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1.
High charge carrier mobility in thin films of quasi-two-dimensional polyacetylenes with sulphuric inter-chain linkers
Nadiia Pastukhova, Gvido Bratina, Egon Pavlica, 2023, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Quasi-two-dimensional conjugated polymers (q2DCP) have been described and recognised as crystalline, one- or two-layer polymer nanosheets prepared by arranging linear conjugated polymer chains in a 2D plane via non-covalent interchain interactions.[1,2] The extension of polymer dimensionality to two dimensions improves the alignment of individual polymer layers and overcomes the limitations associated with charge carrier hopping between polymer chains in one-dimensional and crosslinked polymers [3] Compared to other two-dimensional materials such as graphene or transition metal dichalcogenides, q2DCPs offer a high degree of flexibility in chemical design and are compatible with liquid-based processing methods. Various q2DCPs have been synthesized by surface active monolayer-assisted interfacial synthesis (SMAIS) [5] The photoreaction of these materials is of particular interest due to their tunable properties such as band gap and associated wavelength-dependent photoexcitation, which enables a wide range of applications in optoelectronic devices. Using time-of-flight photoconductivity measurements (TOF-PC) [4], we investigate the charge transport properties of 2D polyacetylene prepared by the SMAIS method. A typical TOFP measurement of q2D polyacetylene is shown in Figure 1, using a focused nanosecond pulse laser at 325 nm and an electrode spacing of 250 µm. From the polarity of the bias voltage and the duration of the photocurrent, we can determine the polarity, velocity, and mobility of the photo-excited carriers as a function of the applied bias voltage and excitation wavelength. and observed electron mobility of 250 cm2/Vs, which is in the range of the most advanced organic single-crystal small-molecule semiconductors and almost an order of magnitude higher than linear polymeric semiconductors. We investigated the optical absorption and transmission on a lateral scale using scanning near-field optical microscopy (SNOM).
Ključne besede: 2D polymers, organic semiconductors, q2DPA, SNOM, time-of-flight photoconductivity
Objavljeno v RUNG: 25.03.2024; Ogledov: 76; Prenosov: 1
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2.
Začetne faze rasti organskih polprevodnikov na bazi tiofena na kvazi-dvodimenzionalnij polimerih poliacetilena
Volodymyr Rodin, 2023, objavljeni povzetek znanstvenega prispevka na konferenci

Ključne besede: organski polprevodniki, kvazi-dvodimenzionalni polimeri, poliacetilen
Objavljeno v RUNG: 25.03.2024; Ogledov: 87; Prenosov: 2
.pdf Celotno besedilo (550,24 KB)

3.
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Organic and flexible : lecture at Ženske v znanosti in za znanost, Ljubljana, 12. 2. 2024
Nadiia Pastukhova, 2024, prispevek na konferenci brez natisa

Opis: The development of organic semiconductors (OS) opens a new perspective and possibilities for novel device architectures including flexible and wearable electronics. One of the key parameters is the charge carriers' mobility. In OSs, it is affected by many factors, including molecular stacking, chemical impurities, temperature, pressure, electric field, and charge carrier density. These factors can affect the structural or energetic disorder. To overcome limitations, new polymers that extend the π-conjugation to two dimensions were developed. The two-dimensional network structure provides a high degree of structural stability and tunability of properties, while the organic molecules can be engineered to exhibit specific chemical and physical properties such as large surface area, pore size, and electronic properties. I will present our recent research, where quasi-2D polyacetylene (q2DPA) demonstrates high electron mobility along the direction of the layer, measured by the lateral time-of-flight photoconductivity (TOF) method.
Ključne besede: 2D polymers, time-of-flight photoconductivity, TOF, organic semiconductors
Objavljeno v RUNG: 22.03.2024; Ogledov: 136; Prenosov: 2
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5.
Designing atomic interface in ▫$Sb_2S_3/CdS$▫ heterojunction for efficient solar water splitting
Minji Yang, Zeyu Fan, Jinyan Du, Chao Feng, Ronghua Li, Beibei Zhang, Nadiia Pastukhova, Matjaž Valant, Matjaž Finšgar, Andraž Mavrič, Yanbo Li, 2024, izvirni znanstveni članek

Opis: In the emerging Sb2S3‐based solar energy conversion devices, a CdS buffer layer prepared by chemical bath deposition is commonly used to improve the separation of photogenerated electron‐hole pairs. However, the cation diffusion at the Sb2S3/CdS interface induces detrimental defects but is often overlooked. Designing a stable interface in the Sb2S3/CdS heterojunction is essential to achieve high solar energy conversion efficiency. As a proof of concept, this study reports that the modification of the Sb2S3/CdS heterojunction with an ultrathin Al2O3 interlayer effectively suppresses the interfacial defects by preventing the diffusion of Cd2+ cations into the Sb2S3 layer. As a result, a water‐splitting photocathode based on Ag:Sb2S3/Al2O3/CdS heterojunction achieves a significantly improved half‐cell solar‐to‐hydrogen efficiency of 2.78% in a neutral electrolyte, as compared to 1.66% for the control Ag:Sb2S3/CdS device. This work demonstrates the importance of designing atomic interfaces and may provide a guideline for the fabrication of high‐performance stibnite‐type semiconductor‐based solar energy conversion devices.
Ključne besede: alumina, defect passivation, interface engineering, photoelectrochemical water splitting
Objavljeno v RUNG: 11.03.2024; Ogledov: 154; Prenosov: 2
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6.
Stable seawater oxidation with a self-healing oxygen-evolving catalyst
Xiaojian Zhang, Chao Feng, Zeyu Fan, Beibei Zhang, Yequan Xiao, Andraž Mavrič, Nadiia Pastukhova, Matjaž Valant, Yi-Fan Han, Yanbo Li, 2023, izvirni znanstveni članek

Opis: Direct seawater electrolysis is key to massive hydrogen fuel production without the depletion of precious freshwater resources and the need for high-purity electrolytes. However, the presence of high-concentration chloride ions (Cl−) and alkaline-earth metal ions (Mg2+, Ca2+) poses great challenges to the stability and selectivity of the catalysts for seawater splitting. Here, we demonstrate a self-healing oxygen evolution reaction (OER) catalyst for long-term seawater electrolysis. By suppressing the competitive chlorine evolution reaction and precipitating the alkaline-earth metal ions through an alkaline treatment of the seawater, stable seawater oxidation is achieved owing to the self-healing ability of the borate-intercalated nickel–cobalt–iron oxyhydroxides (NiCoFe-Bi) OER catalyst under highly-alkaline conditions. The self-healing NiCoFe-Bi catalyst achieves stable seawater oxidation at a large current density of 500 mA cm−2 for 1000 h with near unity Faraday efficiency. Our results have demonstrated strong durability and high OER selectivity of the self-healing catalyst under harsh conditions, paving the way for industrial large-scale seawater electrolysis.
Ključne besede: chemistry, electrocatalysis, seawater oxidation, oxygen evolution reaction
Objavljeno v RUNG: 08.05.2023; Ogledov: 998; Prenosov: 2
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7.
Time-of-flight photoconductivity investigation of high charge carrier mobility in ▫$Ti_3C_2T_x$▫ MXenes thin-film
Jurij Urbančič, Erika Tomsic, Manisha Chhikara, Nadiia Pastukhova, Vadym Tkachuk, Alex Dixon, Andraž Mavrič, Payam Hashemi, Davood Sabaghi, Ali Shaygan Nia, Gvido Bratina, Egon Pavlica, 2023, izvirni znanstveni članek

Opis: Charge transport through a randomly oriented multilayered network of two-dimensional (2D) Ti3C2Tx (where Tx is the surface termination and corresponds to O, OH and F) was studied using time-of-flight photoconductivity (TOFP) method, which is highly sensitive to the distribution of charge carrier velocities. We prepared samples comprising Ti3C2Tx with thickness of 12 nm or 6-monolayers. MXene flakes of size up to 16 μm were randomly deposited on the surface by spin-coating from water solution. Using TOFP, we have measured electron mobility that reached values up to 279 cm2/Vs and increase with electric-field in a Poole-Frenkel manner. These values are approximately 50 times higher than previously reported field-effect mobility. Interestingly, our zero-electric-field extrapolate approaches electron mobility measured using terahertz absorption method, which represents intra-flake transport. Our data suggest that macroscopic charge transport is governed by two distinct mechanisms. The high mobility values are characteristic for the intra-flake charge transport via the manifold of delocalized states. On the other hand, the observed Poole-Frenkel dependence of charge carrier mobility on the electric field is typical for the disordered materials and suggest the existence of an important contribution of inter-flake hopping to the overall charge transport.
Ključne besede: charge transport, multilayered network, flakes, time-of-flight photoconductivity, MXene exfoliation, high-mobility solution-cast thin-film, semiconducting MXene
Objavljeno v RUNG: 31.03.2023; Ogledov: 1069; Prenosov: 2
.pdf Celotno besedilo (1,97 MB)

8.
Photoexcited charge mobility in quasi two-dimensional polyacetylene
Nadiia Pastukhova, Kejun Liu, Renhao Dong, Gvido Bratina, Xinliang Feng, Egon Pavlica, 2022, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Two-dimensional conjugated polymers (2DCPs) have been described and recognised as crystalline, one- to two-layer polymer nanosheets prepared by 2D covalent polymerization exhibiting strong in-plane π-electron delocalization with two orthogonal directions and weak out-of-plane π-π stacking.[1,2] The extension of polymer dimensionality into two dimensions improves the alignment of individual polymer sheets and overcomes the limitations associated with charge carrier hopping between polymer chains in one-dimensional and crosslinked polymers.[3] Compared to other two-dimensional materials such as graphene or transition metal dichalcogenides, 2DCPs offer a high degree of flexibility in chemical design and are compatible with liquid-based processing methods. Various 2DCPs have been synthesised by surfactant monolayer-assisted interfacial synthesis (SMAIS).[5] Of particular interest is the photoresponse of these materials due to their tunable properties, such as bandgap and associated wavelength-dependent photoexcitation, which enables a wide range of applications in optoelectronic devices. Using time-of-flight photoconductivity (TOF-PC) measurements [4], we investigate the charge transport properties of 2D polyacetylene prepared by SMAIS method. We preform TOF-PC measurement of 2D polyacetylene using a focused nanosecond pulse laser at 325 nm and electrode separation of 250 µm. From the bias polarity and time duration of the photocurrent, we can determine the polarity, velocity and mobility of photoexcited charge carriers as a function of applied bias voltage and excitation wavelength. Using excitation at 325 m, we observed an electron mobility in the range of 150 cm2 V-1 s-1, which is in the realm of most advances small-molecule single-crystal organic semiconductors and almost an order of magnitude higher than linear polymeric semiconductors.
Ključne besede: Two-dimensional conjugated polymers, 2DCPs, 2Dpolymers, charge mobility, time-of-flight photoconductivity
Objavljeno v RUNG: 29.11.2022; Ogledov: 930; Prenosov: 0
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9.
Plasma-enhanced atomic layer deposition of amorphous Ga2O3 for solar-blind photodetection
Ze-Yu Fan, Min-Ji Yang, Bo-Yu Fan, Andraž Mavrič, Nadiia Pastukhova, Matjaž Valant, Bo-Lin Li, Kuang Feng, Dong-Liang Liu, Guang-Wei Deng, Qiang Zhou, Yan-Bo Li, 2022, izvirni znanstveni članek

Opis: Wide-bandgap gallium oxide (Ga2O3) is one of the most promising semiconductor materials for solar-blind (200 nm–280 nm) photodetection. In its amorphous form, a-Ga2O3 maintains its intrinsic optoelectronic properties while can be prepared at a low growth temperature, thus is compatible with Si integrated circuits (ICs) technology. Herein, the a-Ga2O3 film is directly deposited on pre-fabricated Au interdigital electrodes by plasma enhanced atomic layer deposition (PE-ALD) at a growth temperature of 250 °C. The stoichiometric a-Ga2O3 thin film with a low defect density is achieved owing to the mild PE-ALD condition. As a result, the fabricated Au/a-Ga2O3/Au photodetector shows a fast time response, high responsivity, and excellent wavelength selectivity for solar-blind photodetection. Furthermore, an ultra-thin MgO layer is deposited by PE-ALD to passivate the Au/a-Ga2O3/Au interface, resulting in the responsivity of 788 A/W (under 254 nm at 10 V), a 250-nm-to-400-nm rejection ratio of 9.2×103, and the rise time and the decay time of 32 ms and 6 ms, respectively. These results demonstrate that the a-Ga2O3 film grown by PE-ALD is a promising candidate for high-performance solar-blind photodetection and potentially can be integrated with Si ICs for commercial production.
Ključne besede: Amorphous gallium oxide, Passivation layer, Plasma enhanced atomic layer deposition, Responsivity, Solar-blind photodetector
Objavljeno v RUNG: 25.10.2022; Ogledov: 1055; Prenosov: 0
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10.
Enhancement of indacenodithiophene–benzothiadiazole copolymer field-effect mobility with MXenes
Jurij 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: 1082; Prenosov: 9
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