| 1. |
- Pettersson, Mariell, 1984, et al.
(författare)
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8-Triazolylpurines: Towards Fluorescent Inhibitors of the MDM2/p53 Interaction
- 2015
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:5
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Tidskriftsartikel (refereegranskat)abstract
- Small molecule nonpeptidic mimics of alpha-helices are widely recognised as protein-protein interaction (PPIs) inhibitors. Protein-protein interactions mediate virtually all important regulatory pathways in a cell, and the ability to control and modulate PPIs is therefore of great significance to basic biology, where controlled disruption of protein networks is key to understanding network connectivity and function. We have designed and synthesised two series of 2,6,9-substituted 8-triazolylpurines as alpha-helix mimetics. The first series was designed based on low energy conformations but did not display any biological activity in a biochemical fluorescence polarisation assay targeting MDM2/p53. Although solution NMR conformation studies demonstrated that such molecules could mimic the topography of an alpha-helix, docking studies indicated that the same compounds were not optimal as inhibitors for the MDM2/p53 interaction. A new series of 8-triazolylpurines was designed based on a combination of docking studies and analysis of recently published inhibitors. The best compound displayed low micromolar inhibitory activity towards MDM2/p53 in a biochemical fluorescence polarisation assay. In order to evaluate the applicability of these compounds as biologically active and intrinsically fluorescent probes, their absorption/emission properties were measured. The compounds display fluorescent properties with quantum yields up to 50%.
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| 2. |
- Fondell, Mattis, 1984-, et al.
(författare)
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Temperature Induced Diffusion of Sn and Si in Hematite and Implications for Photocatalytic Water Splitting Applications
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The performance of Hematite (α-Fe2O3) for the water oxidation step in solar hydrogen production is dependent upon annealing of the material. In this study, these effects are investigated in terms of temperature induced diffusion of Sn and Si from the substrate into thin films of hematite by using hard X-ray photoelectron spectroscopy (HAXPES). Here, HAXPES is used for the first time to characterize a buried interface between a conducting substrate and a nanostructured thin film overlayer by diffusion upon annealing. This process is prototypical for the large class of photoelectrochemical devices that uses indium and fluorine doped tin oxide as substrates where the device is subsequently annealed. Indeed, we observe that: diffusion of Sn and Si is significant, already at 550 °C; the photocatalytic efficiency of the hematite films increased, from low values to 0.23 mA/cm2; annealing in air preserves the hematite phase, while annealing in vacuum induces a phase transition into magnetite, which impairs the photocatalytic performance. The increase in efficiency is explained in terms of an improvement of the quantum efficiency of the oxygen evolution reaction accompanied by a slight improvement in charge carrier transport.
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| 3. |
- Hultqvist, Adam, et al.
(författare)
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SnOx Atomic Layer Deposition on Bare Perovskite-An Investigation of Initial Growth Dynamics, Interface Chemistry, and Solar Cell Performance
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:1, s. 510-522
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Tidskriftsartikel (refereegranskat)abstract
- High-end organic-inorganic lead halide perovskite semitransparent p-i-n solar cells for tandem applications use a phenyl-C-61-butyric acid methyl ester (PCBM)/atomic layer deposition (ALD)-SnOx electron transport layer stack. Omitting the PCBM would be preferred for manufacturing, but has in previous studies on (FA,MA)Pb(Br,I)(3) and (Cs,FA)Pb(Br,I)(3) and in this study on Cs(0)(.0)(5)FA(0.79)MA(0.16)PbBr(0.51)I(2.49) (perovskite) led to poor solar cell performance because of a bias-dependent light-generated current. A direct ALD-SnOx exposure was therefore suggested to form a nonideal perovskite/SnOx interface that acts as a transport barrier for the light-generated current. To further investigate the interface formation during the initial ALD SnOx growth on the perovskite, the mass dynamics of monitor crystals coated by partial p-i-n solar cell stacks were recorded in situ prior to and during the ALD using a quartz crystal microbalance. Two major finds were made. A mass loss was observed prior to ALD for growth temperatures above 60 degrees C, suggesting the decomposition of the perovskite. In addition, a mostly irreversible mass gain was observed during the first exposure to the Sn precursor tetrakis(dimethylamino)tin(IV) that is independent of growth temperature and that disrupts the mass gain of the following 20-50 ALD cycles. The chemical environments of the buried interface were analyzed by soft and hard X-ray photoelectron spectroscopy for a sample with 50 ALD cycles of SnOx on the perovskite. Although measurements on the perovskite bulk below and the SnOx film above did not show chemical changes, additional chemical states for Pb, Br, and N as well as a decrease in the amount of I were observed in the interfacial region. From the analysis, these states and not the heating of the perovskite were concluded to be the cause of the barrier. This strongly suggests that the detrimental effects can be avoided by controlling the interfacial design.
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| 4. |
- Jacobsson, Jesper, 1984-, et al.
(författare)
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An open-access database and analysis tool for perovskite solar cells based on the FAIR data principles
- 2022
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Ingår i: Nature Energy. - : Springer Nature. - 2058-7546. ; 7:1, s. 107-115
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Tidskriftsartikel (refereegranskat)abstract
- Large datasets are now ubiquitous as technology enables higher-throughput experiments, but rarely can a research field truly benefit from the research data generated due to inconsistent formatting, undocumented storage or improper dissemination. Here we extract all the meaningful device data from peer-reviewed papers on metal-halide perovskite solar cells published so far and make them available in a database. We collect data from over 42,400 photovoltaic devices with up to 100 parameters per device. We then develop open-source and accessible procedures to analyse the data, providing examples of insights that can be gleaned from the analysis of a large dataset. The database, graphics and analysis tools are made available to the community and will continue to evolve as an open-source initiative. This approach of extensively capturing the progress of an entire field, including sorting, interactive exploration and graphical representation of the data, will be applicable to many fields in materials science, engineering and biosciences.
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| 5. |
- Jacobsson, Jesper, 1984-, et al.
(författare)
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Extending the Compositional Space of Mixed Lead Halide Perovskites by Cs, Rb, K, and Na Doping
- 2018
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 122:25, s. 13548-13557
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Jacobsson, Jesper, 1984-
(författare)
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Photoelectrochemical water splitting : an idea heading towards obsolescence?
- 2018
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Ingår i: Energy & Environmental Science. - : ROYAL SOC CHEMISTRY. - 1754-5692 .- 1754-5706. ; 11:8, s. 1977-1979
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Forskningsöversikt (refereegranskat)abstract
- The production of hydrogen from water and sunlight is a way to address the intermittency in renewable energy production, while simultaneously generating a versatile fuel and a valuable chemical feedstock. Photoelectrochemical water splitting is one possible approach to accomplish this that has been researched since the early seventies. It has for a long time held the promise of having the potential to become the best, cheapest, and most efficient way to convert solar energy into chemical energy in the form of hydrogen, but in this paper, I argue that the time window where this could have happened has now come to an end. With the rapid development of both PV-technology and earth-abundant electrocatalysis, it will be tremendously difficult, even in the best-case scenario, for a classical photoelectrochemical water splitting device to compete with what PV-driven electrolysers can already do today. This is an insight that should influence the future of solar fuel research.
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| 7. |
- Jacobsson, Jesper, 1984-
(författare)
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ZnO Quantum Dots : Size Dependent Optical, Vibrational and Photoelectrochemical Properties
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is devoted to quantum dots of ZnO in the size regime 2.5-10 nm.The focus is directed towards their size dependent properties with specialemphasis on the optical, vibrational and photocatalytic properties. The particleswere synthesized by hydrolysis in alkaline zinc acetate solution.Analysis and characterisation were performed on both growing particles insolution as well as on thin particle films. The main characterisation techniqueswere UV-vis, florescence, XRD, Raman, electrochemical- and photoelectrochemicalmethods.Based on a large set of XRD and UV-vis measurements an empirical relationbetween the band gap and the particle size were developed. This enabledsize resolved measurements of the visible fluorescence on growing particlesin solution. We report evidence of mobile trap states responsible for the fluorescenceand discuss a possible surface dependent mechanism for this.The quantum confinement of the phonon modes were investigated withRaman spectroscopy and molecular dynamic simulations. We report on asize depended suppression of the phonon modes and the contribution fromsurface effects.The absolute position of the conduction band edge was determined as afunction of particle size with different photoelectrochemical methods that wedescribe in detail. We demonstrate that most of the size dependent shift inthe band gap occurs by a change in the position of the conduction band. Wealso show that the parabolic band approximation is valid in a region ofslightly less than 0.1 eV from the conduction band edge, and this even underan external electric field. An interesting electroabsorption phenomenonwhere the absorption locally increases under an applied potential are describedand explained in terms of the quantum confined Stark effect and theFranz-Keldysh effect.The produced films of the particles show antireflective properties on conductingglass substrates, which could be interesting from a technologicalperspective. The films are demonstrated to show photocatalytic activity withrespect to degradation of organic dyes and for solar water splitting.
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| 8. |
- Jacobsson, T. Jesper, 1984-, et al.
(författare)
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2-Terminal CIGS-perovskite tandem cells : A layer by layer exploration
- 2020
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Ingår i: Solar Energy. - : Elsevier BV. - 0038-092X .- 1471-1257. ; 207, s. 270-288
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Tidskriftsartikel (refereegranskat)abstract
- This paper focuses on the development of 2-terminal CIGS-perovskite tandem solar cells by exploring a range of stack sequences and synthetic procedures for depositing the associated layers. In the end, we converged at a stack sequence composed of SLG/Mo/CIGS/CdS/i-ZnO/ZnO:Al/NiO/PTAA/Perovskite/LiF/PCBM/SnO2/ITO. With this architecture, we reached performances only about 1% lower than the corresponding 4-terminal tandem cells, thus demonstrating functional interconnects between the two sub-cells while grown monolithically on top of each other. We go through the stack, layer-by-layer, discussing their deposition and the results, from which we can conclude what works, what does not work, and what potentially could work after additional modifications. The challenges for a successful 2-terminal tandem device include: how to deal with, or decrease, the surface roughness of the CIGS-stack, how to obtain uniform coverage of the layers between the CIGS and the perovskite while also obtaining a benign interface chemistry, and how to tune the band gaps of both the CIGS and the perovskite to obtain good optical matching. The investigation was based on CIGS with a power conversion efficiency around 14%, and perovskites with an efficiency around 12%, resulting in 2-terminal tandem cells with efficiencies of 15–16%. The results indicate that by using higher performing CIGS and perovskite sub-cells, it should be possible to manufacture highly efficient 2-terminal CIGS-perovskite tandem devices by using the protocols, principles, and procedures developed and discussed in this paper.
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| 9. |
- Jacobsson, T. Jesper, 1984-
(författare)
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Highly Efficient CIGS Based Devices for Solar Hydrogen Production and Size Dependent Properties of ZnO Quantum Dots
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Materials and device concepts for renewable solar hydrogen production, and size dependent properties of ZnO quantum dots are the two main themes of this thesis.ZnO particles with diameters less than 10 nm, which are small enough for electronic quantum confinement, were synthesized by hydrolysis in alkaline zinc acetate solutions. Properties investigated include: the band gap - particle size relation, phonon quantum confinement, visible and UV-fluorescence as well as photocatalytic performance. In order to determine the absolute energetic position of the band edges and the position of trap levels involved in the visible fluorescence, methods based on combining linear sweep voltammetry and optical measurements were developed.The large band gap of ZnO prevents absorption of visible light, and in order to construct devices capable of utilizing a larger part of the solar spectrum, other materials were also investigated, like hematite , Fe2O3, and CIGS, CuIn1-xGaxSe2.The optical properties of hematite were investigated as a function of film thickness on films deposited by ALD. For films thinner than 20 nm, a blue shift was observed for both the absorption maximum, the indirect band gap as well as for the direct transitions. The probability for the indirect transition decreased substantially for thinner films due to a suppressed photon/phonon coupling. These effects decrease the visible absorption for films thin enough for effective charge transport in photocatalytic applications.CIGS was demonstrated to be a highly interesting material for solar hydrogen production. CIGS based photocathodes demonstrated high photocurrents for the hydrogen evolution half reaction. The electrode stability was problematic, but was solved by introducing a modular approach based on spatial separation of the basic functionalities in the device. To construct devices capable of driving the full reaction, the possibility to use cells interconnected in series as an alternative to tandem devices were investigated. A stable, monolithic device based on three CIGS cells interconnected in series, reaching beyond 10 % STH-efficiency, was finally demonstrated. With experimental support from the CIGS-devices, the entire process of solar hydrogen production was reviewed with respect to the underlying physical processes, with special focus on the similarities and differences between various device concepts.
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| 10. |
- Jõgi, Indrek, et al.
(författare)
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On the Structural and Optical Properties of Ultrathin Iron Oxide
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Nanostructured iron oxides and especially hematite are interesting for a wide range of applications ranging from gas sensors to renewable solar hydrogen production. A promising method for deposition of low dimensional films is atomic layer deposition, ALD. Although a potent technique, ALD of ultrathin films is sensitive to the substrate and temperature conditions where initial formation of islands and crystallites influences the properties of the films. In this work the optical and structural properties of iron oxide films in the thickness range of 6 nm to 50 nm have been investigated. Below 10 nm nominal film thickness we find island formation and phase dependent particle crystallization that impose difficulties for ALD deposition of phase pure iron oxides on non-lattice matching substrates. For films between 10-20 nm, post-annealing steps were found to be needed to recrystallize iron polymorphs to hematite whereas for films thicker than 20 nm, phase pure hematite can be formed directly with ALD with very low influence of the substrate. Analysis of the indirect and direct band gaps of the thinnest films show a quantum confined blue shift of the absorption edge.
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| 11. |
- Pazoki, Meysam, et al.
(författare)
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Photon Energy-Dependent Hysteresis Effects in Lead Halide Perovskite Materials
- 2017
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:47, s. 26180-26187
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Tidskriftsartikel (refereegranskat)abstract
- Lead halide perovskites have a range of spectacular properties and interesting phenomena and are a serious candidate for the next generation of photovoltaics with high efficiencies and low fabrication costs. An interesting phenomenon is the anomalous hysteresis often seen in current-voltage scans, which complicates accurate performance measurements but has also been explored to obtain a more comprehensive understanding of the device physics. Herein, we demonstrate a wavelength and illumination intensity dependency of the hysteresis in state-of-the-art perovskite solar cells with 18% power conversion efficiency (PCE), which gives new insights into ion migration. The perovskite devices show lower hysteresis under illumination with near band edge (red) wavelengths compared to more energetic (blue) excitation. This can be rationalized with thermalization-assisted ion movement or thermalization-assisted vacancy generation. These explanations are supported by the dependency of the photovoltage decay with illumination time and excitation wavelength, as well as by impedance spectroscopy. The suggested mechanism is that high-energy photons create hot charge carriers that either through thermalization can create additional vacancies or by release of more energetic phonons play a role in overcoming the activation energy for ion movement. The excitation wavelength dependency of the hysteresis presented here gives valuable insights into the photophysics of the lead halide perovskite solar cells.
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| 12. |
- Philippe, Bertrand, Dr. 1986-, et al.
(författare)
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Valence Level Character in a Mixed Perovskite Material and Determination of the Valence Band Maximum from Photoelectron Spectroscopy : Variation with Photon Energy
- 2017
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 121:48, s. 26655-26666
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Tidskriftsartikel (refereegranskat)abstract
- A better understanding of the electronic structure of perovskite materials used in photovoltaic devices is essential for their development and optimization. In this investigation, synchrotron-based photoelectron spectroscopy (PES) was used to experimentally delineate the character and energy position of the valence band structures of a mixed perovskite. The valence band was measured using PES with photon energies ranging from ultraviolet photoelectron spectroscopy (21.2 eV) to hard X-rays (up to 4000 eV), and by taking the variation of the photoionization cross sections into account, we could experimentally determine the inorganic and organic contributions. The experiments were compared to theoretical calculations to further distinguish the role of the different anions in the electronic structure. This work also includes a thorough study of the valence band maximum and its position in relation to the Fermi level, which is crucial for the design and optimization of complete solar cells and their functional properties.
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| 13. |
- Svanström, Sebastian, et al.
(författare)
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Degradation Mechanism of Silver Metal Deposited on Lead Halide Perovskites
- 2020
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 12:6, s. 7212-7221
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 14. |
- Svanström, Sebastian, et al.
(författare)
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Effect of halide ratio and Cs+ addition on the photochemical stability of lead halide perovskites
- 2018
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Ingår i: Journal of Materials Chemistry A. - 2050-7488 .- 2050-7496. ; 6:44, s. 22134-22144
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Tidskriftsartikel (refereegranskat)abstract
- Lead halide perovskite solar cells with multi-cation/mixed halide materials now give power conversion efficiencies of more than 20%. The stability of these mixed materials has been significantly improved through the addition of Cs+ compared to the original methylammonium lead iodide. However, it remains one of the most significant challenges for commercialisation. In this study, we use photoelectron spectroscopy (PES) in combination with visible laser illumination to study the photo-stability of perovskite films with different compositions. These include Br : I ratios of 50 : 50 and 17 : 83 and compositions with and without Cs+. For the samples without Cs and the 50 : 50 samples, we found that the surface was enriched in Br and depleted in I during illumination and that some of the perovskite decomposed into Pb0, organic halide salts, and iodine. After illumination, both of these reactions were partially reversible. Furthermore, the surfaces of the films were enriched in organic halide salts indicating that the cations were not degraded into volatile products. With the addition of Cs+ to the samples, photo-induced changes were significantly suppressed for a 50 : 50 bromide to iodide ratio and completely suppressed for perovskites with a 17 : 83 ratio at light intensities exceeding 1 sun equivalent.
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