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BETA
Philippe, Bertrand, Dr.ORCID iD iconorcid.org/0000-0003-2412-8503
Publications (10 of 40) Show all publications
Mussa, A. S., Liivat, A., Marzano, F., Klett, M., Philippe, B., Tengstedt, C., . . . Svens, P. (2019). Fast-charging effects on ageing for energy-optimized automotive LiNi1/3Mn1/3Co1/3O2/graphite prismatic lithium-ion cells. Journal of Power Sources, 422, 175-184
Open this publication in new window or tab >>Fast-charging effects on ageing for energy-optimized automotive LiNi1/3Mn1/3Co1/3O2/graphite prismatic lithium-ion cells
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2019 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 422, p. 175-184Article in journal (Refereed) Published
Abstract [en]

The reactions in energy-optimized 25 Ah prismatic NMC/graphite lithium-ion cell, as a function of fast charging (1C-4C), are more complex than earlier described. There are no clear charging rate dependent trends but rather different mechanisms dominating at the different charging rates. Ageing processes are faster at 3 and 4C charging. Cycling with 3C-charging results in accelerated lithium plating but the 4C-charging results in extensive gas evolution that contribute significantly to the large cell impedance rise. Graphite exfoliation and accelerated lithium inventory loss point to the graphite electrode as the source of the gas evolution. The results are based on careful post-mortem analyses of electrodes using: scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). SEM results show particle cracking independent of the charging rate used for the cycling. XPS and EIS generally indicate thicker surface film and larger impedance, respectively, towards the edge of the jellyrolls. For the intended application of a battery electric inner-city bus using this type of cell, charging rates of 3C and above are not feasible, considering battery lifetime. However, charging rates of 2C and below are too slow from the point of view of practical charging time.

Keywords
Fast charging, Lithium-ion battery, Ageing, Energy battery, Electric vehicle
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-384064 (URN)10.1016/j.jpowsour.2019.02.095 (DOI)000465365900021 ()
Funder
Swedish Energy Agency, P40501-1
Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2019-06-20Bibliographically approved
Jain, S. M., Phuyal, D., Davies, M. L., Li, M., Philippe, B., De Castro, C., . . . Durrant, J. R. (2018). An effective approach of vapour assisted morphological tailoring for reducing metal defect sites in lead-free, (CH3NH3)(3)Bi2I9 bismuth-based perovskite solar cells for improved performance and long-term stability. Nano Energy, 49, 614-624
Open this publication in new window or tab >>An effective approach of vapour assisted morphological tailoring for reducing metal defect sites in lead-free, (CH3NH3)(3)Bi2I9 bismuth-based perovskite solar cells for improved performance and long-term stability
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2018 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 49, p. 614-624Article in journal (Refereed) Published
Abstract [en]

We present a controlled, stepwise formation of methylammonium bismuth iodide (CH3NH3)(3)Bi2I9 perovskite films prepared via the vapour assisted solution process (VASP) by exposing BiI3 films to CH3NH3I (MAI) vapours for different reaction times, (CH3NH3)(3)Bi2I9 semiconductor films with tunable optoelectronic properties are obtained. Solar cells prepared on mesoporous TiO2 substrates yielded hysteresis-free efficiencies upto 3.17% with good reproducibility. The good performance is attributed mainly to the homogeneous surface coverage, improved stoichiometry, reduced metallic content in the bulk, and desired optoelectronic properties of the absorbing material. In addition, solar cells prepared using pure BiI3 films without MAI exposure achieved a power conversion efficiency of 0.34%. The non-encapsulated (CH3NH3)(3)Bi2I9 devices were found to be stable for as long as 60 days with only 0.1% drop in efficiency. This controlled formation of (CH3NH3)(3)Bi2I9 perovskite films highlights the benefit of the VASP technique to optimize material stoichiometry, morphology, solar cell performance, and long-term durability.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2018
Keywords
Vapour assisted solution process (VASP), Lead free perovskite, (CH3NH3)(3)Bi2I9, Morphological tailoring, High resolution X-ray photoelectron (HAXPES) spectroscopy
National Category
Materials Chemistry Condensed Matter Physics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-358277 (URN)10.1016/j.nanoen.2018.05.003 (DOI)000434829500071 ()
Funder
Swedish Research CouncilEU, Horizon 2020, 663830
Available from: 2018-08-27 Created: 2018-08-27 Last updated: 2018-10-26Bibliographically approved
Chernysheva, E., Srour, W., Philippe, B., Baris, B., Chenot, S., Felix Duarte, R., . . . Lazzari, R. (2018). Band alignment at Ag/ZnO(0001) interfaces: A combined soft and hard x-ray photoemission study. Physical Review B, 97(23), Article ID 235430.
Open this publication in new window or tab >>Band alignment at Ag/ZnO(0001) interfaces: A combined soft and hard x-ray photoemission study
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2018 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, no 23, article id 235430Article in journal (Refereed) Published
Abstract [en]

Band alignment at the interface between evaporated silver films and Zn- or O-terminated polar orientations of ZnO is explored by combining soft and hard x-ray photoemissions on native and hydrogenated surfaces. Ultraviolet photoemission spectroscopy (UPS) is used to track variations of work function, band bending, ionization energy, and Schottky barrier during silver deposition. The absolute values of band bending and the bulk position of the Fermi level are determined on continuous silver films by hard x-ray photoemission spectroscopy (HAXPES) through a dedicated modeling of core levels. Hydrogenation leads to the formation of similar to 0.3 monolayer of donorlike hydroxyl groups on both ZnO-O and ZnO-Zn surfaces and to the release of metallic zinc on ZnO-Zn. However, no transition to an accumulation layer is observed. On bare surfaces, silver adsorption is cationic on ZnO(000 (1) over bar)-O [anionic on ZnO(0001)-Zn] at the earliest stages of growth as expected from polarity healing before adsorbing as a neutral species. UPS and HAXPES data appear quite consistent. The two surfaces undergo rather similar band bendings for all types of preparation. The downward band bending of V-bb,(ZnO-O) = -0.4 eV and V-bb,(ZnO-Zn) = -0.6 eV found for the bare surfaces is reinforced upon hydrogenation (V-bb,(ZnO-O+H) = -1.1 eV, V-bb,(ZnO-Zn+H) = -1.2 eV). At the interface with Ag, a unique value of band bending of -0.75 eV is observed. While exposure to atomic hydrogen modulates strongly the energetic positions of the surface levels, a similar Schottky barrier of 0.5-0.7 eV is found for thick silver films on the two surfaces.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-358511 (URN)10.1103/PhysRevB.97.235430 (DOI)000435638500004 ()
Funder
EU, FP7, Seventh Framework Programme, 312284
Available from: 2018-09-03 Created: 2018-09-03 Last updated: 2018-09-03Bibliographically approved
Abdi-Jalebi, M., Pazoki, M., Philippe, B., Dar, M. I., Alsari, M., Sadhanala, A., . . . Friend, R. H. (2018). Dedoping of Lead Halide Perovskites Incorporating Monovalent Cations. ACS Nano, 12(7), 7301-7311
Open this publication in new window or tab >>Dedoping of Lead Halide Perovskites Incorporating Monovalent Cations
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2018 (English)In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 7, p. 7301-7311Article in journal (Refereed) Published
Abstract [en]

We report significant improvements in the optoelectronic properties of lead halide perovskites with the addition of monovalent ions with ionic radii close to Pb2+. We investigate the chemical distribution and electronic structure of solution processed CH3NH3PbI3 perovskite structures containing Na+, Cu+, and Ag+, which are lower valence metal ions than Pb2+ but have similar ionic radii. Synchrotron X-ray diffraction reveals a pronounced shift in the main perovskite peaks for the monovalent cation-based films, suggesting incorporation of these cations into the perovskite lattice as well as a preferential crystal growth in Ag+ containing perovskite structures. Furthermore, the synchrotron X-ray photoelectron measurements show a significant change in the valence band position for Cu- and Ag-doped films, although the perovskite bandgap remains the same, indicating a shift in the Fermi level position toward the middle of the bandgap. Such a shift infers that incorporation of these monovalent cations dedope the n-type perovskite films when formed without added cations. This dedoping effect leads to cleaner bandgaps as reflected by the lower energetic disorder in the monovalent cation-doped perovskite thin films as compared to pristine films. We also find that in contrast to Ag+ and Cu+, Na+ locates mainly at the grain boundaries and surfaces. Our theoretical calculations confirm the observed shifts in X-ray diffraction peaks and Fermi level as well as absence of intrabandgap states upon energetically favorable doping of perovskite lattice by the monovalent cations. We also model a significant change in the local structure, chemical bonding of metal-halide, and the electronic structure in the doped perovskites. In summary, our work highlights the local chemistry and influence of monovalent cation dopants on crystallization and the electronic structure in the doped perovskite thin films.

Keywords
monovalent cations, dedoped perovskite thin films, enhanced optoelectronic quality, substitutional doping, interstitial doping
National Category
Materials Chemistry Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-364505 (URN)10.1021/acsnano.8b03586 (DOI)000440505000097 ()29953817 (PubMedID)
Funder
Swedish Research CouncilSwedish Energy AgencySwedish Foundation for Strategic Research StandUpEU, Horizon 2020, 687008Swedish National Infrastructure for Computing (SNIC), snice 2017-01-15; snice 2016-10-23
Available from: 2018-11-05 Created: 2018-11-05 Last updated: 2019-02-19Bibliographically approved
Cappel, U. B., Liu, P., Johansson, F., Philippe, B., Giangrisostomi, E., Ovsyannikov, R., . . . Rensmo, H. (2018). Electronic Structure Characterization of Cross-Linked Sulfur Polymers. ChemPhysChem, 19(9), 1041-1047
Open this publication in new window or tab >>Electronic Structure Characterization of Cross-Linked Sulfur Polymers
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2018 (English)In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 19, no 9, p. 1041-1047Article in journal (Refereed) Published
Abstract [en]

Cross-linked polymers of elemental sulfur are of potential interest for electronic applications as they enable facile thin-film processing of an abundant and inexpensive starting material. Here, we characterize the electronic structure of a cross-linked sulfur/diisopropenyl benzene (DIB) polymer by a combination of soft and hard X-ray photoelectron spectroscopy (SOXPES and HAXPES). Two different approaches for enhancing the conductivity of the polymer are compared: the addition of selenium in the polymer synthesis and the addition of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) during film preparation. For the former, we observe the incorporation of Se into the polymer structure resulting in a changed valence-band structure. For the latter, a Fermi level shift in agreement with p-type doping of the polymer is observed and also the formation of a surface layer consisting mostly of TFSI anions.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2018
Keywords
cross-linking, hole-transporting material, solar cells, sulfur polymers, X-ray photoelectron spectroscopy
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-356387 (URN)10.1002/cphc.201800043 (DOI)000431492600005 ()29451358 (PubMedID)
Funder
Swedish Research CouncilSwedish Foundation for Strategic Research Swedish Energy AgencySwedish Research Council, 2014-6463StandUp
Available from: 2018-07-25 Created: 2018-07-25 Last updated: 2018-07-25Bibliographically approved
Phuyal, D., Safdari, M., Pazoki, M., Liu, P., Philippe, B., Kvashnina, K. O., . . . Gardner, J. (2018). Electronic Structure of Two-Dimensional Lead(II) Iodide Perovskites: An Experimental and Theoretical Study. Chemistry of Materials, 30(15), 4959-4967
Open this publication in new window or tab >>Electronic Structure of Two-Dimensional Lead(II) Iodide Perovskites: An Experimental and Theoretical Study
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2018 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, no 15, p. 4959-4967Article in journal (Refereed) Published
Abstract [en]

Layered two-dimensional (2D) hybrid organic-inorganic perovskites (HOP) are promising materials for light-harvesting applications because of their chemical stability, wide flexibility in composition and dimensionality, and increases in photovoltaic power conversion efficiencies. Three 2D lead iodide perovskites were studied through various X-ray spectroscopic techniques to derive detailed electronic structures and band energetics profiles at a titania interface. Core-level and valence band photoelectron spectra of HOP were analyzed to resolve the electronic structure changes due to the reduced dimensionality of inorganic layers. The results show orbital narrowing when comparing the HOP, the layered precursor PbI2, and the conventional 3D (CH3NH3)PbI3 such that different localizations of band edge states and narrow band states are unambiguously due to the decrease in dimensionality of the layered HOPs. Support from density functional theory calculations provide further details on the interaction and band gap variations of the electronic structure. We observed an interlayer distance dependent dispersion in the near band edge electronic states. The results show how tuning the interlayer distance between the inorganic layers affects the electronic properties and provides important design principles for control of the interlayer charge transport properties, such as the change in effective charge masses as a function of the organic cation length. The results of these findings can be used to tune layered materials for optimal functionality and new applications.

National Category
Condensed Matter Physics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-361922 (URN)10.1021/acs.chemmater.8b00909 (DOI)000442186500014 ()
Funder
StandUpSwedish Energy AgencySwedish Research CouncilKnut and Alice Wallenberg Foundation
Note

De två första författarna delar förstaförfattarskapet.

Available from: 2018-09-27 Created: 2018-09-27 Last updated: 2018-11-02Bibliographically approved
Jacobsson, J., Svanström, S., Andrei, V., Rivett, J. P. H., Kornienko, N., Philippe, B., . . . Boschloo, G. (2018). Extending the Compositional Space of Mixed Lead Halide Perovskites by Cs, Rb, K, and Na Doping. The Journal of Physical Chemistry C, 122(25), 13548-13557
Open this publication in new window or tab >>Extending the Compositional Space of Mixed Lead Halide Perovskites by Cs, Rb, K, and Na Doping
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2018 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 25, p. 13548-13557Article in journal (Refereed) Published
Abstract [en]

A trend in high performing lead halide perovskite solar cell devices has been increasing compositional complexity by successively introducing more elements, dopants, and additives into the structure; and some of the latest top efficiencies have been achieved with a quadruple cation mixed halide perovskite Cs(x)FA(y)MA(z)Rb(1-x-y-z)PbBr(q)I(3-9). This paper continues this trend by exploring doping of mixed lead halide perovskites, FA(0.83)MA(0.17)PbBr(0.51)I(2.49), with an extended set of alkali cations, i.e., Cs+, Rb+, K+, and Na+, as well as combinations of them. The doped perovskites were investigated with X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, hard X-ray photoelectron spectroscopy, UV-vis, steady state fluorescence, and ultrafast transient absorption spectroscopy. Solar cell devices were made as well. Cs+ can replace the organic cations in the perovskite structure, but Rb+, K+, and Na+ do not appear to do that. Despite this, samples doped with K and Na have substantially longer fluorescence lifetimes, which potentially could be beneficial for device performance.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
National Category
Physical Chemistry Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-361115 (URN)10.1021/acs.jpcc.7b12464 (DOI)000437811500039 ()
Funder
Swedish Energy Agency, P43294-1Swedish Foundation for Strategic Research , RMA15-0130
Available from: 2018-09-21 Created: 2018-09-21 Last updated: 2019-02-18Bibliographically approved
Abdi-Jalebi, M., Andaji-Garmaroudi, Z., Cacovich, S., Stavrakas, C., Philippe, B., Richter, J. M., . . . Stranks, S. D. (2018). Maximizing and stabilizing luminescence from halide perovskites with potassium passivation. Nature, 555, 497-501
Open this publication in new window or tab >>Maximizing and stabilizing luminescence from halide perovskites with potassium passivation
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2018 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 555, p. 497-501Article in journal (Refereed) Published
Abstract [en]

Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability2 (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield—a quantity that must be maximized to obtain high efficiency—remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach the efficiency limits in tandem solar cells, coloured-light-emitting diodes and other optoelectronic applications.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-347206 (URN)10.1038/nature25989 (DOI)000427937900048 ()29565365 (PubMedID)
Funder
EU, European Research Council, 756962EU, FP7, Seventh Framework Programme, PIOF-GA-2013-622630EU, European Research Council, 25961976Swedish Research Council, 20146019
Available from: 2018-03-27 Created: 2018-03-27 Last updated: 2018-05-29Bibliographically approved
Jalebi, M. A., Andaji-Garmaroudi, P., Pearson, A. J., Divitini, G., Cacovich, S., Philippe, B., . . . Stranks, S. D. (2018). Potassium- and Rubidium-Passivated Alloyed Perovskite Films: Optoelectronic Properties and Moisture Stability. ACS ENERGY LETTERS, 3(11), 2671-2678
Open this publication in new window or tab >>Potassium- and Rubidium-Passivated Alloyed Perovskite Films: Optoelectronic Properties and Moisture Stability
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2018 (English)In: ACS ENERGY LETTERS, ISSN 2380-8195, Vol. 3, no 11, p. 2671-2678Article in journal (Refereed) Published
Abstract [en]

Halide perovskites passivated with potassium or rubidium show superior photovoltaic device performance compared to unpassivated samples. However, it is unclear which passivation route is more effective for film stability. Here, we directly compare the optoelectronic properties and stability of thin films when passivating triple-cation perovskite films with potassium or rubidium species. The optoelectronic and chemical studies reveal that the alloyed perovskites are tolerant toward higher loadings of potassium than rubidium. Whereas potassium complexes with bromide from the perovskite precursor solution to form thin surface passivation layers, rubidium additives favor the formation of phase-segregated micron-sized rubidium halide crystals. This tolerance to higher loadings of potassium allows us to achieve superior passivation. We also find that exposure to a humid atmosphere drives phase luminescent properties with potassium segregation and grain coalescence for all compositions, with the rubidium-passivated sample showing the highest sensitivity to nonperovskite phase formation. Our work highlights the benefits but also the limitations of these passivation approaches in maximizing both optoelectronic properties and the stability of perovskite films.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-371401 (URN)10.1021/acsenergylett.8b01504 (DOI)000450374600006 ()
Funder
EU, Horizon 2020, 756962EU, European Research Council, 25961976
Available from: 2018-12-20 Created: 2018-12-20 Last updated: 2019-01-07Bibliographically approved
Phuyal, D., Jain, S. M., Philippe, B., Johansson, M. B., Pazoki, M., Kullgren, J., . . . Rensmo, H. (2018). The electronic structure and band interface of cesium bismuth iodide on a titania heterostructure using hard X-ray spectroscopy. Journal of Materials Chemistry A, 6(20), 9498-9505
Open this publication in new window or tab >>The electronic structure and band interface of cesium bismuth iodide on a titania heterostructure using hard X-ray spectroscopy
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2018 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, no 20, p. 9498-9505Article in journal (Refereed) Published
Abstract [en]

Bismuth halide compounds as a non-toxic alternative are increasingly investigated because of their potential in optoelectronic devices and their rich structural chemistry. Hard X-ray spectroscopy was applied to the ternary bismuth halide Cs3Bi2I9 and its related precursors BiI3 and CsI to understand its electronic structure at an atomic level. We specifically investigated the core levels and valence band using X-ray photoemission spectroscopy (PES), high-resolution X-ray absorption (HERFD-XAS), and resonant inelastic X-ray scattering (RIXS) to get insight into the chemistry and the band edge properties of the two bismuth compounds. Using these element specific X-ray techniques, our experimental electronic structures show that the primary differences between the two bismuth samples are the position of the iodine states in the valence and conduction bands and the degree of hybridization with bismuth lone pair (6s(2)) states. The crystal structure of the two layered quasi-perovskite compounds plays a minor role in modifying the overall electronic structure, with variations in bismuth lone pair states and iodine band edge states. Density Functional Theory (DFT) calculations are used to compare with experimental data. The results demonstrate the effectiveness of hard X-ray spectroscopies to identify element specific bulk electronic structures and their use in optoelectronic devices.

National Category
Materials Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-357561 (URN)10.1039/c8ta00947c (DOI)000433427300020 ()
Funder
Swedish Research Council, 2014-6019Swedish Research Council, 2016-4524Swedish Energy Agency, P43549-1Swedish Foundation for Strategic Research , 15-0130Wallenberg Foundations, 2012.0031StandUp
Available from: 2018-08-20 Created: 2018-08-20 Last updated: 2019-02-19Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-2412-8503

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