11. Enhancement of indacenodithiophene–benzothiadiazole copolymer field-effect mobility with MXenesJurij Urbančič, Nadiia Pastukhova, Manisha Chhikara, Hu Chen, Iain Mcculloch, Huanhuan Shi, Ali Shaygan Nia, Xinliang Feng, Egon Pavlica, Gvido Bratina, 2022, objavljeni povzetek znanstvenega prispevka na konferenci Opis: The predominant mode of charge carrier transport in thin layers of organic semiconductors (OSs) is thermally-activated hopping between localized states. This results in lower charge mobility compared to inorganic semiconductors precluding the use of OSs in high-speed electronic devices. Therefore, significant effort is invested to improve charge carrier mobility of OS thin layers, which form the basis of most of the organic electronic devices. Recent advances in the field of two-dimensional (2D) materials stimulated their use as addition to OS thin layers to boost the charge carrier mobility. MXenes promise to deliver most of the benefits of 2D materials coupled with large scale fabrication capability. Herein we examined Ti3C2X (X is O or OH group termination) MXene, as a candidate to improve charge carrier mobility in thin layer of indacenodithiophene-co-benzothiadiazole (IDTBT), a polymer exhibiting high electron mobility in defect-free crystalline layers. In our work we demonstrate that improvement in electron mobility in solution-cast IDTBT thin layers can be achieved by depositing a non-connected network of MXene flakes at the gate-dielectric/IDBT interface. Bottom-gate field-effect transistors (FETs) comprising of Au electrodes on n-doped silicon wafer covered with 230 nm of thermally deposited SiO2 were prepared and characterized. Charge carrier mobilities determined from transfer characteristics of FETs composing neat IDTBT channels were found to be in the range of 1 - 2×10−2 cm2/Vs. Devices comprising MXene flakes at the interface between SiO2 and IDTBT, instead exhibited a factor of four increase in electron mobility, while preserving the on/off ratio of 104. Ključne besede: MXene, IDTBT, charge carrier mobility, OFET Objavljeno v RUNG: 20.10.2022; Ogledov: 1159; Prenosov: 9 Povezava na celotno besedilo Gradivo ima več datotek! Več... |
12. Coevaporation of doped inorganic carrier-selective layers for high-performance inverted planar perovskite solar cellsJiexuan Jiang, Andraž Mavrič, Nadiia Pastukhova, Matjaž Valant, Qiugui Zeng, Zeyu Fan, Beibei Zhang, Yanbo Li, 2022, izvirni znanstveni članek Opis: Inorganic carrier selective layers (CSLs), whose conductivity can be effectively tuned by doping, offer low-cost and stable alternatives for their organic counterparts in perovskite solar cells (PSCs). Herein, we employ a dual-source electron-beam co-evaporation method for the controlled deposition of copper-doped nickel oxide (Cu:NiO) and tungsten-doped niobium oxide (W:Nb2O5) as hole and electron transport layers, respectively. The mechanisms for the improved conductivity using dopants are investigated. Owing to the improved conductivity and optimized band alignment of the doped CSLs, the all-inorganic-CSLs-based PSCs achieves a maximum power conversion efficiency (PCE) of 20.47%. Furthermore, a thin titanium buffer layer is inserted between the W:Nb2O5 and the silver electrode to prevent the halide ingression and improve band alignment. This leads to a further improvement of PCE to 21.32% and a long-term stability (1200 h) after encapsulation. Finally, the large-scale applicability of the doped CSLs by co-evaporation is demonstrated for the device with 1 cm2 area showing a PCE of over 19%. Our results demonstrate the potential application of the co-evaporated CSLs with controlled doping in PSCs for commercialization. Ključne besede: carrier selective layers, Cu-doped nickel oxide, electron-beam evaporation, perovskite solar cells, W-doped niobium oxide Objavljeno v RUNG: 17.03.2022; Ogledov: 1791; Prenosov: 121 Celotno besedilo (1,38 MB) Gradivo ima več datotek! Več... |
13. Interface engineering of Ta[sub]3N[sub]5 thin film photoanode for highly efficient photoelectrochemical water splittingJie Fu, Zeyu Fan, Mamiko Nakabayashi, Huanxin Ju, Nadiia Pastukhova, Yequan Xiao, Chao Feng, Naoya Shibata, Kazunari Domen, Yanbo Li, 2022, izvirni znanstveni članek Opis: Interface engineering is a proven strategy to improve the efficiency of thin film semiconductor based solar energy conversion devices. Ta3N5 thin film photoanode is a promising candidate for photoelectrochemical (PEC) water splitting. Yet, a concerted effort to engineer both the bottom and top interfaces of Ta3N5 thin film photoanode is still lacking. Here, we employ n-type In:GaN and p-type Mg:GaN to modify the bottom and top interfaces of Ta3N5 thin film photoanode, respectively. The obtained In:GaN/Ta3N5/Mg:GaN heterojunction photoanode shows enhanced bulk carrier separation capability and better injection efficiency at photo- anode/electrolyte interface, which lead to a record-high applied bias photon-to-current efficiency of 3.46% for Ta3N5-based photoanode. Furthermore, the roles of the In:GaN and Mg:GaN layers are distinguished through mechanistic studies. While the In:GaN layer con- tributes mainly to the enhanced bulk charge separation efficiency, the Mg:GaN layer improves the surface charge inject efficiency. This work demonstrates the crucial role of proper interface engineering for thin film-based photoanode in achieving efficient PEC water splitting. Ključne besede: photocatalysis, renewable energy Objavljeno v RUNG: 09.02.2022; Ogledov: 1744; Prenosov: 74 Povezava na celotno besedilo Gradivo ima več datotek! Več... |
14. Atomic layer deposition for the photoelectrochemical applicationsNadiia Pastukhova, Andraž Mavrič, Yanbo Li, 2021, pregledni znanstveni članek Opis: Substantial progress has been made in the photoelectrochemical (PEC) field to understand the photoelectrode behavior, semiconductor‐electrolyte interface, and photocorrosion, enabling new photoelectrode architectures with higher photocurrent, reduced photovoltage losses, and longer lifetime. Nevertheless, for practical PEC applications additional efforts are still needed to optimize all components of the photoelectrodes, including the light absorbing semiconductors, the layers for charge extraction, charge transfer, corrosion protection, and catalysis. In this regard, atomic layer deposition (ALD) offers new opportunities due to the monolayer‐by‐monolayer deposition approach, allowing preparation of conformal films with precisely controlled thickness and composition. As the ALD instruments are becoming widely accessible, this review aims to make an overview of the applications for photoelectrodes fabrication. The deposition of semiconductors onto flat and nano‐textured substrates, the deposition of ultrathin interlayers to ease charge transport by energy band alignment and surface states passivation, the deposition of corrosion protection layers, and finally, the possibilities for high catalyst dispersion is presented. Ključne besede: atomic layer deposition, charge recombination, charge transfer, photocorrosion, photoelectrochemical water splitting Objavljeno v RUNG: 25.02.2021; Ogledov: 2232; Prenosov: 139 Povezava na celotno besedilo Gradivo ima več datotek! Več... |
15. A pyrrolopyridazinedione-based copolymer for fullerene-free organic solar cellsAstrid-Caroline Knall, Samuel Rabensteiner, Sebastian F. Hoefler, Matiss Reinfelds, Mathias Hobisch, Heike M. A. Ehmann, Nadiia Pastukhova, Egon Pavlica, Gvido Bratina, Illie Hanzu, Shuguang Wen, Renqiang Yang, Gregor Trimmel, Thomas Rath, 2021, izvirni znanstveni članek Opis: The recent success of non-fullerene acceptors in organic photovoltaics also entails a change in the requirements to the polymer donor in terms of optical and morphological properties leading to a demand for novel conjugated polymers. Herein, we report on the synthesis of a 1,4-bis-(thiophene-2-yl)-pyrrolopyridazinedione based copolymer with 2-ethylhexyl substituents on the pyrrolopyridazinedione moiety. A 2D conjugated benzodithiophene (BDT) was chosen as comonomer. The resulting copolymer T-EHPPD-T-EHBDT showed a molecular weight of 10.2 kDa, an optical band gap of 1.79 eV, a hole mobility of 1.8 × 10−4 cm2 V−1 s−1 and a preferred face-on orientation with regard to the substrate. The comparably wide band gap as well as the determined energy levels (HOMO: −5.47 eV, LUMO: −3.68 eV) match well with the narrow band gap non-fullerene acceptor ITIC-F, which was used as the acceptor phase in the bulk heterojunction absorber layers in the investigated solar cells. The solar cells, prepared in inverted architecture, revealed power conversion efficiencies up to 7.4% using a donor:acceptor ratio of 1 : 1 in the absorber layer. Ključne besede: non-fullerene solar cells, charge transport, charge mobility, power conversion efficiency Objavljeno v RUNG: 27.01.2021; Ogledov: 2576; Prenosov: 0 Gradivo ima več datotek! Več... |
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17. Ultraviolet absorption and transient photocurrent spectroscopy in organic thin layers as evidence of super atomic molecular orbitals in corannuleneNadiia Pastukhova, Layla Martin-Samos, Laura Zoppi, Egon Pavlica, Jinta Mathew, Gvido Bratina, J. S. Siegel, Kim K. Baldridge, 2018, objavljeni povzetek znanstvenega prispevka na konferenci Ključne besede: photocurrent spectroscopy, organic thin layers, atomic molecular orbitals Objavljeno v RUNG: 03.11.2020; Ogledov: 2579; Prenosov: 71 Povezava na celotno besedilo Gradivo ima več datotek! Več... |
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20. PHOTO-EXCITATION ENERGY INFLUENCE ON THE PHOTOCONDUCTIVITY OF ORGANIC SEMICONDUCTORSNadiia Pastukhova, 2018, doktorska disertacija Opis: In this work, we experimentally studied the influence of photoexcitation energy
influence on the charge transport in organic semiconductors. Organic semiconductors
were small molecules like corannulene, perylene and pentacene derivatives, polymers
such as polythiophene and benzothiophene derivatives, and graphene, along with
combinations of these materials in heterojunctions or composites.
The first part of this study is focused on the photoexcitation energy influence on
the transient photoconductivity of non-crystalline curved π-conjugated corannulene
layers. The enhanced photoconductivity, in the energy range where optical absorption
is absent, is deduced from theoretical predictions of corannulene gas-phase excited
state spectra. Theoretical analysis reveals a consistent contribution involving
transitions to Super Atomic Molecular Orbitals (SAMOs), a unique set of diffuse
orbitals typical of curved π-conjugated molecules. More, the photoconductivity of the
curved corannulene was compared to the π-conjugated planar N,N′-1H,1H-
perfluorobutyldicyanoperylene-carboxydi-imide
(PDIF-CN2),
where
the
photoexcitation energy dependence of photocurrent closely follows the optical
absorption spectrum.
We next characterized charge transport in poly(3-hexylthiophene) (P3HT) layers
deposited from solution. Our results indicate that time-of-flight (TOF) mobility
depends on the photoexcitation energy. It is 0.4× 10 −3 cm 2 /Vs at 2.3 eV (530 nm) and
doubles at 4.8 eV (260 nm). TOF mobility was compared to field-effect (FET) mobility
of P3HT field-effect transistors (OFETs). The FET mobility was similar to the 2.3 eV
excitation TOF mobility. In order to improve charge mobility, graphene nanoparticles
were blended within a P3HT solution before the deposition. We found that the mobility
significantly improves upon the addition of graphene nanoparticles of a weight ratio
as low as 0.2 %. FET mobility increases with graphene concentration up to a value of
2.3× 10 −2 cm 2 /Vs at 3.2 %. The results demonstrate that phase segregation starts to
influence charge transport at graphene concentration of 0.8 % and above. Hence, the
graphene cannot form a bridged conduction channel between electrodes, which would
cancel the semiconducting effect of the polymer composite.
An alternative approach to enhance mobility is to optimize the molecular ordering
of organic semiconductors. For that purpose, we studied an innovative nanomesh
device. Free-standing nanomesh devices were used to form nanojunctions of N,N′-
iiDioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) nanowires and crystalline
bis(triisopropylsilylethinyl)pentacene (TIPS-PEN). We characterized the photocurrent
response time of this novel nanomesh scaffold device. The photoresponse time
depends on the photon energy. It is between 4.5 − 5.6 ns at 500 nm excitation
wavelength and between 6.7 − 7.7 ns at 700 nm excitation wavelength. In addition, we
found that thermal annealing reduces charge carrier trapping in crystalline nanowires.
This confirms that the structural defects are crucial to obtaining high photon-to-charge
conversion efficiency and subsequent transport from pn junction in heterostructured
materials.
Structural defects also influence the power conversion efficiency of organic
heterostructured photovoltaics (OPVs). Anticipating that polymers with different
backbone lengths produce different level of structural defects, we examined charge
transport
dependence
on
the
molecular
weight
of
poly[4,8-bis(5-(2-
ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-
ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl]
(PTB7-Th)
from 50 kDa to 300 kDa. We found p-type hopping transport in PTB7-Th,
characterized by 0.1 – 3× 10 −2 cm 2 /Vs mobility, which increases with temperature and
electric field. The polymer molecular weight exhibits a non-trivial influence on charge
transport. FET mobility in the saturation regime increases with molecular weight. A
similar trend is observed in TOF mobility and FET mobility in the linear regime,
except for the 100kDa polymer, which manifests in the highest mobility due to reduced
charge trapping. The lowest trapping at the dielectric interface of OFET is observed at
200 kDa. In addition, the 200 kDa polymer exhibits the lowest activation energy of the
charge transport. Although the 100 kDa polymer indicates the highest mobility, OPVs
using the 200 kDa polymer exhibit the best performance in terms of power conversion
efficiency. Ključne besede: organic
semiconductors, optical
absorption
spectroscopy, time-of-flight
photoconductivity, transient photocurrent spectroscopy, organic thin film transistors, atomic force microscopy, superatomic molecular orbitals, pn heterojunction, organic
nanowires, graphene, composites, charge mobility, charge trapping, temperature
dependence, photodetector, photovoltaic, solar cell, organic electronics Objavljeno v RUNG: 08.10.2018; Ogledov: 5485; Prenosov: 164 Celotno besedilo (4,56 MB) |