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1.
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: 524; Downloads: 0
.pdf Fulltext (1,78 MB)

2.
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
Summary of found: ...organski polprevodniki, grafen, transport električnega naboja...
Keywords: organski polprevodniki, grafen, transport električnega naboja
Published: 13.10.2020; Views: 112; Downloads: 0
.pdf Fulltext (2,64 MB)

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