| 1. |
- Becker, Pascal, et al.
(författare)
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Low Temperature Synthesis of Stable γ-CsPbI 3 Perovskite Layers for Solar Cells Obtained by High Throughput Experimentation
- 2019
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 9:22
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Tidskriftsartikel (refereegranskat)abstract
- The structural phases and optoelectronic properties of coevaporated CsPbI 3 thin films with a wide range of [CsI]/[PbI 2 ] compositional ratios are investigated using high throughput experimentation and gradient samples. It is found that for CsI-rich growth conditions, CsPbI 3 can be synthesized directly at low temperature into the distorted perovskite γ-CsPbI 3 phase without detectable secondary phases. In contrast, PbI 2 -rich growth conditions are found to lead to the non-perovskite δ-phase. Photoluminescence spectroscopy and optical-pump THz-probe mapping show carrier lifetimes larger than 75 ns and charge carrier (sum) mobilities larger than 60 cm 2 V −1 s −1 for the γ-phase, indicating their suitability for high efficiency solar cells. The dependence of the carrier mobilities and luminescence peak energy on the Cs-content in the films indicates the presence of Schottky defect pairs, which may cause the stabilization of the γ-phase. Building on these results, p–i–n type solar cells with a maximum efficiency exceeding 12% and high shelf stability of more than 1200 h are demonstrated, which in the future could still be significantly improved, judging on their bulk optoelectronic properties.
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| 2. |
- Chakraborty, Debasish, et al.
(författare)
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Reversible Atomization and Nano-Clustering of Pt as a Strategy for Designing Ultra-Low-Metal-Loading Catalysts
- 2022
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 126:38, s. 16194-16203
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Tidskriftsartikel (refereegranskat)abstract
- Noble metal-based catalysts have numerous industrial uses, and maximum utilization of the precious metals by lowering the metal loading is of significant interest in heterogeneous catalysis research. However, lowering the metal loading could lead to single-atom metal species formation, which may not be active for important reactions like propylene oxidation. We report a way to drastically reduce precious metal loading of catalysts by judiciously choosing an active metal/support pair and using the reversible atomization-nanoparticulate formation of transition metal on a high-surface area support. Here, Pt and MgAl2O4 are used as the transition metal and high-surface area support, respectively. Through catalytic testing and characterization using scanning transmission electron microscopy and synchrotron X-ray absorption spectroscopy, a reversible change between atomization and nano-cluster formation under oxidizing and reducing conditions has been found. Via density functional theory, favorable sites for reversible Pt adsorption are identified, including ionic Pt4+ sites that can serve to nucleate nanoclusters. Catalytic reaction modeling also rationalizes the catalytic inertness of atomic Pt sites. Finally, a re-activation mechanism for the atomized Pt based on gases present during reaction has been formulated and demonstrated.
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| 3. |
- Jeppesen, Henrik S., et al.
(författare)
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LiquidReactionCell - a versatile setup for in situ synchrotron studies of compounds in liquid suspension and solution
- 2022
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 25:5, s. 751-760
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Tidskriftsartikel (refereegranskat)abstract
- There is an increasing interest in understanding the atomic level formation of functional materials, e.g. through nucleation and growth from their precursors in solution or through chemically induced phase transitions. Such information is achievable though synchrotron-based in situ X-ray absorption spectroscopy (XAS) and total scattering (TS) experiments. In this study we present a new and versatile setup for in situ investigations of chemical reactions. Our setup, LiquidReactionCell (LRC), is constructed in borosilicate glass, i.e., it is chemically inert and transparent to visible light, and it resembles regular laboratory glassware. The setup is designed to handle homogenous solutions and fine powder suspensions at ambient conditions, and it can be used to follow chemically or light induced reactions, for example. Chemical precursors can be added during data collection, and inert conditions can be obtained in the cell. Herein, we demonstrate the versatility and use of the LRC in XAS and TS experiments. Specifically, we compare data collected on powder suspensions in the LRC with data measured on powders under ideal conditions. Bi24O31X10 (X = Cl, Br) are emerging materials for photocatalysis and are used as model compounds herein. Gratifyingly, only minor differences are observed between data collected on suspensions in the LRC and data collected on a pressed pellet (for XAS) or on a powder in a Kapton capillary (for TS). These results propose that the LRC has the potential to cover a broad range of chemical reactions.
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| 4. |
- Just, Justus, et al.
(författare)
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Insights into Nucleation and Growth of Colloidal Quaternary Nanocrystals by Multimodal X-ray Analysis
- 2021
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 15:4, s. 6439-6447
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Tidskriftsartikel (refereegranskat)abstract
- Copper chalcogenide nanocrystals find applications in photovoltaic inks, bio labels, and thermoelectric materials. We reveal insights in the nucleation and growth during synthesis of anisotropic Cu2ZnSnS4 nanocrystals by simultaneously performing in situ X-ray absorption spectroscopy (XAS) and small-angle X-ray scattering (SAXS). Real-time XAFS reveals that upon thiol injection into the reaction flask, a key copper thiolate intermediate species is formed within fractions of seconds, which decomposes further within a narrow temperature and time window to form copper sulfide nanocrystals. These nanocrystals convert into Cu2ZnSnS4 nanorods by sequentially incorporating Sn and Zn. Real-time SAXS and ex situ TEM of aliquots corroborate these findings. Our work demonstrates how combined in situ X-ray absorption and small-angle X-ray scattering enables the understanding of mechanistic pathways in colloidal nanocrystal formation.
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| 5. |
- Li, Jinzhao, et al.
(författare)
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20.8% Slot-Die Coated MAPbI3 Perovskite Solar Cells by Optimal DMSO-Content and Age of 2-ME Based Precursor Inks
- 2021
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 11:10
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Tidskriftsartikel (refereegranskat)abstract
- Solar cells incorporating metal-halide perovskite (MHP) semiconductors are continuing to break efficiency records for solution-processed solar cell devices. Scaling MHP-based devices to larger area prototypes requires the development and optimization of scalable process technology and ink formulations that enable reproducible coating results. It is demonstrated that the power conversion efficiency (PCE) of small-area methylammonium lead iodide (MAPbI3) devices, slot-die coated from a 2-methoxy-ethanol (2-ME) based ink with dimethyl-sulfoxide (DMSO) used as an additive depends on the amount of DMSO and age of the ink formulation. When adding 12 mol% of DMSO, small-area devices of high performance (20.8%) are achieved. The effect of DMSO content and age on the thin film morphology and device performance through in situ X-ray diffraction and small-angle X-ray scattering experiments is rationalized. Adding a limited amount of DMSO prevents the formation of a crystalline intermediate phase related to MAPbI3 and 2-ME (MAPbI3-2-ME) and induces the formation of the MAPbI3 perovskite phase. Higher DMSO content leads to the precipitation of the (DMSO)2MA2Pb3I8 intermediate phase that negatively affects the thin-film morphology. These results demonstrate that rational insights into the ink composition and process control are critical to enable reproducible large-scale manufacturing of MHP-based devices for commercial applications.
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| 6. |
- Lützenkirchen-Hecht, Dirk, et al.
(författare)
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Time-Resolved Grazing Incidence X-Ray Absorption Spectroscopy for the In Situ Investigation of the Initial Stages of Sputter-Deposited Copper Thin Films
- 2022
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Ingår i: Physica Status Solidi (A) Applications and Materials Science. - : Wiley. - 1862-6300. ; 219:9
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Tidskriftsartikel (refereegranskat)abstract
- The sputter deposition and the growth of thin copper films on float glass substrates are in situ studied using grazing incidence, reflection mode X-ray absorption fine structure spectroscopy with subsecond time resolution. The experimental data are compared with model calculations, assuming the presence of crystalline, face-centered cubic metallic Cu nanostructures. From a detailed analysis of the measured spectra, the film thickness as well as the surface roughness is determined, leading to a detailed understanding of the films growth as a function of the sputter deposition time. In particular, different stages of film growth can clearly be distinguished from the fits of the experimental data. The results suggest the formation of isolated, approximately nm-sized copper clusters in the initial phase of the film deposition for the first few seconds, a coalescence phase with a nominal thickness of ≈1.5−2.8 nm, constant roughness of about 1.4 nm for the subsequent ≈5 s, and finally 3D growth of the Cu crystallites in the film for later stages of film growth. Further prospects of the methodology are given.
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| 7. |
- Persson, Ingmar, et al.
(författare)
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EXAFS Study on the Coordination Chemistry of the Solvated Copper(II) Ion in a Series of Oxygen Donor Solvents
- 2020
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 59:14
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Tidskriftsartikel (refereegranskat)abstract
- The structures of the solvated copper(II) ion in water and nine organic oxygen donor solvents with similar electron-pair donor ability, but with different space-demanding properties at coordination, have been studied by EXAFS. N,N′-Dimethylpropyleneurea and N,N,N′,N′-tetramethylurea are sufficiently space demanding at coordination to make the axial positions not accessible, resulting in square-planar copper(II) solvate complexes with an intense green color. The mean Cu-O bond distances in these two solvate complexes are 1.939(3) and 1.935(3) Å, respectively. The best fits of the remaining solvates, which are light blue in different hues, are obtained with a Jahn-Teller distorted-octahedral model consisting of four strongly bound solvent molecules in the equatorial positions at 1.96(2) Å and two in the axial positions but with different Cu-Oax bond distances: ca. 2.15 and 2.32 Å. This is in agreement with observations in solid-state structures of compounds containing hexaaquacopper(II) complexes crystallizing in noncentrosymmetric space groups and all reported crystal structures containing a [Cu(H2O)5(O-ligand)] complex with Jahn-Teller distortion. Such a structure is in agreement with previous EPR and EXAFS studies proving the hydrated copper(II) ion to be a noncentrosymmetric complex in aqueous solution. The refinements of the EXAFS data of the solids [Cu(H2O)6](ClO4)2, [Cu(H2O)6](BrO3)2, [Cu(H2O)6]SiF6, Cu(NO3)2·2.5H2O, and CuSO4·5H2O gave Cu-O bond distances significantly different from those reported in the crystallographic studies but similar to the configuration and bond distances in the hydrated copper(II) ion in aqueous solution. This may depend on whether the orientation of the axial positions is random in one or three dimensions, giving a mean structure of the solid with symmetry higher than that of the individual complexes. This study presents the very first experimental data from the new X-ray absorption spectroscopy beamline Balder at the MAX IV synchrotron radiation facility in Lund, Sweden, as well as the utilized properties of the beamline.
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| 8. |
- Suchan, Klara, et al.
(författare)
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Multi-Stage Phase-Segregation of Mixed Halide Perovskites under Illumination : A Quantitative Comparison of Experimental Observations and Thermodynamic Models
- 2023
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 33:3
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Tidskriftsartikel (refereegranskat)abstract
- Photo- and charge-carrier-induced ion migration is a major challenge when utilizing metal halide perovskite semiconductors for optoelectronic applications. For mixed iodide/bromide perovskites, the compositional instability due to light- or electrical bias induced phase-segregation restricts the exploitation of the entire bandgap range. Previous experimental and theoretical work suggests that excited states or charge carriers trigger the process, but the exact mechanism is still under debate. To identify the mechanism and cause of light-induced phase-segregation phenomena, the full compositional range of methylammonium lead bromide/iodide samples are investigated, MAPb(BrxI1-x)3 with x = 0…1, by simultaneous in situ X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy during illumination. The quantitative comparison of composition-dependent in situ XRD and PL shows that at excitation densities of 1 sun, only the initial stage of photo-segregation is rationalized with the previously established thermodynamic models. However, a progression of the phase segregation is observed that is rationalized by considering long-lived accumulative photo-induced material alterations. It is suggested that (additional) photo-induced defects, possibly halide vacancies and interstitials, need to be considered to fully rationalize light-induced phase segregation and anticipate the findings to provide crucial insight for the development of more sophisticated models.
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| 9. |
- Suchan, Klara, et al.
(författare)
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Optical : In situ monitoring during the synthesis of halide perovskite solar cells reveals formation kinetics and evolution of optoelectronic properties
- 2020
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 8:20, s. 10439-10449
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Tidskriftsartikel (refereegranskat)abstract
- The formation mechanism and the evolution of optoelectronic properties during annealing of chlorine-derived methylammonium lead iodide (MAPbI3-xClx) are investigated in detail combining in situ and ex situ optical and structural characterization. Using in situ optical reflectometry we are able to monitor the evolution of the MAPbI3-xClx phase as a function of time and processing temperature. The formation kinetics is fitted using an improved Johnson-Mehl-Avrami-Kolmogorov model and a delayed formation of MAPbI3-xClx is found when chlorine is present in the precursor. This is verified by X-ray diffraction and X-ray fluorescence measurements. From absolute photoluminescence measurements we determine the implied Voc during film formation, which exhibits a maximum at a specific time during the annealing process. In conjunction with ex situ time-resolved photoluminescence we deduce a decrease in the net doping density for increased annealing times, while the minority carrier lifetime stays constant. We thus demonstrate the potential of in situ optical spectroscopy to monitor and tailor the electronic properties of hybrid perovskites directly during film growth, which can be easily applied to different growth recipes and synthesis environments.
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| 10. |
- van Duren, Stephan, et al.
(författare)
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In Situ Monitoring of Cu2ZnSnS4 Absorber Formation With Raman Spectroscopy During Mo/Cu2SnS3/ZnS Thin-Film Stack Annealing
- 2017
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Ingår i: IEEE Journal of Photovoltaics. - : IEEE. - 2156-3381 .- 2156-3403. ; 7:3, s. 906-912
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, Cu-2 ZnSn(S,Se)(4) (kesterite) has become increasingly popular as a sustainable alternative absorber material. Many processes for kesterite synthesis involve a high temperature annealing step (>450 degrees C). This study investigates the possibility of Raman spectroscopy as an in situ monitoring technique during high temperature annealing up to 550 degrees C. Temperature-dependent behavior of Cu2SnS3 (CTS) and Cu2ZnSnS4 (CZTS) was studied for reference purposes. The synthesis of CZTS was performed by annealing a stacked Mo/CTS/ZnS precursor on a glass substrate. Annealing of the precursor stack resulted in formation of kesterite and could be monitored in situ by its main A-mode at 338 cm(-1). At higher temperatures, this mode shifts to lower wavenumbers, is broadened and reduced in intensity. This can be attributed to combined effects of thermal expansion and anharmonic phonon coupling. The shift of the peak position is linearly proportional to the temperature. Thus, given proper calibration, fitting the peak position of the 338 cm(-1) mode during the process yields the sample temperature. Implementation of in situ monitoring with Raman spectroscopy would be a step forward toward desired process control and monitoring during this crucial high temperature annealing step in kesterite synthesis.
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| 11. |
- van Duren, Stephan, et al.
(författare)
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Raman spectroscopy study on in-situ monitoring of Cu2ZnSnS4 synthesis
- 2015
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Ingår i: 2015 IEEE 42ND PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC). - : IEEE conference proceedings. - 9781479979448
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Konferensbidrag (refereegranskat)abstract
- This study investigates the possibility of Raman spectroscopy as an in-situ monitoring tool for the synthesis of the solar cell material Cu2ZnSnS4 (CZTS) by annealing a stacked precursor ZnS/Cu2SnS3 on a Mo-coated glass substrate. Temperature dependent behaviour of Raman scattering for ZnS and Cu2SnS3 is studied. Both phases can still be detected at respectively 450 degrees C and 550 degrees C. Annealing of Mo/CTS/ZnS precursor stacks resulted in in-situ observation of kesterite CZTS formation with Raman spectroscopy. This is a step towards in-situ optical process control desired in kesterite fabrication.
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| 12. |
- Zhang, Longhai, et al.
(författare)
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Rational Design of Multinary Metal Chalcogenide Bi0.4Sb1.6Te3 Nanocrystals for Efficient Potassium Storage
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Ingår i: Advanced Materials. - 0935-9648.
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Tidskriftsartikel (refereegranskat)abstract
- Multinary metal chalcogenides hold considerable promise for high-energy potassium storage due to their numerous redox reactions. However, challenges arise from issues such as volume expansion and sluggish kinetics. Here, a design featuring a layered ternary Bi0.4Sb1.6Te3 anchored on graphene layers as a composite anode, where Bi atoms act as a lattice softening agent on Sb, is presented. Benefiting from the lattice arrangement in Bi0.4Sb1.6Te3 and structure, Bi0.4Sb1.6Te3/graphene exhibits a mitigated expansion of 28% during the potassiation/depotassiation process and demonstrates facile K+ ion transfer kinetics, enabling long-term durability of 500 cycles at various high rates. Operando synchrotron diffraction patterns and spectroscopies including in situ Raman, ex situ adsorption, and X-ray photoelectron reveal multiple conversion and alloying/dealloying reactions for potassium storage at the atomic level. In addition, both theoretical calculations and electrochemical examinations elucidate the K+ migration pathways and indicate a reduction in energy barriers within Bi0.4Sb1.6Te3/graphene, thereby suggesting enhanced diffusion kinetics for K+. These findings provide insight in the design of durable high-energy multinary tellurides for potassium storage.
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