminated perturbed molecule. Our results indicate that charge donating/accepting character of the anchoring group and its interplay with the side group position can modify temperature dependency of conductance, thermopower and figure of merit which is in agreement with experimental findings in organic molecular junctions. Such modifications may potentially contribute to the understanding of emerging conductance-based memory devices designed to mimic the behavior of brain-like synapses.

scholarly journals Side-group-mediated thermoelectric properties of anthracene single-molecule junction with anchoring groups

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Saeideh Ramezani Akbarabadi ◽  
Hamid Rahimpour Soleimani ◽  
Maysam Bagheri Tagani
Keyword(s):  
Thermoelectric Properties ◽  
Single Molecule ◽  
Figure Of Merit ◽  
Density Functional ◽  
Side Group ◽  
Thermoelectric Efficiency ◽  
Group Position ◽  
Single Molecule Junctions ◽  
Molecule Junction ◽  
Anchoring Groups

AbstractCharge transfer characteristics of single-molecule junctions at the nanoscale, and consequently, their thermoelectric properties can be dramatically tuned by chemical or conformational modification of side groups or anchoring groups. In this study, we used density functional theory (DFT) combined with the non-equilibrium Green’s function (NEGF) formalism in the linear response regime to examine the thermoelectric properties of a side-group-mediated anthracene molecule coupled to gold (Au) electrodes via anchoring groups. In order to provide a comparative inspection three different side groups, i.e. amine, nitro and methyl, in two different positions were considered for the functionalization of the molecule terminated with thiol or isocyanide anchoring groups. We showed that when the anchored molecule is perturbed with side group, the peaks of the transmission spectrum were shifted relative to the Fermi energy in comparison to the unperturbed molecule (i.e. without side group) leading to modified thermoelectric properties of the system. Particularly, in the thiol-terminated molecule the amine side group showed the greatest figure of merit in both positions which was suppressed by the change of side group position. However, in the isocyanide-terminated molecule the methyl side group attained the greatest thermoelectric efficiency where its magnitude was relatively robust to the change of side group position. In this way, different combinations of side groups and anchoring groups can improve or suppress thermopower and the figure of merit of the molecular junction depending on the interplay between charge donating/accepting nature of the functionals or their position.

scholarly journals Impurity Substitution Enhances Thermoelectric Figure of Merit in Zigzag Graphene Nanoribbons

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Saeideh Ramezani Akbarabadi ◽  
Mojtaba Madadi Asl
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Density Functional ◽  
Graphene Nanoribbons ◽  
Electrical Conductance ◽  
Thermal Conductance ◽  
Simultaneous Increase ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Zigzag Graphene Nanoribbons

The thermoelectric properties of zigzag graphene nanoribbons (ZGNRs) are sensitive to chemical modification. In this study, we employed density functional theory (DFT) combined with the nonequilibrium green’s function (NEGF) formalism to investigate the thermoelectric properties of a ZGNR system by impurity substitution of single and double nitrogen (N) atoms into the edge of the nanoribbon. N-doping changes the electronic transmission probability near the Fermi energy and suppresses the phononic transmission. This results in a modified electrical conductance, thermal conductance, and thermopower. Ultimately, simultaneous increase of the thermopower and suppression of the electron and phonon contributions to the thermal conductance leads to the significant enhancement of the figure of merit in the perturbed (i.e., doped) system compared to the unperturbed (i.e., nondoped) system. Increasing the number of dopants not only changes the nature of transport and the sign of thermopower but also further suppresses the electron and phonon contributions to the thermal conductance, resulting in an enhanced thermoelectric figure of merit. Our results may be relevant for the development of ZGNR devices with enhanced thermoelectric efficiency.

Thermoelectric properties of B12N12 molecule

2019 ◽  
Vol 16 ◽  
Author(s):  
Mohammad Reza Niazian ◽  
Laleh Farhang Matin ◽  
Mojtaba Yaghobi ◽  
Amir Ali Masoudi
Keyword(s):  
Molecular Electronics ◽  
Thermoelectric Properties ◽  
Electronic Devices ◽  
Thermal Conductance ◽  
Wide Band ◽  
Oscillatory Behavior ◽  
Mapping Technique ◽  
Junction Points ◽  
Inelastic Behaviour ◽  
New Generation

Background: Recently, molecular electronics have attracted the attention of many researchers, both theoretically and applied electronics.Nanostructures have significant thermal properties, which is why they are considered as good options for designing a new generation of integrated electronic devices. Objective: In this paper, the focus is on the thermoelectric properties of the molecular junction points with the electrodes. Also, the influence of the number of atom contacts was investigated on the thermoelectric properties of molecule located between two electrodes metallic.Therefore, the thermoelectric characteristics of the B12 N12 molecule are investigated. Methods: For this purpose, the Green’s function theory as well as mapping technique approach with the wide-band approximation and also the inelastic behaviour is considered for the electron-phonon interactions. Results & Conclusion: Results & Conclusion:It is observed that the largest values of the total part of conductance as well as its elastic (G(e,n)max) depends on the number of atom contacts and are arranged as: G(e,1)max>G(e,4)max>G(e,6)max. Furthermore, the largest values of the electronic thermal conductance, i.e. Kpmax is seen to be in the order of K(p,4)max < K(p,1)max < K(p,6)max that the number of main peaks increases in four-atom contacts at (E<Ef). Furthermore, it is represented that the thermal conductance shows an oscillatory behavior which is significantly affected by the number of atom contacts.

Neural network representation and optimization of thermoelectric states of multiple interacting quantum dots

2020 ◽  
Vol 22 (28) ◽  
pp. 16165-16173
Author(s):  
Hangbo Zhou ◽  
Gang Zhang ◽  
Yong-Wei Zhang
Keyword(s):  
Neural Network ◽  
Machine Learning ◽  
Quantum Dots ◽  
Seebeck Coefficient ◽  
Master Equation ◽  
Thermoelectric Properties ◽  
Electrical Conductance ◽  
Thermal Conductance ◽  
Quantum Master Equation ◽  
Network Representation

We perform quantum master equation calculations and machine learning to investigate the thermoelectric properties of multiple interacting quantum dots, including electrical conductance, Seebeck coefficient, thermal conductance and ZT.

Enhanced thermoelectric properties in nanowires of InAs modulated with multiple-stub structures

2019 ◽  
Vol 9 (5) ◽  
pp. 498-502
Author(s):  
Changning Pan ◽  
Jun He ◽  
Zhiming Liu ◽  
Kaixing Shi
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Thermal Conductance ◽  
Volume Ratio ◽  
Electronic Density ◽  
Energy Filtering ◽  
Carrier Energy ◽  
Inas Nanowires ◽  
Scattering Matrix Method ◽  
Phonon Thermal Conductance

The thermoelectric properties of InAs nanowires modulated with the multiple-stub structures are studied using the scattering-matrix method. Owing to the very large surface-to-volume ratio, both the phonon and electron transport sensitively depend on the geometric structure. Carrier energy filtering which locally distorts electronic density of states strongly enhances the thermopower. Thus optimized thermopower, together with the significant reduction of the phonon thermal conductance, yields the high thermoelectric figure of merit ZT to 0.3∼1.9.

INFLUENCE OF COUPLING GEOMETRY AND DEPHASING ON THERMOELECTRIC PROPERTIES OF A C60 MOLECULAR JUNCTION

NANO ◽  
2014 ◽  
Vol 09 (06) ◽  
pp. 1450057 ◽  
Author(s):  
ZAHRA GOLSANAMLOU ◽  
SAHAR IZADI VISHKAYI ◽  
MEYSAM BAGHERI TAGANI ◽  
HAMID RAHIMPOUR SOLEIMANI
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Tight Binding ◽  
Three Dimensional ◽  
Electrical Conductance ◽  
Interference Effects ◽  
Binding Model ◽  
Contact Points ◽  
Linear Response Regime ◽  
Multiple Contacts

Thermoelectric properties of a C60 molecule coupled to three-dimensional metallic electrodes are studied using Green function formalism in linear response regime. A tight-binding model is used to investigate the effects of the dimerization and coupling geometry on the electrical conductance, thermopower and figure of merit. Increase of the contact points between the molecule and electrodes results in decrease of the number of the peaks of the electrical conductance because of the interference effects. In addition, oscillation of the thermopower is reduced in the multiple contacts. Results show that the increase of the contact points leads to the reduction of the figure of merit. Furthermore, the effect of the phase breaking scattering on the figure of merit is analyzed using the Büttiker probe method.

Influence of multi-sintering on the thermoelectric properties of Bi2Sr2Co2Oy ceramics

2019 ◽  
Vol 34 (02) ◽  
pp. 2050019 ◽  
Author(s):  
Y. Zhang ◽  
M. M. Fan ◽  
C. C. Ruan ◽  
Y. W. Zhang ◽  
X.-J. Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Phonon Scattering ◽  
Sintered Sample ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
The Third ◽  
Ceramic Samples ◽  
Optimum Formula

[Formula: see text] ceramic samples have a structure similar to phonon glass electronic crystals, and their thermoelectric properties can be effectively adjusted through repeated grinding and sintering. The results show that multi-sintering can make their grain refined and increase their grain boundary, which will effectively increase density and phonon scattering. Finally, multi-sintering can reduce the resistivity and thermal conductivity, thus obviously improve thermoelectric figure of merit [Formula: see text] of [Formula: see text]. The optimum [Formula: see text] value of 0.26 is achieved at 923 K by the third sintered sample.

scholarly journals Mechanosynthesis and Thermoelectric Properties of Fe, Zn, and Cd-Doped P-Type Tetrahedrite: Cu12-xMxSb4S13

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3448
Author(s):  
Francisco Arturo López Cota ◽  
José Alonso Díaz-Guillén ◽  
Oscar Juan Dura ◽  
Marco Antonio López de la Torre ◽  
Joelis Rodríguez-Hernández ◽  
...  
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Powder Processing ◽  
High Energy ◽  
Secondary Phases ◽  
Ambient Conditions ◽  
Cadmium Sulfate ◽  
Electrical Conductivities ◽  
Compositional Changes ◽  
P Type

This contribution deals with the mechanochemical synthesis, characterization, and thermoelectric properties of tetrahedrite-based materials, Cu12-xMxSb4S13 (M = Fe2+, Zn2+, Cd2+; x = 0, 1.5, 2). High-energy mechanical milling allows obtaining pristine and substituted tetrahedrites, after short milling under ambient conditions, of stoichiometric mixtures of the corresponding commercially available binary sulfides, i.e., Cu2S, CuS, Sb2S3, and MS (M = Fe2+, Zn2+, Cd2+). All the target materials but those containing Cd were obtained as single-phase products; some admixture of a hydrated cadmium sulfate was also identified by XRD as a by-product when synthesizing Cu10Cd2Sb4S13. The as-obtained products were thermally stable when firing in argon up to a temperature of 350–400 °C. Overall, the substitution of Cu(II) by Fe(II), Zn(II), or Cd(II) reduces tetrahedrites’ thermal and electrical conductivities but increases the Seebeck coefficient. Unfortunately, the values of the thermoelectric figure of merit obtained in this study are in general lower than those found in the literature for similar samples obtained by other powder processing methods; slight compositional changes, undetected secondary phases, and/or deficient sintering might account for some of these discrepancies.

Effects of Ce filling fraction and Fe content on the thermoelectric properties of Co-rich CeyFexCo4−xSb12

2001 ◽  
Vol 16 (3) ◽  
pp. 837-843 ◽  
Author(s):  
Xinfeng Tang ◽  
Lidong Chen ◽  
Takashi Goto ◽  
Toshio Hirai
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Single Phase ◽  
Lattice Thermal Conductivity ◽  
Hole Concentration ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Filling Fraction ◽  
Fe Content

Single-phase filled skutterudite compounds, CeyFexCo4−xSb12 (x = 0 to 3.0, y = 0 to 0.74), were synthesized by a melting method. The effects of Fe content and Ce filling fraction on the thermoelectric properties of CeyFexCo4−xSb12 were investigated. The lattice thermal conductivity of Ce-saturated CeyFexCo4−xSb12, y being at the maximum corresponding to x, decreased with increasing Fe content (x) and reached its minimum at about x = 1.5. When x was 1.5, lattice thermal conductivity decreased with increasing Ce filling fraction till y = 0.3 and then began to increase after reaching the minimum at y = 0.3. Hole concentration and electrical conductivity of Cey Fe1.5Co2.5Sb12 decreased with increasing Ce filling fraction. The Seebeck coefficient increased with increasing Ce filling fraction. The greatest dimensionless thermoelectric figure of merit T value of 1.1 was obtained at 750 K for the composition of Ce0.28Fe1.52Co2.48Sb12.

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