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Electronic transport properties of graphene and graphene-related materials
Srinivasa Rao Pathipati, 2014, doctoral dissertation

Found in: ključnih besedah
Summary of found: ...grafen, reduciran grafenov oksid, transport naboja, čas preleta, organski tranzistor, adsorbati, dopiranje, zmesi,...
Keywords: grafen, reduciran grafenov oksid, transport naboja, čas preleta, organski tranzistor, adsorbati, dopiranje, zmesi, perileni, politiofeni, grafenski nanotrakovi, disertacije
Published: 22.01.2015; Views: 2483; Downloads: 100
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Transport električnega naboja v organskih polprevodnikih, simulacija po metodi Monte Carlo
Robert Hudej, Gvido Bratina, Egon Pavlica, 2003, original scientific article

Abstract: The electric-charge transport in organic semiconductors is essentially different to the transport in ordered inorganic crystals. The reason is in thelocalization of the energy states, which act as charge-carrier transport channels between molecules. Consequently, the determination of the basic transport parameters in organic materials is inherently more involved than in their inorganic counterparts. The analytical methods that are used to describe charge transport in inorganic materials are unsuitable, since they are based on the extended electronic energy structure. We report here on the simulation of charge transport in organic semiconductor thin films. The simulation is based on the Monte Carlo method and describes the charge-carrier transport within the framework of carrier hopping between the sites. We employed a Gaussian energy distribution of the hopping sites with disorder elements. The degree of disorder is characterized by the width of the Gaussian distribution and is measured in eV units. The results of the transport simulation in 3,4,9,10-perylenedianhydride tetracarboxylic acid (PTCDA) show that the photogenerated charge-carrier current depends on the film thickness, temperature and disorder degree. The simulated photocurrents have the same amplitude in thick films as in the thin films, but the overall shape of the I(t) curve is more dispersive in thin films. The charge-carrier mobility decreases with the increasing degree of disorder at a given temperature. The simulation of the photogenerated positive charge carriers current matches with the time-of-flight experiment in a glass/ITO/PTCDA(600 nm)/In heterostructure at room temperature and an applied bias voltage of 8 V.
Found in: ključnih besedah
Keywords: neurejeni kristali, metoda Monte Carlo, organski polprevodniki, transport naboja, PTCDA, tranzientne meritve
Published: 10.07.2015; Views: 2779; Downloads: 9
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Enhancement of Charge Transport in Polythiophene Semiconducting Polymer by Blending with Graphene Nanoparticles
Egon Pavlica, Gvido Bratina, 2019, original scientific article

Abstract: This paper describes a study on the charge transport in a composite of liquid‐exfoliated graphene nanoparticles (GNPs) and a polythiophene semiconducting polymer. While the former component is highly conducting, although it consists of isolated nanostructures, the latter offers an efficient charge transport path between the individual GNPs within the film, overall yielding enhanced charge transport properties of the resulting bi‐component system. The electrical characteristics of the composite layers were investigated by means of measurements of time‐of‐flight photoconductivity and transconductance in field‐effect transistors. In order to analyze both phenomena separately, charge density and charge mobility contributions to the conductivity were singled out. With the increasing GNP concentration, the charge mobility was found to increase, thereby reducing the time spent by the carriers on the polymer chains. In addition, for GNP loading above 0.2 % (wt.), an increase of free charge density was observed that highlights an additional key role played by doping. Variable‐range hopping model of a mixed two‐ and three‐dimensional transport is explained using temperature dependence of mobility and free charge density. The temperature variation of free charge density was related to the electron transfer from polythiophene to GNP, with an energy barrier of 24 meV.
Found in: ključnih besedah
Summary of found: ...grafen, polimeri, transport električnega naboja, časovno odvisna fotoprevodnost...
Keywords: grafen, polimeri, transport električnega naboja, časovno odvisna fotoprevodnost
Published: 23.08.2019; Views: 446; Downloads: 0
.pdf Fulltext (1,78 MB)

Molecular alignment on graphene surface determines transport properties of graphene/organic semiconductor transistors
Gvido Bratina, Egon Pavlica, Vadym Tkachuk, 2020, original scientific article

Abstract: Graphene field-effect transistor structures were used to investigate the role of molecular alignment on charge transport properties of heterostructures comprising a single-layer graphene and variable thickness of N,N′-bis(n-octyl)-(1,7&1,6)-dicyanoperylene-3,4:9,10-bisdicarboximide (PDI8-CN2) - an n-type organic semiconductor. Our atomic force microscopy data show that under selected growth conditions PDI8-CN2 grows in a layer-by-layer fashion up to a second monolayer. The first layer comprises flat-lying molecules, whereas the molecules in the second layer orient themselves in an upright orientation. Transconductance measurements show that the flat-lying molecules have little effect on the position of the Fermi level in graphene. Upright oriented molecules in the second layer instead, have a strong effect as to neutralize native p-type doping of graphene and cause a shift of charge-neutrality level towards the Dirac point. We interpret such behavior in terms of different orientation of the surface dipole on layers with different molecular orientations. At the same time the overall mobility of the charge carriers reaches values exceeding 3000 cm2/Vs.
Found in: ključnih besedah
Keywords: organski polprevodniki, grafen, transport električnega naboja
Published: 13.10.2020; Views: 41; Downloads: 0
.pdf Fulltext (2,64 MB)

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