31. Self-Suspended Nanomesh Scaffold for Ultrafast Flexible Photodetectors Based on Organic Semiconducting CrystalsGvido Bratina, Egon Pavlica, 2018, original scientific article Abstract: Self-standing nanostructures are of fundamental interest in materials sci- ence and nanoscience and are widely used in (opto-)electronic and photonic devices as well as in micro-electromechanical systems. To date, large-area and self-standing nanoelectrode arrays assembled on flexible substrates
have not been reported. Here the fabrication of a hollow nanomesh scaffold on glass and plastic substrates with a large surface area over 1 mm2 and ultralow leakage current density (≈1–10 pA mm−2 @ 2 V) across the empty scaffold is demonstrated. Thanks to the continuous sub-micrometer space formed in between the nanomesh and the bottom electrode, highly crystalline and dendritic domains of 6,13-bis(triisopropylsilylethinyl)pentacene growing within the hollow cavity can be observed. The high degree of order at the supramolecular level leads to efficient charge and exciton transport; the pho- tovoltaic detector supported on flexible polyethylene terephthalate substrates exhibits an ultrafast photoresponse time as short as 8 ns and a signal-to- noise ratio approaching 105. Such a hollow scaffold holds great potential as a novel device architecture toward flexible (opto-)electronic applications based on self-assembled micro/nanocrystals. Keywords: nanostrukture, organski polprevodniki, fotonapetostne komponente Published in RUNG: 22.05.2018; Views: 3552; Downloads: 0 This document has many files! More... |
32. Negative field‐dependent charge mobility in crystalline organic semiconductors with delocalized transportFei Tong, Andrey Kadashchuk, Egon Pavlica, Gvido Bratina, 2018, original scientific article Abstract: Charge-carrier mobility has been investigated by time-of-flight (TOF) transient photocurrent in a lateral transport con- figuration in highly crystalline thin films of 2,7-dioctyl[1]benzothieno [3,2-b][1] benzothiophene (C8-BTBT) grown by a zone-casting alignment technique. High TOF mobility has been revealed that it is consistent with the delocalized nature of the charge transport in this material, yet it featured a positive temperature dependence at T ≥ 295 K. Moreover, the mobility was surprisingly found to decrease with electric field in the high-temperature region. These observations are not compat- ible with the conventional band-transport mechanism. We have elaborated an analytic model based on effective-medium approximation to rationalize the puzzling findings. The model considers the delocalized charge transport within the energy landscape formed by long-range transport band-edge variations in imperfect organic crystalline materials and accounts for the field-dependent effective dimensionality of charge transport percolative paths. The results of the model calculations are found to be in good agreement with experimental data. Keywords: time of flight, organic semiconductors, single crystals Published in RUNG: 07.05.2018; Views: 5222; Downloads: 0 This document has many files! More... |
33. Univerza v Novi Gorici, Spremljanje, ugotavljanje in zagotavljanje kakovosti, Poročilo za študijsko leto 2013/2014Iztok Arčon, Martina Bergant Marušič, Aleš Bogovič, Lorena Butinar, Gvido Bratina, IMRE CIKAJLO, Saša Dobričić, Elsa Fabbretti, Mladen Franko, Renata Kop, Urška Lavrenčič Štangar, Martin Knez, Katja Mihurko Poniž, Jana Laganis, Branka Mozetič Vodopivec, Egon Pavlica, Ingrid Petrič, Samo Stanič, Tea Stibilj Nemec, Arthur Stepanov, Boštjan Potokar, Veronika Piccinini, Peter Purg, Aljaž Rener, Nives Štefančič, Ana Toroš, Tanja Urbančič, Vanesa Valentinčič, Aleš Vaupotič, Sabina Zelinšček, 2014, treatise, preliminary study, study Keywords: zagotavljanje kakovosti, visoko šolstvo, univerza Published in RUNG: 05.02.2018; Views: 4157; Downloads: 0 This document has many files! More... |
34. Evidence of enhanced photocurrent response in corannulene filmsNadya Patukhova, Layla Martin Samos, Egon Pavlica, Gvido Bratina, 2017, original scientific article Abstract: Photoconductivity spectra measured in non-crystalline corannulene thin layers are compared to optical absorption in solution phase and thin films. The unexpected enhanced photoconductivity is correlated with GW–BSE theoretical predictions of corannulene gas-phase excitonic spectra. Theoretical analysis reveals a consistent contribution involving transitions to Super Atomic Molecular Orbitals (SAMOs), a unique set of diffuse orbitals typical of curved conjugated constructs. Results suggest SAMO population via direct photoexcitation as a potential mechanism towards exploiting these diffuse orbitals as conducting channels in suitably assembled quantum nanostructures or solids. Keywords: Coranulene, photoconductivity, thin layers, photoexcitation Published in RUNG: 26.09.2017; Views: 3800; Downloads: 204 Full text (644,91 KB) |
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37. Interface-controlled growth of organic semiconductors on grapheneJinta Mathews, Saim Emin, Egon Pavlica, Matjaž Valant, Gvido Bratina, 2017, original scientific article Abstract: We have studied submonolayer coverages of N,N-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDIF-CN2) on mechanically exfoliated graphene transferred onto SiO2 substrates. Our atomic force microscopy (AFM) data show that PDIF-CN2 forms irregularly-shaped 1.4 nm-high islands. From the selected area diffraction performed with transmission electron microscope (TEM) we conclude that this height corresponds to π−π
stacks of molecules, which are inclined for 43° relative to the graphene surface. AFM also showed complete absence of PDIF-CN2 on single-layer graphene (SLG). Electric force microscopy revealed a marked difference in surface charge density between a single-layer graphene and bilayer graphene, with a higher surface charge on SLG than on the bilayer graphene. We associate this behavior with p−
type doping of graphene due to the electrostatic dipole induced by the molecular water layer present at the graphene/SiO2 interface. The crucial role of the graphene/SiO2 interface in determining growth of PDIF-CN2 was further confirmed by TEM examination of PDIF-CN2 deposited onto unsupported SLG. Keywords: afm, organic semiconductors, graphene Published in RUNG: 18.05.2017; Views: 4756; Downloads: 0 This document has many files! More... |
38. Fast-Response Photonic Device Based on Organic-Crystal Heterojunctions Assembled into a Vertical-Yet-Open Asymmetric ArchitectureLei Zhang, Egon Pavlica, Zhong, Xiaolan, Liscio Fabiola, LI Songlin, Gvido Bratina, Orgiu Emanuele, Samori Paolo, 2017, original scientific article Keywords: organski polprevodniki, merjenja časa preleta, organski fotodetektorji Published in RUNG: 24.01.2017; Views: 4128; Downloads: 0 This document has many files! More... |
39. The role of local potential minima on charge transport in thin organic semiconductor layersEgon Pavlica, Raveendra Babu Penumala, Gvido Bratina, 2016, original scientific article Abstract: We have performed a systematic study of dependence of time-resolved photocurrent on the point of charge excitation within the organic semiconductor channel formed by two coplanar metal electrodes. The results confirm that spatial variation of electric field between the electrodes crucially determines transport of photogenerated charge carriers through the organic layer. Time-of-flight measurements of photocurrent demonstrate that the transit time of photogenerated charge carrier packets drifting between the two electrodes decreases with increasing travelling distance. Such counterintuitive result cannot be reconciled with the spatial distribution of electric field between coplanar electrodes, alone. It is also in contrast to expected role of space-charge screening of external electric field. Supported by Monte Carlo simulations of hopping transport in disordered organic semiconductor layer, we submit that the space-charge screens the external electric field and captures slower charge carriers from the photogenerated charge carrier packet. The remaining faster carriers, exhibit velocity distribution with significantly higher mean value and shorter transit time. Keywords: Charge transport, Organic semiconductors, Time of flight, Mobility, Traps Published in RUNG: 23.12.2016; Views: 5285; Downloads: 0 This document has many files! More... |
40. A nanomesh scaffold for supramolecular nanowire optoelectronic devicesLei Zhang, Egon Pavlica, Gvido Bratina, 2016, original scientific article Abstract: Supramolecular organic nanowires are ideal nanostructures for optoelectronics because they exhibit both efficient exciton generation as a result of their high absorption coefficient and remarkable light sensitivity due to the low number of grain boundaries and high surface-to-volume ratio. To harvest photocurrent directly from supramolecular nanowires it is necessary to wire them up with nanoelectrodes that possess different work functions. However, devising strategies that can connect multiple nanowires at the same time has been challenging. Here, we report a general approach to simultaneously integrate hundreds of supramolecular nanowires of N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) in a hexagonal nanomesh scaffold with asymmetric nanoelectrodes. Optimized PTCDI-C8 nanowire photovoltaic devices exhibit a signal-to-noise ratio approaching 107, a photoresponse time as fast as 10 ns and an external quantum efficiency >55%. This nanomesh scaffold can also be used to investigate the fundamental mechanism of photoelectrical conversion in other low-dimensional semiconducting nanostructures. Keywords: fotodetektor, organski polprevodnik, fotoprevodnost, organski kristal, elektronske komponente, nanožice Published in RUNG: 05.10.2016; Views: 5308; Downloads: 0 This document has many files! More... |