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Electron transport phenomenon simulation through the carborane nano-molecular wire
, Article Physica E: Low-dimensional Systems and Nanostructures ; Volume 40, Issue 9 , August , 2008 , Pages 2965–2972 ; Non-Equilibrium Green's function ; Gholami, M. R. (Mohammad Reza) ; Monajjemi, M ; Ganji, M. D ; Sharif University of Technology
Abstract
The electron transport characteristics of a 1,10-dimethylene-1,10-dicarba-closo-decaborane (10-vertex carborane) single molecular conductor is investigated via the density functional-based non-equilibrium Green's function (DFT-NEGF) method. We consider three configurations for the molecular wire sandwiched between two Au(1 0 0) electrodes: the hollow site, top site and bridge site positions. Our results show that the energetically favorable hollow site configuration has a higher current intensity than the other configurations. The projection of the density of states (PDOS) and the transmission coefficients T(E) of the two-probe system at zero bias are analyzed, and it suggests that the...
Recent developments in dye-sensitized solar cells
, Article ChemPhysChem ; Vol. 15, issue. 18 , Dec , 2014 , p. 3902-3927 ; Tajabadi, F ; Taghavinia, N ; Sharif University of Technology
Abstract
The knowledge of dye-sensitized solar cells (DSCs) has expanded considerably in recent years. They are multiparameter and complex systems that work only if various parameters are tuned simultaneously. This makes it difficult to target to a single parameter to improve the efficiency. There is a wealth of knowledge concerning different DSC structures and characteristics. In this review, the present knowledge and recent achievements are surveyed with emphasis on the more promising cell materials and designs
Dissipative vibrational model for chiral recognition in olfaction
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 92, Issue 3 , 2015 ; 15393755 (ISSN) ; Taher Ghahramani, F ; Shafiee, A ; Sharif University of Technology
American Physical Society
2015
Abstract
We examine the olfactory discrimination of left- and right-handed enantiomers of chiral odorants based on the odorant-mediated electron transport from a donor to an acceptor of the olfactory receptors embodied in a biological environment. The chiral odorant is effectively described by an asymmetric double-well potential whose minima are associated to the left- and right-handed enantiomers. The introduced asymmetry is considered an overall measure of chiral interactions. The biological environment is conveniently modeled as a bath of harmonic oscillators. The resulting spin-boson model is adapted by a polaron transformation to derive the corresponding Born-Markov master equation with which we...
Design of nanoswitch based on C20-bowl molecules: A first principles study
, Article Microelectronics Journal ; Volume 39, Issue 12 , December , 2008 , Pages 1499–1503 ; Aghaei, H ; Gholami, M. R. (Mohammad Reza) ; Sharif University of Technology
Abstract
We demonstrate theoretically by density functional non-equilibrium Green's function method that a much simplest two-terminal wire can exhibit switching, and we present a realistic theory of its behavior. We consider a C20-bowl molecular wire sandwiched between an Au (1 0 0) substrate and a monatomic Au scanning tunneling microscope (STM) tip. Lateral motion of the tip over the pentagon ring causes it to change from one conformation class to the other and to switch between a strongly and a weakly conducting state. Thus, surprisingly, despite their apparent simplicity, these Au/C20/Au nanowires are shown to be a convenient switch, the simplest two-terminal molecular switches to date....
Theoretical study of the electron transport through the cysteine amino acid nanomolecular wire
, Article International Journal of Nanoscience ; Volume 07, Issue 02, n 03 , April & June , 2008 , pp. 95-102 ; Aghaie, H ; Gholami, M. R.(Mohammad Reza) ; Sharif University of Technology
Abstract
In this paper, we study the electrical transport and Negative Differential Resistance (NDR) in a single molecular conductor consisting of a cysteine sandwiched between two Au(111) electrodes via the Density Functional Theory-based Nonequilibrium Green's Function (DFT-NEGF) method. We show that (surprisingly, despite their apparent simplicity, these Au/cysteine/Au nanowires are shown to be a convenient NDR device) the smallest two-terminal molecular wire can exhibit NDR behavior to date. Experiments with a conventional or novel self-assembled monolayer (SAM) are proposed to test these predictions. The projected density of states (PDOSs) and transmission coefficients T(E) under various...
Nanosheet arrays of TiO2synthesized by one step conversion of ZnO nanosheets: Boosting of electron transport rate and application in dye solar cells
, Article RSC Advances ; Vol. 4, issue. 85 , 2014 , pp. 45174-45179 ; ISSN: 20462069 ; Tajabadi, F ; Salehkoutahi, S. M ; Ghahary, R ; Taghavinia, N ; Sharif University of Technology
Abstract
A TiO2replica of ZnO nanosheet films is synthesized using a chemical replacement process. ZnO nanosheets are grown by electrodeposition on fluorine doped tin oxide (FTO) films, and a dissolution/deposition process is used to convert the ZnO template into a TiO2replica. Electron microscopy shows the final TiO2structure follows the morphology of the initial ZnO template. X-ray diffraction and energy dispersive spectroscopy verify the total transformation of ZnO to TiO2. The as-synthesized TiO2sheets are amorphous and after annealing turn into the anatase phase. The film of TiO2nanosheets is used as the photoanode of a dye sensitized solar cell. Despite the low roughness factor of 100, a...
The synergistic effect of dimethyl sulfoxide vapor treatment and C60 electron transporting layer towards enhancing current collection in mixed-ion inverted perovskite solar cells
, Article Journal of Power Sources ; Volume 405 , 2018 , Pages 70-79 ; 03787753 (ISSN) ; Aitola, K ; Sveinbjörnsson, K ; Yang, W ; Svanström, S ; Cappel, U. B ; Rensmo, H ; Johansson, E. M. J ; Taghavinia, N ; Boschloo, G ; Sharif University of Technology
Elsevier B.V
2018
Abstract
Inverted perovskite solar cells (PSCs) have been introduced as better candidate for roll-to-roll printing and scale-up than their conventional configuration counterparts, while their fabrication is technically more demanding. The common light absorbing layer in inverted PSCs is the single cation methylammonium lead iodide (MAPbI3) perovskite, whereas mixed-ion perovskites are chemically more stable. In mixed-ion perovskites, where FA (formamidinium) is the main replacement for MA, the electron affinity is larger than in MAPbI3 perovskites, leading to possible barriers against photoelectron collection by the electron transporting layer (ETL). In this paper we report on a mixed-ion...
Improvement of planar perovskite solar cells by using solution processed SnO2/CdS as electron transport layer
, Article Solar Energy ; Volume 191 , 2019 , Pages 647-653 ; 0038092X (ISSN) ; Javadpour, S ; Taghavinia, N ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
The efficiency of planar perovskite solar cells (PSCs) with SnO2 as electron transport layer is already more than 19% achieved under controlled atmosphere. PSCs with solution processed SnO2 show high hysteresis and low fill factor. One way to improve the planar PSCs is using buffer layer between electron transport layer and perovskite to enhance the photo-electron extraction process. In this study, SnO2 and SnO2/CdS layers were fabricated by solution process using a suspension including CdS nanoparticles synthesized via a simple solution route. Then planar PSCs with the structure of Glass/FTO/ETL/Perovskite/Sprio-OMeTAD/Au were fabricated in ambient air condition using SnO2 and SnO2/CdS as...
The effect of structural defects on the electron transport of MoS 2 nanoribbons based on density functional theory
, Article Journal of Theoretical and Applied Physics ; Volume 13, Issue 1 , 2019 , Pages 55-62 ; 22517227 (ISSN) ; Fathipour, M ; Faez, R ; Darvish, G ; Sharif University of Technology
SpringerOpen
2019
Abstract
Using non-equilibrium Green’s function method and density functional theory, we study the effect of line structural defects on the electron transport of zigzag molybdenum disulfide (MoS 2 ) nanoribbons. Here, the various types of non-stoichiometric line defects greatly affect the electron conductance of MoS 2 nanoribbons. Although such defects would be lead to the electron scattering, they can increase the transmission of charge carriers by creating new channels. In addition, the presence of S bridge defect in the zigzag MoS 2 nanoribbon leads to more the transmission of charge carriers in comparison with the Mo–Mo bond defect. Also, we find that the different atomic orbitals and their...
Improving the performance of planar perovskite solar cell using NH4Cl treatment of SnO2 as electron transport layer
, Article Surfaces and Interfaces ; 2021 ; 24680230 (ISSN) ; Zamani Meymian, M. R ; Taghavinia, N ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Here in this research, a modified interface between the electron transport layer (ETL) and the perovskite layer in a perovskite solar cell (PSC) is provided by adding the ammonium chloride (NH4Cl) to the tin oxide (SnO2) as the modified ETL of a planar structure as follows: fluorine-doped tin oxide (FTO)/NH4Cl-SnO2/Mixed cation perovskite/Copper indium disulfide (CIS)/Gold (Au). The effects of NH4Cl on ETL are investigated in different amounts from 0.003 to 0.02 M and the best results were obtained in the amount of 0.013 M. The best NH4Cl-SnO2 ETL could increase the power conversion efficiency (PCE) of fabricated planar PSC by 16.79% with open-circuit voltage (Voc) of 1.15 V and negligible...
Temperature and voltage dependence of magnetic barrier junctions with a nonmagnetic spacer
, Article European Physical Journal B ; Volume 42, Issue 2 , 2004 , Pages 187-191 ; 14346028 (ISSN) ; Saffarzadeh, A ; Sharif University of Technology
2004
Abstract
The temperature and voltage dependence of spin transport is theoretically investigated in a new type of magnetic tunnel junction, which consists of two ferromagnetic outer electrodes separated by a ferromagnetic barrier and a nonmagnetic (NM) metallic spacer. The effect of spin fluctuation in magnetic barrier, which plays an important role at finite temperature, is included by taking the mean-field approximation. It is found that, the tunnel magnetoresistance (TMR) and the electron-spin polarization depend strongly on the temperature and the applied voltage. The TMR and spin polarization at different temperatures show an oscillatory behavior as a function of the NM spacer thickness. Also,...
Improving the performance of planar perovskite solar cell using NH4Cl treatment of SnO2 as electron transport layer
, Article Surfaces and Interfaces ; Volume 28 , 2022 ; 24680230 (ISSN) ; Zamani Meymian, M. R ; Taghavinia, N ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Here in this research, a modified interface between the electron transport layer (ETL) and the perovskite layer in a perovskite solar cell (PSC) is provided by adding the ammonium chloride (NH4Cl) to the tin oxide (SnO2) as the modified ETL of a planar structure as follows: fluorine-doped tin oxide (FTO)/NH4Cl-SnO2/Mixed cation perovskite/Copper indium disulfide (CIS)/Gold (Au). The effects of NH4Cl on ETL are investigated in different amounts from 0.003 to 0.02 M and the best results were obtained in the amount of 0.013 M. The best NH4Cl-SnO2 ETL could increase the power conversion efficiency (PCE) of fabricated planar PSC by 16.79% with open-circuit voltage (Voc) of 1.15 V and negligible...
Development of an aqueous TiO2 paste in terms of morphological manipulation of nanostructured photoanode electrode of dye-sensitized solar cells
,
Article
Journal of Sol-Gel Science and Technology
;
Volume 75, Issue 2
,
August
,
2015
,
Pages 447-459
;
09280707 (ISSN)
; Mohammadi, M. R
;
Sharif University of Technology
Kluwer Academic Publishers
2015
Abstract
Abstract: A novel simple synthetic procedure for improving cell efficiency and reducing the production cost of TiO2 dye-sensitized solar cells (DSSCs) by modification and optimization of homemade formulated paste is reported. This is achieved in terms of morphological manipulation of deposited monolayer TiO2 films by controlling three processing parameters of paste formulation. These parameters are tailored to obtain a paste with proper viscosity suitable for spin-coating technique and to achieve uniform, homogeneous, and crack-free films with good connections between TiO2 grains and porous structure. Photovoltaic measurements show that TiO2 ...
Effect of a gap opening on the conductance of graphene superlattices
, Article Solid State Communications ; Volume 150, Issue 13-14 , 2010 , Pages 655-659 ; 00381098 (ISSN) ; Esmailpour, A ; Asgari, R ; Elahi, M ; Rahimi Tabar, M. R ; Sharif University of Technology
2010
Abstract
The electronic transmission and conductance of a gapped graphene superlattice were calculated by means of the transfer-matrix method. The system that we study consists of a sequence of electron-doped graphene as wells and hole-doped graphene as barriers. We show that the transmission probability approaches unity at some critical value of the gap. We also find that there is a domain around the critical gap value for which the conductance of the system attains its maximum value
Trap density measurement in three-dimensional nanostructured photoelectrode of titanium dioxide with various morphologies
, Article Applied Physics A: Materials Science and Processing ; Volume 122, Issue 4 , 2016 ; 09478396 (ISSN) ; Mohammadpour, R ; Sharif University of Technology
Springer Verlag
2016
Abstract
Three-dimensional TiO2 nanostructures take advantages of large surface area and superior light-harvesting efficiency, as well as appropriate charge carrier transport and separation features. Here in this research, we report for the first time on measurement of density of localized trap states in three-dimensional TiO2 nanostructures with various morphologies. Bare 1-dimensional TiO2 nanofibers have been synthesized via two different methods: electrospinning and hydrothermal processes. The surface of TiO2 nanofibrous has been modified with nanoparticles and nanobranches thorough second hydrothermal process. Various morphologies of nanostructured TiO2 have been fabricated including...
Theoretical study of the electron transport through the cysteine amino acid nanomolecular wire
, Article International Journal of Nanoscience ; Volume 7, Issue 2-3 , 2008 , Pages 95-102 ; 0219581X (ISSN) ; Aghaie, H ; Gholami, M. R ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2008
Abstract
In this paper, we study the electrical transport and Negative Differential Resistance (NDR) in a single molecular conductor consisting of a cysteine sandwiched between two Au(111) electrodes via the Density Functional Theory-based Nonequilibrium Green's Function (DFT-NEGF) method. We show that (surprisingly, despite their apparent simplicity, these Au/cysteine/Au nanowires are shown to be a convenient NDR device) the smallest two-terminal molecular wire can exhibit NDR behavior to date. Experiments with a conventional or novel self-assembled monolayer (SAM) are proposed to test these predictions. The projected density of states (PDOSs) and transmission coefficients T(E) under various...
Itinerant electron transport in microscopically inhomogeneous magnetic fields
, Article Journal of Magnetism and Magnetic Materials ; Volume 299, Issue 2 , 2006 , Pages 356-361 ; 03048853 (ISSN) ; Nogaret, A ; Atkinson, D ; Ghorbani, M ; Iraji Zad, A ; Sharif University of Technology
2006
Abstract
We report on magnetoresistance measurements in thin nickel films modulated by a periodic magnetic field emanating from micromagnetic arrays fabricated at the film surface. By increasing the strength of the magnetic potential using nickel and dysprosium micromagnets, we are able to quench the anisotropic magnetoresistance (AMR) in the film. © 2005 Elsevier B.V. All rights reserved
Enhanced performance of planar perovskite solar cells using TiO2/SnO2 and TiO2/WO3 bilayer structures: Roles of the interfacial layers
, Article Solar Energy ; Volume 208 , 2020 , Pages 697-707 ; Ranjbar, M ; Kermanpur, A ; Taghavinia, N ; Minbashi, M ; Forouzandeh, M ; Ebadi, F ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In planar perovskite solar cells (PSCs), engineering the extraction and recombination of electron–hole pairs by modification of the electron transport layer (ETL)/perovskite interface is very vital for obtaining high performance. The main idea here is to improve properties of the TiO2/perovskite interface by inserting an ultra-thin layer (UTL) of WO3 or SnO2 with the thickness of less than 10 nm by RF magnetron sputtering method. The structural and electrical characteristics of the samples were tested by XRD, AFM, FE-SEM, Mott-Schottky analysis, UV–Vis spectroscopy, J-V characterization and electrochemical impedance spectroscopy (EIS). It was found that the bilayer structured ETLs exhibit...
Stability Enhancing of Perovskite Solar Cell by Replacing TiO2 Mesoporous Layer with Oxide Perovskite Structures
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor) ; Seyed Reihani, Morteza (Supervisor)
Abstract
The purpose of this study is fabrication and characterization of a mesoporous Perovskite solar cell using Barium Titanate as the mesoporous electron transfer layer. In this study, TiO2 nanoparticles and BaTiO3 oxide perovskites were prepared by sol-gel synthesis method and their pastes were applied to the conductive substrate by spin coating method and applied to electron transfer layer in perovskite solar cells. Then Perovskite solar cells were fabricated with different structures from the electron transfer layer.The results of X-ray diffraction analysis showed that pure Barium Titanate and Titanium dioxide nanoparticles were successfully synthesized with tetragonal and cubic crystal...
Analytical and numerical study of quantum transport in an array of nanorings: A case study with double rings
, Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 47 , January , 2013 , Pages 297-302 ; 13869477 (ISSN) ; Khoeini, F ; Sharif University of Technology
2013
Abstract
We present an analytical method to obtain an expression for electron transmission through an array of disordered nanorings (ADNRs) sandwiched between two semi-infinite metallic leads in different lead-ring coupling strengths. Our approach is based on the nearest-neighbor tight-binding approximation and transfer matrix method. First, we derive an analytical formula for electron transmission across the system. Next, we apply our approach to study of the electron transport in a perfect double nanoring (PDNR) and design a NOR gate using the magnetic fluxes inputs. The conductance, current-voltage characteristics and threshold voltage of the system are calculated in the weak and strong coupling...