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Search results for: THEORETICAL DESIGNING OF SELENIUM HETEROCYCLIC NON‑FULLERENE ACCEPTORS WITH ENHANCED POWER CONVERSION EFCIENCY FOR ORGANIC SOLAR CELLS: A DFT/TD‑DFT‑BASED PREDICTION AND UNDERSTANDING
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Theoretical designing of selenium heterocyclic non-fullerene acceptors with enhanced power conversion efficiency for organic solar cells: a DFT/TD-DFT-based prediction and understanding
PublicationIn this study, we have designed and explored a new series of non-fullerene acceptors for possible applications in organic solar cells. We have designed four molecules named as APH1 to APH4 after end-capped modification of recently synthesized Y6-Se-4Cl molecule. Density functional theory and time dependent-density functional theory have been employed for computing geometric and photovoltaic parameters of the designed molecules....
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Designing efficient A-D-A1-D-A type fullerene free acceptor molecules with enhanced power conversion efficiency for solar cell applications
PublicationThe achievement of highly efficient power conversion efficiency (PCE) is a big concern for non-fullerene organic solar cells (NF-OSCs) because PCE can depend on numerous variables. Here, new five novel acceptor molecules without fullerenes were developed and investigated using DFT (density functional theory) and TD-DFT (time dependent-density functional theory). Compared to the recently synthesized molecule (PZ-dIDTC6), the developed...
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DFT and NBO theoretical study of protonation of tri-tert-butoxysilanethiol and its anion
PublicationWykonano obliczenia kwantowo-chemiczne metodą DFT dla tri-tert-butoksysilanotiolu oraz jego protonowanych i deprotonowanych form, zarówno na atomie tlenu jak i siarki. Przeanalizowano bilans energetyczny dla protonowania anionu w próżni i w fazie wodnej (stosując model IPCM). Zaobserwowano skrócenie wiązania Si-S w wyniku protonowania na atomie tlenu. Zmiany długości wiązań Si-O i Si-S zostały zinterpretowane w oparciu o analizę...
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Conformational analysis of N-isopropylbenzohydroxamic acids:Crystal structure, DFT and NMR studies
PublicationCelem pracy było znalezienie różnic strukturalnych dwóch wybranych kwasów N-izopropylobenzhydroksamowych, które rzutują na ich zaobserwowaną wcześniej zróżnicowaną reaktywność wobec odczynników elektrofilowych i porównanie ich budowy z budową znanych kwasów N-metylobenzhydroksamowych. Na podstawie analizy rentgenostrukturalnej monokryształu, obliczeń kwantowo-mechanicznych metodami ab initio oraz DFT w fazie gazowej oraz wyników...
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Core–shell excitation of isoxazole at the C, N, and O K-edges – an experimental NEXAFS and theoretical TD-DFT study
PublicationThe near-edge X-ray absorption fine structure (NEXAFS) spectra of the gas-phase isoxazole molecule have been measured by collecting total ion yields at the C, N, and O K-edges. The spectral structures have been interpreted using time-dependent density functional theory (TD-DFT) with the short-range corrected SRC2-BLYP exchange–correlation functional. Experimental and calculated energies of core excitations are generally in good...
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Singlet oxygen in the removal of organic pollutants: An updated review on the degradation pathways based on mass spectrometry and DFT calculations
PublicationThe degradation of pollutants by a non-radical pathway involving singlet oxygen (1O2) is highly relevant in advanced oxidation processes. Photosensitizers, modified photocatalysts, and activated persulfates can generate highly selective 1O2 in the medium. The selective reaction of 1O2 with organic pollutants results in the evolution of different intermediate products. While these products can be identified using mass spectrometry...
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Electrical properties of organic and perovskite systems used in solar cells
PublicationNowadays, a great progress in the areas of molecular and hybrid photovoltaics is observed. The devices based on organic and perovskite materials are getting attention mostly due to their low cost production process. However, their efficiency and stability are still lower than for inorganic materials which make them less popular. Therefore, a detailed understanding of the device physics is fundamental for organic and perovskite...
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Influence of excitons interaction with charge carriers on photovoltaic parameters in organic solar cells
PublicationWe report on theoretical analysis of excitons annihilation on charge carriers in organic solar cells. Numerical calculations based on transient one-dimensional drift-diffusion model have been carried out. An impact of three quantities (an annihilation rate constant, an exciton mobility and a recombination reduction factor) on current density and concentrations of charge carriers and excitons is investigated. Finally, we discuss...
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Atmospheric degradation mechanism of anthracene initiated by OH•: A DFT prediction
PublicationDensity functional theory (DFT) calculations at the M06-2X/def2-TZVP level have been employed to investigate the atmospheric oxidation mechanism of anthracene (ANT) initiated by HO•. Direct hydrogen atom abstraction from the ANT using HO• takes place hardly at ambient conditions while the addition of HO• to the C1, C2, and C4 sites are thermodynamically and kinetically more advantageous. The addition reactions are controlled by...
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DFT-based prediction of reactivity of short-chain alcohol dehydrogenase
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Photocatalysts for Solar Energy Conversion
PublicationPhotocatalytic oxidation over suspended solid photocatalysts (e.g., titanium dioxide) has been proposed as a sustainable process for treatment and purification of water and wastewater as well as the process for photoconversion of solar energy to hydrogen, methane, and other low hydrocarbons. Solar radiation could be used to drive heterogeneous electrochemical reactions at the surface of an optically active photocatalyst (e.g.,...
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Ligand-Modified Boron-Doped Diamond Surface: DFT Insights into the Electronic Properties of Biofunctionalization
PublicationWith the increasing power of computation systems, theoretical calculations provide a means for quick determination of material properties, laying out a research plan, and lowering material development costs. One of the most common is Density Functional Theory (DFT), which allows us to simulate the structure of chemical molecules or crystals and their interaction. In developing a new generation of biosensors, understanding the nature...
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Magnetic field effects in dye-sensitized and organic solar cells
PublicationThe charge recombination and exciton dissociation are generally recognized as the basic electronic processes limiting the efficiency of photovoltaic devices. The aim of this thesis is to understand the electronic processes limiting the operation of efficient solar cells with particular emphasis on the role of electronic states endowed with magnetic dipole moment. The research work is divided into two parts. The first part deals...
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High order of nongeminate recombination in organic bulk heterojunction solar cells
PublicationWe analyze high order of nongeminate recombination in organic donor–acceptor bulk heterojunction solar cells. The model of recombination where an exciton annihilates on an electron–hole Langevin bound pair near donor–acceptor interface has been applied in our studies. We obtained satisfactory agreement between experimental results and theoretical calculations for the concentration dependences of several parameters characterizing...
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Four-body recombination in organic bulk heterojunction solar cells: an alternative interpretation
PublicationWe demonstrate a new interpretation of the previously reported quadrimolecular recombination in organic bulk heterojunction solar cells. It is suggested that the recently described (Szmytkowski 2012 Phys. Status Solidi RRL 6 300) interaction between exciton and electron–hole Langevin bound pair formed across the donor–acceptor interface is a four-particle process. This is in opposition to the treatment of this effect as a three-particle...
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Influence of orientational disorder on the optical absorption properties in hybrid metal‐halide perovskite CH3NH3PbI3. A combined DFT/TD‐DFT and experimental study.
PublicationAn experimental and theoretical investigation is reported to analyze the relation between the structural and absorption properties of CH3NH3PbI3 in the tetragonal phase. More than 3000 geometry optimizations were performed in order to reveal the structural disorder and to identify structures with the lowest energies. The electronic structure calculations provide an averaged band gap of 1.674 eV, which is in excellent agreement...
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Crystalline Silicon (c-Si)-Based Tunnel Oxide Passivated Contact (TOPCon) Solar Cells: A Review
PublicationContact selectivity is a key parameter for enhancing and improving the power conversion efficiency (PCE) of crystalline silicon (c-Si)-based solar cells. Carrier selective contacts (CSC) are the key technology which has the potential to achieve a higher PCE for c-Si-based solar cells closer to their theoretical efficiency limit. A recent and state-of-the-art approach in this domain is the tunnel oxide passivated contact (TOPCon)...
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A DFT/TD DFT study of the structure and spectroscopic properties of 5-methyl-2-(8-quinolinyl)benzoxazole and its complexes with Zn(II) ion
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Model-Free Controller Tuning Based on DFT Processing: Application to Induction Motor Drives
PublicationIn this paper, we present a new approach based on discrete Fourier transform (DFT) analysis for controller tuning of the closed-loop system with unknown plant. The DFT analysis is used to process the closed-loop measurements collected online to derive the frequency response of an initial closed-loop system that does not provide a good performance. Based on the closed-loop frequency response data, we propose two methods for tuning PID...
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The photocurrent quantum efficiency dependence on the applied voltage in organic solar cells
PublicationWe demonstrate that our recently reported model (Szmytkowski 2007 J. Phys. D: Appl. Phys. 40 3352) of the photocurrent quantum efficiency in organic semiconductors explains the external quantum efficiency dependence on the electric field in organic solar cells. This effect can be explained by taking into account that the photogeneration of charge carriers occurs via the electron-hole pair dissociation and the space charge effects...
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An analysis of solar energy conversion systems based on photon and thermal processes
PublicationSolar spectral irradiance covers a fairly broad wavelength range. Solar radiation is part of the electromagnetic spectrum which is described by the concept of wave-particle duality. The corpuscular theory of electromagnetic radiation states that energy is transmitted by photons. Photons carry specific amounts of energy which can be used to convert solar energy into other types of energy, in particular electricity. The internal...
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Novel Interpolation Method of Multi-DFT-Bins for Frequency Estimation of Signal with Parameter Step Change
PublicationThe IpDFT(Interpolation Discrete Fourier Trans-form) method is one of the most commonly used non-parametric methods. However, when a parameter (frequency, amplitude or phase) step changes in the DFT period, the DFT coefficients will be distorted seriously, resulting in the large estimation error of the IpDFT method. Hence, it is a key challenge to find an IpDFT method, which not only can eliminate the effect of the step-changed...
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Porównanie metod filtracji w dziedzinie widma DFT
PublicationW niniejszej pracy zaprezentowano porównanie metod filtracji w dziedzinie częstotliwości,czyli w dziedzinie widma DFT. Opisano i omówiono podstawowe metody filtracji: bez zeropaddingu, z zeropaddingiem oraz metodę Cheh Pana. Pokazane i porównane zostały wyniki eksperymentów dla typowych aplikacji, jakimi są filtr dolnoprzepustowy i filtr różniczkujący.
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Understanding the Dominant Physics Mechanisms on the p-i-n Perovskite Solar Cells Fabricated by Scalable Slot-Die Coating Process in Ambient Air
PublicationPerovskite solar cells (PSC) are emerging technologies that have shown continuous improvement in power conversion efficiency (PCE) and stability. However, a very important aspect that has been seldom considered is the reproducibility of PCE of PSC devices. It is possible to achieve PCE from 10.21% to 17.05% using scalable slot-die-coating technique. However, a spatial distribution of performance is clearly observed for device samples...
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Unravelling the role of electron–hole pair spin in exciton dissociation in squaraine-based organic solar cells by magneto-photocurrent measurements
PublicationA high absorption coefficient and narrow absorption bands in squaraine (SQ) dyes have resulted in rapidly growing interest in them as a donor material in photovoltaic devices. The exciton dissociation process in organic systems proceeds via a multistep mechanism where the electron–hole pairs (charge transfer states) involved in the current generation process determine the recombination losses and subsequently limit the overall...
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Simulation investigation of perovskite-based solar cells
PublicationThree models of thin-layer lead-halide perovskite solar cells with different electron-transport layers (TiO2,SnO2,ZnO) were investigatedby the simulation method. The perovskite layer thickness was optimized for all the systems. The analysis of the standard photovoltaic cell performanceparameters at various operating temperatures was performed. The best performance was achieved for the system with theSnO2conductive layer.
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Filtr ułamkowoopóźniający realizowany w dziedzinie transformaty DFT
PublicationW pracy przestawiono zagadnienie implementacji w dziedzinie częstotliwości dyskretnej filtrów o zadanym opóźnieniu ułamkowym.Dla zapewnienia wysokiej jakości implementowanych filtrów konieczne jest jawne określenie prążków charakterystyki częstotliwościowej takiego filtru w jego paśmie niespecyfikowanym. Pokazano, że zaproponowana implementacja w realizowana w dziedzinie transformaty DFT możne zostać powiązana w dziedzinie czasu...
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Impact of the trap–assisted recombination in the perovskite solar cells
PublicationTo achieve the highest performance using perovskite solar cells it is necessary to understand all the dominant mechanisms which affect the operation of solar cell. Here, we have investigated the bulk and interface trap–assisted recombination processes in the solar cells with p–i–n architecture. These studies are based on the numerical and experimental methods to get better understanding of these physical processes. The following results...
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Projektowanie filtru DFT-VFD metodą Hooke-Jeevesa
PublicationZaletą filtrów ułamkowo opóźniających typu DFT-VFD określanych przez współczynniki ich dyskretnej charakterystyki częstotliwościowej z pasma przejściowego jest ich powiązanie z metodą okien przesuwanych. Czyni je to szczególnie przydatnymi w zastosowaniach do zmiany szybkości próbkowania. Problem stanowi jednak projektowanie tych filtrów. Dotychczas dostępna metoda POCS co prawda gwarantuje zbieżność, ale jest ona bardzo powolna....
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Self-Sensitized Photocatalytic Degradation of Colorless Organic Pollutants Attached to Rutile Nanorods—Experimental and Theoretical DFT+D Studies
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Featuring Semitransparent p–i–n Perovskite Solar Cells for High-Efficiency Four-Terminal/Silicon Tandem Solar Cells
PublicationTwo issues need to be resolved when fabricating p–i–n semitransparent perovskite solar cells (ST-PVSCs) for four-terminal (4 T) perovskite/silicon tandem solar cells: 1) damage to the underlying absorber (MAPbI3), electron transporting layer ([6,6]-phenyl-C61-butyric acid methyl ester, PCBM), and work function (WF) modifier (polyethylenimine, PEI), resulting from the harsh sputtering conditions for the transparent electrodes (TEs)...
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Nongeminate recombination in organic bulk heterojunction solar cells: Contribution of exciton–polaron interaction
PublicationA new model to explain nongeminate recombination in organic bulk heterojunction solar cells is presented. We suggest that the annihilation of excitons on charge carriers at the interface between donor and acceptor phases competes with the bimolecular recombination of Coulombically bound electron–hole pairs. The exciton–polaron interaction gives visible contribution to the reduction of Langevin recombination. An analytical formula,...
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Synthesis and Spectroscopic Characterization of Selected Phenothiazines and Phenazines Rationalized Based on DFT Calculation
PublicationTwo unique structures were isolated from the phosphorylation reaction of 10H-phenothiazine.The 5,5-dimethyl-2-(10H-phenothiazin-10-yl)-1,3,2-dioxaphosphinane 2-oxide (2a) illustrates theproduct of N-phosphorylation of phenothiazine. Moreover, a potential product of 2a instability,a thiophosphoric acid 2b, was successfully isolated and structurally characterized. Molecule 2a,similarly to sulfoxide derivative...
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Experimental and DFT insights into an eco-friendly photocatalytic system toward environmental remediation and hydrogen generation based on AgInS2 quantum dots embedded on Bi2WO6
PublicationBismuth tungstate (Bi2WO6) can work as a photocatalyst but suffers from rapid recombination of photogenerated charge carriers. Herein, density functional theory (DFT) simulations revealed that the formation of a thermodynamically stable AgInS2(112)/Bi2WO6(010) heterojunction could promote charge separation and enhance the photoactivity of Bi2WO6. To confirm these theoretical predictions, a new type of photocatalysts in the form...
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Better understanding EMI generation of power converters
PublicationPrzedstawiono metodę przewidywania poziomu zaburzeń w układzie podwyższającym napięcie w oparciu o metodę filtracji Wienera. Pozwoliło to na określenie odpowiedzi impulsowej pomiędzy przyczyną zaburzenia (zmianą napięcia na elementach półprzewdonikowych) a zaburzeniem. Metodę zwerifikowano przy użyciu danych z symulacji oraz pomiarów w rzeczywistym obiekcie
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Effect of band gap on power conversion efficiency of single-junction semiconductor photovoltaic cells under white light phosphor-based LED illumination
PublicationOn the basis of the detailed balance principle, curves of efficiency limit of single-junction photovoltaic cells at warm and cool white light phosphor-based LED bulbs with luminous efficacy exceeding 100 lm/W have been simulated. The effect of energy band gap and illuminance on the efficiencies at warm and cool light is discussed. The simulations carried out show that maximum power conversion efficiency at 1000 lx reaches 52.0%...
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On the tendency of temperature and electric field dependences of interface recombination in P3HT:PCBM organic bulk heterojunction solar cells
PublicationWe demonstrate theoretical explanation of the temperature and electric field dependences of recombination coefficients in an organic P3HT:PCBM bulk heterojunction solar cell. Based onthe model of interface recombination, two analytical formulas describing the relative ratio of the interface (γI ) to the Langevin (γL) recombination coefficients have been derived. Our analysis indicates that the sign of parameters φT and φF determines...
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Analysis of higher recombination orders in organic bulk heterojunction solar cells
PublicationRecently, it has been experimentally demonstrated that an order of nongeminate recombination exceeds two in some types of organic bulk heterojunction donor-acceptor structures. This result is different than for the case of bimolecular recombination described by Langevin theory. Although several theoretical explanations of this effect have been presented, the origin of higher recombination orders is still questionable. In this work,...
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Radix-4 dft butterfly realization with the use of the modified quadratic residue number system
PublicationW pracy zaprezentowano projektowanie i realizację obliczenia motylkowego dft dla podstawy 4 z użyciem zespolonego systemu resztowego (CRNS) i zmodyfikowanego kwadratowego systemu resztowego (MQRNS). System MQRNS oprócz własności dekompozycyjnych pozwala na realizację mnożenia zespolonego przy zastosowaniu trzech mnożeń rzeczywistych. Przedstawiono konwertery wejściowy CRNS/MQRNS i wyjściowy MQRNS/CRNS, mnożenie zespolone w MQRNS,...
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Analysis of the image force effects on the recombination at the donor-acceptor interface in organic bulk heterojunction solar cells
PublicationWe consider the influence of image force effects on the recombination at the donor-acceptor interface in organic bulk heterojunction solar cells. The conclusion is that the charge carriers of one sign located in the material with lower permittivity recombine at the boundary between donor and acceptor phases. This process competes with the recombination of opposite sign charge carriers, leading to the reduction of the Langevin-type...
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Investigations of New Phenothiazine-Based Compounds for Dye-Sensitized Solar Cells with Theoretical Insight
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Radix-4 dft butterfly realization with the use of the modified quadratic residue number system
PublicationW pracy przedstawiono algorytm realizacji mnożenia zespolonego z użyciem zmodyfikowanego kwadratowego zmodyfikowanego systemu liczbowego (mqrns) oraz jego zastosowanie do wykonania obliczenia motylkowego dft dla podstawy 4. pokazano też wstępne rezultaty implementacji w układzie xilinx fpga.
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A DFT+U study of carbon nanotubes under influence of a gate voltage
PublicationA possibility of appearance of antiferromagnetic ordering in armchair carbon nanotubes and graphene is studied using density functional theory within a DFT+U approach. It is shown that the Coulomb repulsion between electrons in the -orbitals of graphene would need to reach a threshold value of ,...
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Alternative Energy: Photovoltaic Solar Cells
PublicationSolar radiation is a fuel for photovoltaic cells and modules, which are a source of electric energy. Viable solar technologies that have been developed in the past are starting to be adopted on a broader and more meaningful global scale across different sectors with ever-increasing market penetration. In this entry, a brief overview of the material properties relevant to solar cell operation, the structure of the solar cell, and electrical...
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New uranium(vi) and isothiouronium complexes: synthesis, crystal structure, spectroscopic characterization and a DFT study
PublicationThe crystal structures of S,S′-2,5-dimethylbenzene-1,4-diylbis(methylisothiouronium) diacetate (1_ac), S,S′-2,5-dimethylbenzene-1,4-diylbis(methylisothiouronium) dichloride (1_Cl), 1_U complex, S,S′-naphthalene-1,4-diylbis(methylisothiouronium) dichloride (2_Cl), and 2_U complex were determined for the first time. The supramolecular structures of the compounds obtained are mainly based on hydrogen bonding and ionic interactions...
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Syntheses, spectroscopic and structural properties of phenoxysilyl compounds: X-ray structures, FT-IR and DFT calculations
PublicationThe reaction of silicon disulfide with alkylphenols leads to tetraphenoxysilane, cyclodisilthiane and silanethiol. The products of the reaction of silicon disulfide with phenols are characterized by FT-IR, NMR, X-ray diffraction and DFT calculations. The intramolecular interactions in the compounds are mainly XH---π (X = C, S) whereas the intermolecular interactions are either very weak CH---π/CH---O contacts found in aryloxysilane...
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Weak hydrogen bonding interaction S-H···O=C studied by FT-IR spectroscopy and DFT calculations
PublicationInteractions between the thiolate group of tri-tert-butoxysilanethiol (TBST) and carbonyl group of acetone are studied with the use of FT-IR spectroscopy and DFT calculations.
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Two-body dissociation of isoxazole following double photoionization – an experimental PEPIPICO and theoretical DFT and MP2 study
PublicationThe dissociative double photoionization of isoxazole molecules has been investigated experimentally and theoretically. The experiment has been carried out in the 27.5–36 eV photon energy range using vacuum ultraviolet (VUV) synchrotron radiation excitation combined with ion time-of-flight (TOF) spectrometry and photoelectron–photoion–photoion coincidence (PEPIPICO) technique. Five wellresolved two-body dissociation channels have...
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Bias-Dependent Dynamics of Degradation and Recovery in Perovskite Solar Cells
PublicationDegradation of perovskite solar cells (PSCs) is often found to be partially or fully reversible when the cells are allowed to recover in the dark. Unlike the dynamics of degradation, knowledge about the dynamics of PSC cell recovery is very limited. Here, we demonstrate that the PSC recovery strongly depends on the electrical bias conditions during the light-induced degradation and that it can be manipulated by applying an external...
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Role of surface recombination in perovskite solar cells at the interface of HTL/CH3NH3PbI3
PublicationIn order to achieve the highest performance of organometal trihalide perovskite solar cells, it is required to recognize the dominant mechanisms which play a key role in a perovskite material. In the following studies, we have focused on the interfacial recombination between the hole transporting layer (HTL) and the perovskite CH3NH3PbI3 in solar cell devices with p–i–n architecture. It has been shown that Cu:NiOx : used as HTL...