ORCID Profile
0000-0002-3146-4372
Current Organisations
CSIRO
,
Queensland University of Technology
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Publisher: AIP Publishing
Date: 03-2022
DOI: 10.1063/5.0083230
Abstract: Direct numerical simulation (DNS) results for turbulent open-channel flow through an idealized sine-generated meander with and without an internal heat source that models radiative heating from above are used to analyze the effect of a very sharp meander configuration and thermal stratification on the turbulence structure in the channel with friction Reynolds number Reτ=200. Spatial distributions of temperature, mean velocities, vorticity, mean-flow kinetic energy, and turbulent kinetic energy (TKE) are presented. In both cases, the cross-sectional motion is characterized by three circulation cells: a center-region cell and two weaker outer bank and inner bank cells. However, there is also a small cell observed near the corner of the channel bed inner bank at the channel outlet and the channel bed outer bank at the channel inlet. The tri-cellular cross-stream motions control the distributions of temperature and kinetic energy. In the stratified case, two separated shear layers (SSLs) are found: the first one is formed before the bend apex, and the second one is observed in the wake after the bend apex. In the neutral case, only the first SSL is observed. Turbulent lification can be seen in both cases however, in the stratified case, the second SSL stretches out to the channel outlet and is introduced back to the channel inlet by an anti-symmetric periodic boundary condition and then follows the outer bank line. The two SSLs converge in the region before the bend apex and lify the turbulence more strongly there than in the neutral case. The turbulence kinetic energy budget terms for the stratified case are analyzed to determine the characteristics of production, dissipation and transport of TKE in thermally stratified meandering flow.
Publisher: Wiley
Date: 15-10-2021
Publisher: Elsevier BV
Date: 04-2022
Publisher: Wiley
Date: 10-06-2021
Abstract: Solution‐processed hybrid organic–inorganic perovskite light‐emitting transistors (PeLETs) suffer from low brightness and environmental instability induced by temperature‐activated trapping, ionic motion, and polarization effects, which so far have been hindering the realization of devices operating at room temperature. Here high quality thermally co‐evaporated methylammonium lead iodide perovskite films are employed to minimize ionic motion and significantly improve the electroluminescence characteristics of the perovskite active layer, enabling stable device operation up to ≈ 310 K. The demonstration of PeLETs operating at and beyond room‐temperature paves the way for practical applications in the rapidly evolving area of solid‐state lighting, active‐matrix displays, and visible light communications.
Publisher: Elsevier BV
Date: 03-2018
Publisher: American Chemical Society (ACS)
Date: 18-01-2022
Abstract: Extending halide perovskites' optoelectronic properties to stimuli-responsive chromism enables switchable optoelectronics, information display, and smart window applications. Here, we demonstrate a band gap tunability (chromism) via crystal structure transformation from three-dimensional FAPbBr
Publisher: Elsevier BV
Date: 10-2015
Publisher: The University of Queensland
Date: 11-12-2020
DOI: 10.14264/0024312
Publisher: Springer Science and Business Media LLC
Date: 05-10-2023
Publisher: Elsevier
Date: 2023
Publisher: CRC Press
Date: 21-07-2017
Publisher: American Chemical Society (ACS)
Date: 02-05-2023
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7TC05033J
Abstract: A study of photocurrent in SQ based solar cells, using a wide range of magnetic fields and temperatures, reveals that depending on the electron acceptor content, the photocurrent generation is limited by dissociation/recombination of e–h pairs or CT states.
Publisher: Springer Science and Business Media LLC
Date: 21-07-2016
DOI: 10.1038/SREP30077
Abstract: The charge recombination and exciton dissociation are generally recognized as the basic electronic processes limiting the efficiency of photovoltaic devices. In this work, we propose a detailed mechanism of photocurrent generation in dye-sensitized solar cells (DSSCs) examined by magnetic field effect (MFE) technique. Here we demonstrate that the magnitude of the MFE on photocurrent in DSSCs can be controlled by the radius and spin coherence time of electron-hole (e-h) pairs which are experimentally modified by the photoanode morphology (TiO 2 nanoparticles or nanotubes) and the electronic orbital structure of various dye molecules (ruthenium N719, dinuclear ruthenium B1 and fully organic squaraine SQ2 dyes). The observed MFE is attributed to magnetic-field-induced spin-mixing of (e-h) pairs according to the Δg mechanism.
Publisher: Elsevier BV
Date: 05-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0NR08093D
Abstract: Demonstration of Rb 2 CuX 3 (X = Br, Cl) colloidal nanocrystals under UV light with a representation of one-dimensional Rb 2 CuBr 3 crystal structure.
Publisher: CRC Press
Date: 02-08-2017
Publisher: American Society of Civil Engineers (ASCE)
Date: 09-2023
Publisher: Wiley
Date: 25-07-2023
Abstract: Unbalanced mobility and injection of charge carriers in metal‐halide perovskite light‐emitting devices pose severe limitations to the efficiency and response time of the electroluminescence. Modulation of gate bias in methylammonium lead iodide light‐emitting transistors has proven effective in increasing the brightness of light emission up to MHz frequencies. In this work, a new approach is developed to improve charge carrier injection and enhance electroluminescence of perovskite light‐emitting transistors by independent control of drain–source and gate–source bias voltages to compensate for space‐charge effects. Optimization of bias pulse synchronization induces a fourfold enhancement of the emission intensity. Interestingly, the optimal phase delay between biasing pulses depends on modulation frequency due to the capacitive nature of the devices, which is well captured by numerical simulations of an equivalent electrical circuit. These results provide new insights into the electroluminescence dynamics of AC‐driven perovskite light‐emitting transistors and demonstrate an effective strategy to optimize device performance through independent control of the litude, frequency, and phase of the biasing pulses.
Publisher: Wiley
Date: 14-02-2022
Abstract: The Rashba effect, i.e., the splitting of electronic spin‐polarized bands in the momentum space of a crystal with broken inversion symmetry, has enabled the realization of spin‐orbitronic devices, in which spins are manipulated by spin–orbit coupling. In optics, where the helicity of light polarization represents the spin degree of freedom for spin–momentum coupling, the optical Rashba effect is manifested by the splitting of optical states with opposite chirality in the momentum space. Previous realizations of the optical Rashba effect relied on passive devices determining the surface plasmon or light propagation inside nanostructures, or the directional emission of chiral luminescence when hybridized with light‐emitting media. An active device underpinned by the optical Rashba effect is demonstrated here, in which a monolithic halide perovskite metasurface emits highly directional chiral photoluminescence. An all‐dielectric metasurface design with broken in‐plane inversion symmetry is directly embossed into the high‐refractive‐index, light‐emitting perovskite film, yielding a degree of circular polarization of photoluminescence of 60% at room temperature.
Publisher: Elsevier BV
Date: 08-2021
Publisher: Elsevier BV
Date: 2014
Publisher: Elsevier BV
Date: 11-2019
Publisher: IEEE
Date: 21-06-2021
Publisher: Research and Innovation Centre Pro-Akademia
Date: 2018
DOI: 10.32933/ACTAINNOVATIONS.26.7
Abstract: The main goal of the study was to investigate the relationship between the orientation of the PVT (PhotoVoltaic Thermal) collector and the thermal and electric power generated. Extensive research was performed to find optimal tilt angles for hybrid solar thermal collectors, which combine photovoltaic as well as thermal collection in a single unit, known as PVT (PhotoVoltaic Thermal) modules for an office building with working hours between 7.00 and 16.00. The comprehensive study included field measurements of the modules in central Poland and tests under AM (air mass) 1.5 conditions in a certified laboratory KEZO (Centre for Energy Conversion and Renewable Resources) Polish Academy of Sciences in Jablonna. Furthermore, a PVT system was investigated using the simulation method based on the dedicated Polysun software. The PV characteristics and efficiency of the PV module and the relation between power or efficiency of the PVT module and incidence angle of solar-irradiance were studied. Optimal work conditions for commercial PVT modules were ascertained. In addition, it was found that the maximum efficiencies of PV module (ηPV), solar thermal-collector (ηc) and PVT hybrid collector (ηPVT) registered under field conditions were higher than the ones measured under laboratory conditions.
Publisher: Wiley
Date: 17-12-2015
Publisher: MDPI AG
Date: 27-04-2020
DOI: 10.3390/MA13092047
Abstract: Pyrolysis of straw pellets and wood strips was performed in a fixed bed reactor. The chars, solid products of thermal degradation, were used as potential materials for activated carbon production. Chemical and physical activation processes were used to compare properties of the products. The chemical activation agent KOH was chosen and the physical activation was conducted with steam and carbon dioxide as oxidising gases. The effect of the activation process on the surface area, pore volume, structure and composition of the biochar was examined. The s les with the highest surface area (1349.6 and 1194.4 m2/g for straw and wood activated carbons, respectively) were obtained when the chemical activation with KOH solution was applied. The s le with the highest surface area was used as an adsorbent for model wastewater contamination removal.
Publisher: Elsevier BV
Date: 12-2017
Publisher: Author(s)
Date: 2019
DOI: 10.1063/1.5092094
Publisher: Wydawnictwo SIGMA-NOT, sp. z.o.o.
Date: 05-06-2018
Publisher: American Chemical Society (ACS)
Date: 16-11-2022
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4CP01923G
Abstract: We report on the preparation method of nanocrystalline titanium dioxide modified with platinum by using nanosecond laser ablation in liquid (LAL).
Publisher: Elsevier BV
Date: 04-2017
Publisher: AIP Publishing
Date: 09-2022
DOI: 10.1063/5.0106526
Abstract: Thermal stratification can lead to the d ing of turbulence, which reduces the mixing of solutes in a fluid body. A series of direct numerical simulation (DNS) solutions sweeping through a range of four different meandering channel curvatures, from a sharp to mild curvature range, are obtained to investigate the effect of curvature on stratification in meandering thermally stratified turbulent open channel flow with an internal heat source that models radiative heating from above. Based on the DNS results, the present paper addresses two issues. First, the influence of changing curvature on the complex bi-cellular pattern of the secondary flow is investigated, including the distribution of the temperature field. Second, the effects of changing curvature on the degree of stratification are analyzed. Stratification can be characterized by the friction Richardson number Riτ and the bulk Richardson number Rib. Stratification can also be viewed in terms of the transfer of energy from mean flow kinetic energy to potential energy via buoyancy fluxes. We study the effect of curvature on stratification by investigating its effect on the friction and bulk Richardson numbers. We also study the transfers between the global potential and kinetic energy reservoirs, including the global available Ea, background Eb, and total potential energy Ep, and the domain-averaged mean kinetic and turbulent kinetic energy. It is found that, in meandering channels, with the increase in curvature, Ep increases and Riτ and Rib decrease, indicating that increasing curvature leads to a decrease in the level of stratification. On the other hand, we also find that a low curvature meandering channel has a higher level of stratification than a straight channel.
Publisher: Wiley
Date: 22-11-2022
Abstract: Metasurfaces supporting optical bound states in the continuum (BICs) are emerging as simple and compact optical cavities to realize polarization-vortex lasers. The winding of the polarization around the singularity defines topological charges which are generally set by the cavity design and cannot be altered without changing geometrical parameters. Here, a subwavelength-thin phase-change halide perovskite BIC metasurface functioning as a tunable polarization vortex microlaser is demonstrated. Upon the perovskite structural phase transitions, both its refractive index and gain vary substantially, inducing reversible and bistable switching between distinct polarization vortexes underpinned by opposite topological charges. Dynamic tuning and switching of the resulting vector beams may find use in microscopy imaging, particle trapping and manipulation, and optical data storage.
Publisher: Optica Publishing Group
Date: 2020
DOI: 10.1364/CLEO_SI.2020.SF3F.5
Abstract: We report the first dielectric perovskite metasurfaces with continuously tenable optical response across the visible spectmm via a small temperatere gradient around room temperature, bearing potential applications in active light-emitting devices and spatial-light-modulators.
Publisher: Elsevier BV
Date: 08-2021
Publisher: Hindawi Limited
Date: 2012
DOI: 10.1155/2012/927407
Abstract: The lanthanide and scandium groups ions (except Pm and Ac) have been used as dopants of TiO 2 film in dye-sensitized solar cells. The X-ray diffraction spectra show that the modification has no influence on the structure of the electrode however, the diffuse reflectance UV-Vis measurements exhibit significant changes in the electronic properties of modified electrodes. The appearance of energy barrier preventing photoexcited electron back-transfer was confirmed for Sc, Ce, Sm, Tb, Ho, Tm, and Lu modified cells. The best photoconversion performance of 8.88 and 8.80% was found for s les modified with Ce and Yb, respectively, and it was greater by 31.4 and 30.2% than that of a unmodified cell.
Publisher: EDP Sciences
Date: 2018
DOI: 10.1051/E3SCONF/20187001019
Abstract: In order to predict solar thermal collector’s performance and optimization of control algorithms, proper mathematical models are necessary. Computer calculation technique provides tools for determination of modern materials impact on improvement of heat transfer inside the collector and minimization of heat loss. Such analysis is impossible by using standard technical datasheet provided by producer or by using empirical formulas. In the paper the authors present a mathematical model of a flat plate solar thermal collector based on the Hottel-Whiller-Bliss equation and criterial formula. The iterative algorithm solved steady state heat transfer equations for a glazed and an unglazed collector. The validation experiment was conducted under class AAA sun simulator for different inlet temperature and solar irradiation values. The unglazed PV/T and glazed solar thermal collectors were tested. For PV/T the relative difference, between measured and computed outlet temperatures, was below 5% and the highest value was reached for the lowest inlet temperature. The validation study showed that the experimental results reached good agreement with simulation predictions. Presented computation algorithm enables to predict influence of geometry changes on collector performance. The model could be used for optimization of the construction without using CFD methods, which need large computation resources.
Publisher: Optica Publishing Group
Date: 2021
DOI: 10.1364/CLEO_SI.2021.STU1C.2
Abstract: We realized all-dielectric halide perovskite metasurfaces with giant chirality. With circular dichroism as high as 16% and excellent luminescence properties, high refractive index halide perovskite metasurfaces rival conventional dielectric platforms for low cost, active metadevices.
Publisher: Wiley
Date: 23-11-2022
Abstract: Emerging immersive visual communication technologies require light sources with complex functionality for dynamic control of polarization, directivity, wavefront, spectrum, and intensity of light. Currently, this is mostly achieved by free space bulk optic elements, limiting the adoption of these technologies. Flat optics based on artificially structured metasurfaces that operate at the sub‐wavelength scale are a viable solution, however, their integration into electrically driven devices remains challenging. Here, a radically new approach to monolithic integration of a dielectric metasurface into a perovskite light‐emitting transistor is demonstrated. It is shown that nanogratings directly structured on top of the transistor channel yield an 8‐fold increase of electroluminescence intensity and dynamic tunability of polarization. This new light‐emitting metatransistor device concept opens unlimited opportunities for light management strategies based on metasurface design and integration.
Publisher: IEEE
Date: 26-06-2023
Publisher: Springer Science and Business Media LLC
Date: 23-03-2022
DOI: 10.1038/S41467-022-29253-0
Abstract: Recent attempts to synthesize hybrid perovskites with large chirality have been h ered by large size mismatch and weak interaction between their structure and the wavelength of light. Here we adopt a planar nanostructure design to overcome these limitations and realize all-dielectric perovskite metasurfaces with giant superstructural chirality. We identify a direct spectral correspondence between the near- and the far- field chirality, and tune the electric and magnetic multipole moments of the resonant chiral metamolecules to obtain large anisotropy factor of 0.49 and circular dichroism of 6350 mdeg. Simulations show that larger area metasurfaces could yield even higher optical activity, approaching the theoretical limits. Our results clearly demonstrate the advantages of nanostructrure engineering for the implementation of perovskite chiral photonic, optoelectronic, and spintronic devices.
Location: Poland
No related grants have been discovered for Maciej Klein.