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Svanström, S., Jacobsson, J., Boschloo, G., Johansson, E., Rensmo, H. & Cappel, U. B. (2020). Degradation Mechanism of Silver Metal Deposited on Lead Halide Perovskites. ACS Applied Materials and Interfaces, 12(6), 7212-7221
Open this publication in new window or tab >>Degradation Mechanism of Silver Metal Deposited on Lead Halide Perovskites
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2020 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 12, no 6, p. 7212-7221Article in journal (Refereed) Published
Abstract [en]

Lead halide perovskite solar cells have significantly increased in both efficiency and stability over the last decade. An important aspect of their longterm stability is the reaction between the perovskite and other materials in the solar cell. This includes the contact materials and their degradation if they can potentially come into contact through, e.g., pinholes or material diffusion and migration. Here, we explore the interactions of silver contacts with lead halide perovskites of different compositions by using a model system where thermally evaporated silver was deposited directly on the surface of the perovskites. Using X-ray photoelectron spectroscopy with support from scanning electron microscopy, X-ray diffraction, and UV-visible absorption spectroscopy, we studied the film formation and degradation of silver on perovskites with different compositions. The deposited silver does not form a continuous silver film but instead tends to form particles on a bare perovskite surface. These particles are initially metallic in character but degrade into AgI and AgBr over time. The degradation and migration appear unaffected by the replacement of methylammonium with cesium but are significantly slowed down by the complete replacement of iodide with bromide. The direct contact between silver and the perovskite also significantly accelerates the degradation of the perovskite, with a significant loss of organic cations and the possible formation of PbO, and, at the same time, changed the surface morphology of the iodide-rich perovskite interface. Our results further indicate that an important degradation pathway occurred through gas-phase perovskite degradation products. This highlights the importance of control over the interface materials and the use of completely hermetical barrier layers for the long-term stability and therefore the commercial viability of silver electrodes.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2020
Keywords
perovskite solar cells, electrode stability, X-ray photoelectron spectroscopy, interface chemistry, noble metal electrodes
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-407282 (URN)10.1021/acsami.9b20315 (DOI)000514256400040 ()31958007 (PubMedID)
Funder
Swedish Research Council, VR 2018-04125Swedish Research Council, 2018-06465Swedish Research Council, 2018-04330Swedish Foundation for Strategic Research , RMA15-0130Swedish Energy Agency, P43549-1StandUpÅForsk (Ångpanneföreningen's Foundation for Research and Development)Göran Gustafsson Foundation for Research in Natural Sciences and Medicine
Available from: 2020-03-23 Created: 2020-03-23 Last updated: 2020-03-23Bibliographically approved
Wu, H., Zhu, H., Erbing, A., Johansson, M. B., Mukherjee, S., Man, G., . . . Johansson, E. (2019). Bandgap Tuning of Silver Bismuth Iodide via Controllable Bromide Substitution for Improved Photovoltaic Performance. ACS APPLIED ENERGY MATERIALS, 2(8), 5356-5362
Open this publication in new window or tab >>Bandgap Tuning of Silver Bismuth Iodide via Controllable Bromide Substitution for Improved Photovoltaic Performance
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2019 (English)In: ACS APPLIED ENERGY MATERIALS, ISSN 2574-0962, Vol. 2, no 8, p. 5356-5362Article in journal (Refereed) Published
Abstract [en]

In this work, silver-bismuth-halide thin films, exhibiting low toxicity and good stability, were explored systemically by gradually substituting iodide, I, with bromide, Br, in the AgBi2I7 system. It was found that the optical bandgap can be tuned by varying the I/Br ratio. Moreover, the film quality was improved when introducing a small amount of Br. The solar cell was demonstrated to be more stable at ambient conditions and most efficient when incorporating 10% Br, as a result of decreased recombination originating from the increased grain size. Thus, replacing a small amount of I with Br was beneficial for photovoltaic performance.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
Keywords
lead-free solar cells, power conversion efficiency, bandgap, silver bismuth iodide, mixed-halide composition, grain size, density functional theory
National Category
Physical Chemistry Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-391056 (URN)10.1021/acsaem.9b00914 (DOI)000483434700003 ()
Funder
Swedish Research CouncilSwedish Energy AgencyCarl Tryggers foundation
Available from: 2019-08-18 Created: 2019-08-18 Last updated: 2019-12-18Bibliographically approved
Johansson, M. B., Philippe, B., Banerjee, A., Phuyal, D., Mukherjee, S., Chakraborty, S., . . . Johansson, E. (2019). Cesium Bismuth Iodide Solar Cells from Systematic Molar Ratio Variation of CsI and BiI3. Inorganic Chemistry, 58(18), 12040-12052
Open this publication in new window or tab >>Cesium Bismuth Iodide Solar Cells from Systematic Molar Ratio Variation of CsI and BiI3
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2019 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 58, no 18, p. 12040-12052Article in journal (Refereed) Published
Abstract [en]

Metal halide compounds with photovoltaic properties prepared from solution have received increased attention for utilization in solar cells. In this work, low-toxicity cesium bismuth iodides are synthesized from solution, and their photovoltaic and, optical properties as well as electronic and crystal structures are investigated. The X-ray diffraction patterns reveal that a CsI/BiI3 precursor ratio of 1.5:1 can convert pure rhombohedral BiI3 to pure hexagonal Cs3Bi2I9, but any ratio intermediate of this stoichiometry and pure BiI3 yields a mixture containing the two crystalline phases Cs3Bi2I9 and BiI3, with their relative fraction depending on the CsI/BiI3 ratio. Solar cells from the series of compounds are characterized, showing the highest efficiency for the compounds with a mixture of the two structures. The energies of the valence band edge were estimated using hard and soft X-ray photoelectron spectroscopy for more bulk and surface electronic properties, respectively. On the basis of these measurements, together with UV-vis-near-IR spectrophotometry, measuring the band gap, and Kelvin probe measurements for estimating the work function, an approximate energy diagram has been compiled clarifying the relationship between the positions of the valence and conduction band edges and the Fermi level.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-395308 (URN)10.1021/acs.inorgchem.9b01233 (DOI)000486565600024 ()31483638 (PubMedID)
Funder
Swedish Energy AgencySwedish Research CouncilSwedish Research Council FormasSwedish Foundation for Strategic Research
Available from: 2019-10-18 Created: 2019-10-18 Last updated: 2019-10-18Bibliographically approved
Jana, S., Panda, S. K., Phuyal, D., Pal, B., Mukherjee, S., Dutta, A., . . . Sarma, D. D. (2019). Charge disproportionate antiferromagnetism at the verge of the insulator-metal transition in doped LaFeO3. Physical Review B, 99(7), Article ID 075106.
Open this publication in new window or tab >>Charge disproportionate antiferromagnetism at the verge of the insulator-metal transition in doped LaFeO3
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2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 7, article id 075106Article in journal (Refereed) Published
Abstract [en]

We explore the effects of electron doping in lanthanum ferrite, LaFeO3 by doping Mo at the Fe sites. Based on magnetic, transport, scanning tunneling spectroscopy, and x-ray photoelectron spectroscopy measurements, we find that the large gap, charge-transfer, antiferromagnetic (AFM) insulator LaFeO3 becomes a small gap AFM band insulator at low Mo doping. With increasing doping concentration, Mo states, which appear around the Fermi level, is broadened and become gapless at a critical doping of 20%. Using a combination of calculations based on density functional theory plus Hubbard U (DFT+U) and x-ray absorption spectroscopy measurements, we find that the system shows charge disproportionation (CD) in Fe ions at 25% Mo doping, where two distinct Fe sites, having Fe2+ and Fe3+ nominal charge states appear. A local breathing-type lattice distortion induces the charge disproportionation at the Fe site without destroying the antiferromagnetic order. Our combined experimental and theoretical investigations establish that the Fe states form a CD antiferromagnet at 25% Mo doping, which remains insulating, while the appearance of Mo states around the Fermi level is showing an indication towards the insulator-metal transition.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-378537 (URN)10.1103/PhysRevB.99.075106 (DOI)000458168300001 ()
Funder
Swedish Research Council, 2016-4524Knut and Alice Wallenberg Foundation, 2012.0031Swedish Energy Agency, P43294-1EU, European Research Council, CorrelMat-617196Swedish Research Council, 2016-03278Swedish Research CouncilSwedish Foundation for Strategic Research Carl Tryggers foundation , CTS-17:376eSSENCE - An eScience CollaborationStandUp
Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-03-21Bibliographically approved
Massel, F., Hikima, K., Rensmo, H., Suzuki, K., Hirayama, M., Xu, C., . . . Duda, L. (2019). Excess lithium in transition metal layers of epitaxially grown thin film cathodes of Li2MnO3 leads to rapid loss of covalency during first battery cycle. The Journal of Physical Chemistry C, 123(47), 28519-28526
Open this publication in new window or tab >>Excess lithium in transition metal layers of epitaxially grown thin film cathodes of Li2MnO3 leads to rapid loss of covalency during first battery cycle
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2019 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 47, p. 28519-28526Article in journal (Refereed) Published
Abstract [en]

We have investigated the initial-cycle battery behavior of epitaxial thin films of Li2MnO3-cathodes by employing resonant inelastic X-ray scattering (RIXS) at the O K- and Mn L3-edges. Thin films (25 nm thickness) with Li/Mn-ratios of 2.06 (stoichiometric) and 2.27 (over-stoichiometric), respectively, were epitaxially grown by pulsed laser deposition and electrochemically cycled as battery cathodes in half-cell setup, stopped at potentials for full charge (delithiation) and complete discharge (relithiation), respectively, for X-ray analysis. Using RIXS, we find that significant anionic reactions take place in both materials upon initial delithiation. However, no signatures of localized oxygen holes are found in O K-RIXS of the Li2MnO3 regardless of Li/Mn-ratio. Instead, the top of the oxygen valence band is depleted of electrons forming delocalized empty states upon delithiation. Mn L-RIXS of the over-stoichiometric cathode material shows a progressive loss of charge transfer state intensity during the first battery cycle, revealing a more rapid loss of Mn--O covalency in the over-stoichiometric material.

Keywords
Li-ion battery, Li-rich lithium manganese oxide cathode, pulsed laser deposition (PLD), thin film, resonant inelastic X-ray scattering (RIXS), soft X-ray absorption spectroscopy (XAS)
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-390620 (URN)10.1021/acs.jpcc.9b06246 (DOI)000500417600001 ()
Funder
Swedish Research Council, 2014-6019Swedish Research Council, 2016-03545Swedish Research Council, 2018-06465StandUpSwedish Energy Agency, 40495-1
Available from: 2019-08-12 Created: 2019-08-12 Last updated: 2019-12-20Bibliographically approved
Phuyal, D., Mukherjee, S., Jana, S., Denoel, F., Kamalakar, M. V., Butorin, S. M., . . . Karis, O. (2019). Ferroelectric properties of BaTiO3 thin films co-doped with Mn and Nb. AIP Advances, 9(9), Article ID 095207.
Open this publication in new window or tab >>Ferroelectric properties of BaTiO3 thin films co-doped with Mn and Nb
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2019 (English)In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 9, no 9, article id 095207Article in journal (Refereed) Published
Abstract [en]

We report on properties of BaTiO3 thin films where the bandgap is tuned via aliovalent doping of Mn and Nb ions co-doped at the Ti site. The doped films show single-phase tetragonal structure, growing epitaxially with a smooth interface to the substrate. Using piezoforce microscopy, we find that both doped and undoped films exhibit good ferroelectric response. The piezoelectric domain switching in the films was confirmed by measuring local hysteresis of the polarization at several different areas across the thin films, demonstrating a switchable ferroelectric state. The doping of the BaTiO3 also reduces the bandgap of the material from 3.2 eV for BaTiO3 to nearly 2.7 eV for the 7.5% doped sample, suggesting the viability of the films for effective light harvesting in the visible spectrum. The results demonstrate co-doping as an effective strategy for bandgap engineering and a guide for the realization of visible-light applications using its ferroelectric properties.

Place, publisher, year, edition, pages
American Institute of Physics, 2019
Keywords
ferroelectric, complex oxides
National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-393045 (URN)10.1063/1.5118869 (DOI)000488516200011 ()
Funder
Swedish Research Council, 2018-04330Swedish Research Council, 2016-4524Knut and Alice Wallenberg Foundation, 2012.0031Carl Tryggers foundation , CTS-17:376Swedish Energy Agency, P43549-1
Available from: 2019-09-13 Created: 2019-09-13 Last updated: 2019-11-06Bibliographically approved
Maibach, J., Källquist, I., Andersson, M., Urpelainen, S., Edström, K., Rensmo, H., . . . Hahlin, M. (2019). Probing a battery electrolyte drop with ambient pressure photoelectron spectroscopy. Nature Communications, 10, Article ID 3080.
Open this publication in new window or tab >>Probing a battery electrolyte drop with ambient pressure photoelectron spectroscopy
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2019 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 3080Article in journal (Refereed) Published
Abstract [en]

Operando ambient pressure photoelectron spectroscopy in realistic battery environments is a key development towards probing the functionality of the electrode/electrolyte interface in lithium-ion batteries that is not possible with conventional photoelectron spectroscopy. Here, we present the ambient pressure photoelectron spectroscopy characterization of a model electrolyte based on 1M bis(trifluoromethane)sulfonimide lithium salt in propylene carbonate. For the first time, we show ambient pressure photoelectron spectroscopy data of propylene carbonate in the liquid phase by using solvent vapor as the stabilizing environment. This enables us to separate effects from salt and solvent, and to characterize changes in electrolyte composition as a function of probing depth. While the bulk electrolyte meets the expected composition, clear accumulation of ionic species is found at the electrolyte surface. Our results show that it is possible to measure directly complex liquids such as battery electrolytes, which is an important accomplishment towards true operando studies.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2019
National Category
Physical Chemistry Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-390789 (URN)10.1038/s41467-019-10803-y (DOI)000475295300002 ()31300638 (PubMedID)
Funder
Swedish Research Council, 2016-03545Swedish Research Council, 2012-4681Swedish Research Council, 2014-6019Swedish Research Council, 2018-06465Swedish Energy Agency, 40495-1StandUpCarl Tryggers foundation
Available from: 2019-08-15 Created: 2019-08-15 Last updated: 2020-02-24Bibliographically approved
Zhang, X., Cappel, U. B., Jia, D., Zhou, Q., Du, J., Sloboda, T., . . . Johansson, E. (2019). Probing and Controlling Surface Passivation of PbS Quantum Dot Solid for Improved Performance of Infrared Absorbing Solar Cells. Chemistry of Materials, 31(11), 4081-4091
Open this publication in new window or tab >>Probing and Controlling Surface Passivation of PbS Quantum Dot Solid for Improved Performance of Infrared Absorbing Solar Cells
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2019 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 11, p. 4081-4091Article in journal (Refereed) Published
Abstract [en]

Surface properties of colloidal quantum dots (CQDs) are critical for the transportation and recombination of the photoinduced charge carrier in CQD solar cells, therefore dominating the photovoltaic performance. Herein, PbS CQD passivated using liquid-state ligand exchange (LSLX) and solid-state ligand exchange (SSLX) strategies are in detail investigated using photoelectron spectroscopy (PES), and solar cell devices are prepared to understand the link between the CQD surface properties and the solar cell function. PES using different energies in the soft and hard Xray regime is applied to study the surface and bulk properties of the CQDs, and the results show more effective surface passivation of the CQDs prepared with the LSLX strategy and less formation of lead-oxide. The CQD solar cells prepared with LSLX strategy show higher performance, and the photoelectric measurements suggest that the recombination of photoinduced charges is reduced for the solar cell prepared with the LSLX approach. Meanwhile, the fabricated solar cells exhibit good stability. This work provides important insights into how to fine-tune the CQD surface properties by improving the CQD passivation, and how this is linked to further improvements of the device photovoltaic performance.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Materials Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-390215 (URN)10.1021/acs.chemmater.9b00742 (DOI)000471728200026 ()
Funder
Swedish Energy AgencySwedish Research Council FormasSwedish Research CouncilGöran Gustafsson Foundation for Research in Natural Sciences and MedicineStiftelsen Olle Engkvist ByggmästareÅForsk (Ångpanneföreningen's Foundation for Research and Development)
Available from: 2019-08-08 Created: 2019-08-08 Last updated: 2019-08-08Bibliographically 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
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ORCID iD: ORCID iD iconorcid.org/0000-0001-5949-0997

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