| 1. |
- Freys, Jonathan C., et al.
(författare)
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Ru-based donor-acceptor photosensitizer that retards charge recombination in a p-type dye-sensitized solar cell
- 2012
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41:42, s. 13105-13111
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Tidskriftsartikel (refereegranskat)abstract
- We report on the synthesis and characterization of a donor-acceptor ruthenium polypyridyl complex as a photosensitizer for p-type dye-sensitized solar cells (DSSCs). The electrochemical, photophysical, and photovoltaic performance of two ruthenium-based photosensitizers were tested in NiO-based DSSCs; bis-(2,2′-bipyridine-4,4′-dicarboxylic acid) 2N-(1,10-phenanthroline)-4-nitronaphthalene-1,8-dicarboximide ruthenium(ii), ([Ru(dcb) 2(NMI-phen)](PF 6) 2) and tris-(2,2′-bipyridine-4,4′-dicarboxylic acid) 3 ruthenium(ii), [(Ru(dcb) 3)Cl 2]. The presence of an electron-accepting group, 4-nitronaphthalene-1,8-dicarboximide (NMI), attached to the phenanthroline of [Ru(dcb) 2(NMI-phen)] 2+ resulted in long-lived charge separation between reduced [Ru(dcb) 2(NMI-phen)] 2+ and NiO valence band holes; 10-50 μs. In the reduced state for [Ru(dcb) 2(NMI-phen)] 2+, the electron localized on the distal NMI group. In tests with I 3 -/I - and Co(4,4′-di-tert-butyl-bipyridine) 3 2+/3+ electrolytes, [Ru(dcb) 2(NMI-phen)] 2+ outperformed [Ru(dcb) 3] 2+ in solar cell efficiency in devices. A record APCE (25%) was achieved for a ruthenium photosensitizer in a p-type DSSC. Insights on photosensitizer regeneration kinetics are included.
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| 2. |
- Gardner, James M., 1982-, et al.
(författare)
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Evidence for Iodine Atoms as Intermediates in the Dye Sensitized Formation of I-ˆ’I Bonds
- 2008
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 130:51, s. 17252-17253
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Tidskriftsartikel (refereegranskat)abstract
- Visible light excitation of [Ru(bpz)2(deeb)](PF6)2, where bpz is 2,2?-bipyrazine and deeb is 4,4?-(CO2Et)2-2,2?-bipyridine, in acetonitrile solutions with iodide is shown to initiate excited-state electron transfer reactions that yield iodine atoms. The iodine atoms subsequently react with iodide to form the I?I bond in I2??. The resultant Ru(bpz?)(bpz)(deeb)+, I2?? stores ?1.64 eV of free energy and returns cleanly to ground-state products with kcr = (2.1 ± 0.3) ? 1010 M?1 s?1.
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| 3. |
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| 4. |
- Cappel, Ute B., et al.
(författare)
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Electronic Structure Characterization of Cross-Linked Sulfur Polymers
- 2018
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Ingår i: ChemPhysChem. - : WILEY-V C H VERLAG GMBH. - 1439-4235 .- 1439-7641. ; 19:9, s. 1041-1047
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- Church, Tamara L., et al.
(författare)
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A microporous polymer based on nonconjugated hindered biphenyls that emits blue light
- 2024
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Microporous organic polymers that have three-dimensional connectivity stemming from monomers with tetrahedral or tetrahedron-like geometry can have high surface areas and strong fluorescence. There are however few examples of such polymers based on hindered biaryls, and their fluorescence has not been studied. Hypothesizing that the contortion in a hindered biphenyl moiety would modulate the optical properties of a polymer built from it, we synthesized a meta-enchained polyphenylene from a 2,2ʹ,6,6ʹ-tetramethylbiphenyl-based monomer, in which the two phenyl rings are nearly mutually perpendicular. The polymer was microporous with SBET = 495 m2 g−1. The polymer absorbed near-UV light and emitted blue fluorescence despite the meta-enchainment that would have been expected to break the conjugation. A related copolymer, synthesized from 2,2ʹ,6,6ʹ-tetramethylbiphenyl-based and unsubstituted biphenyl-based monomers, was microporous but not fluorescent. © The Author(s) 2024.
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| 6. |
- Farnum, Byron H., et al.
(författare)
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Flash-Quench Technique Employed To Study the One-Electron Reduction of Triiodide in Acetonitrile : Evidence for a Diiodide Reaction Product
- 2010
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 49:22, s. 10223-10225
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Tidskriftsartikel (refereegranskat)abstract
- The one-electron reduction of triiodide (I3?) by a reduced ruthenium polypyridyl compound was studied in an acetonitrile solution with the flash-quench technique. Reductive quenching of the metal-to-ligand charge-transfer excited state of [RuII(deeb)3]2+ by iodide generated the reduced ruthenium compound [RuII(deeb?)(deeb)2]+ and diiodide (I2??). The subsequent reaction of [RuII(deeb?)(deeb)2]+ with I3? indicated that I2?? was a product that appeared with a second-order rate constant of (5.1 ± 0.2) ? 109 M?1 s?1. After correction for diffusion and some assumptions, Marcus theory predicted a formal potential of ?0.58 V (vs SCE) for the one-electron reduction of I3?. The relevance of this reaction to solar energy conversion is discussed.
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| 7. |
- Franchi, Daniele, et al.
(författare)
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Effect of the Ancillary Ligand on the Performance of Heteroleptic Cu(I) Diimine Complexes as Dyes in Dye-Sensitized Solar Cells
- 2022
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 5:2, s. 1460-1470
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Tidskriftsartikel (refereegranskat)abstract
- A series of heteroleptic Cu(I) diimine complexes with different ancillary ligands and 6,6'-dimethyl-2,2'-bipyridine-4,4'-dibenzoic acid (dbda) as the anchoring ligand were selfassembled on TiO2 surfaces and used as dyes for dye-sensitized solar cells (DSSCs). The binding to the TiO2 surface was studied by hard X-ray photoelectron spectroscopy for a brominecontaining complex, confirming the complex formation. The performance of all complexes was assessed and rationalized on the basis of their respective ancillary ligand. The DSSC photocurrent-voltage characteristics, incident photon-to-current conversion efficiency (IPCE) spectra, and calculated lowest unoccupied molecular orbital (LUMO) distributions collectively show a push-pull structural dye design, in which the ancillary ligand exhibits an electron-donating effect that can lead to improved solar cell performance. By analyzing the optical properties of the dyes and their solar cell performance, we can conclude that the presence of ancillary ligands with bulky substituents protects the Cu(I) metal center from solvent coordination constituting a critical factor in the design of efficient Cu(I)-based dyes. Moreover, we have identified some components in the I-/I-3(-)-based electrolyte that causes dissociation of the ancillary ligand, i.e., TiO2 photoelectrode bleaching. Finally, the detailed studies on one of the dyes revealed an electrolyte-dye interaction, leading to a dramatic change of the dye properties when adsorbed on the TiO2 surface.
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| 8. |
- Gao, Jiajia, et al.
(författare)
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Electrochemical impedance and X-ray absorption spectroscopy analyses of degradation in dye-sensitized solar cells containing cobalt tris(bipyridine) redox shuttles
- 2022
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 24:31, s. 18888-18895
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical impedance spectroscopy (EIS) is a commonly used steady-state technique to examine the internal resistance of electron-transfer processes in solar cell devices, and the results are directly related to the photovoltaic performance. In this study, EIS was performed to study the effects of accelerated ageing, aiming for insights into the degradation mechanisms of dye-sensitized solar cells (DSSCs) containing cobalt tris(bipyridine) complexes as redox mediators. Control experiments based on aged electrolytes differing in concentrations of the redox couple components and cation co-additives were conducted to reveal the correlation of the cell degradation with external and internal properties. The failure modes of the cells emerged as changes in the kinetics of charge- and ion-transfer processes. An insufficient concentration of the redox complexes, in particular Co(iii), was found to be the main reason for the inferior performance after ageing. The related characterization of electrolytes aged outside the solar cell devices confirms the loss of active Co(iii) complexes in the device electrolytes. A new EIS feature at low frequencies emerged during ageing and was analysed. The new EIS feature demonstrates the presence of an unexpected rate-limiting, charge-transfer process in aged devices, which can be attributed to the TiO2/electrolyte interface. High-resolution fluorescence detected X-ray absorption spectroscopy (HERFD-XAS) was performed to identify the reduction of a part of Co(iii) to Co(II) after ageing, by investigating the Co K absorption edge. The HERFD-XAS data suggested a partial reduction of Co(iii) to Co(ii), accompanied by a difference in symmetry of the reduced species.
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| 9. |
- Gao, Jiajia, et al.
(författare)
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Light-Induced Interfacial Dynamics Dramatically Improve the Photocurrent in Dye-Sensitized Solar Cells : An Electrolyte Effect
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 10:31, s. 26241-26247
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Tidskriftsartikel (refereegranskat)abstract
- A significant increase in the photocurrent generation during light soaking for solar cells sensitized by the triphenylamine-based D-pi-A organic dyes (PD2 and LEG1) and mediated by cobalt bipyridine redox complexes has been observed and investigated. The crucial role of the electrolyte has been identified in the performance improvement. Control experiments based on a pretreatment strategy reveals TBP as the origin. The increase in the current and IPCE has been interpreted by the interfacial charge-transfer kinetics studies. A slow component in the injection kinetics was exposed for this system. This change explains the increase in the electron lifetime and collection efficiency. Photoelectron spectroscopic measurements show energy shifts at the dye/TiO2 interface, leading us to formulate a hypothesis with respect to an electrolyte induced dye reorganization at the surface.
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| 10. |
- Gardner, James M., 1982-, et al.
(författare)
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Electrodeposition of Nanometer-Sized Ferric Oxide Materials in Colloidal Templates for Conversion of Light to Chemical Energy
- 2011
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Ingår i: Journal of Nanomaterials. - : Hindawi Publishing Corporation. - 1687-4110 .- 1687-4129. ; 2011, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- Colloidal crystal templates were prepared by gravitational sedimentation of 0.5 micron polystyrene particles onto fluorine-doped tin oxide (FTO) electrodes. Scanning electron microscopy (SEM) shows that the particles were close packed and examination of successive layers indicated a predominantly face-centered-cubic (fcc) crystal structure where the direction normal to the substrate surface corresponds to the (111) direction. Oxidation of aqueous ferrous solutions resulted in the electrodeposition of ferric oxide into the templates. Removal of the colloidal templates yielded ordered macroporous electrodes (OMEs) that were the inverse structure of the colloidal templates. Current integration during electrodeposition and cross-sectional SEM images revealed that the OMEs were about 2 mu m thick. Comparative X-ray diffraction and infrared studies of the OMEs did not match a known phase of ferric oxide but suggested a mixture of goethite and hematite. The spectroscopic properties of the OMEs were insensitive to heat treatments at 300. C. The OMEs were utilized for photoassisted electrochemical oxidation. A sustained photocurrent was observed from visible light in aqueous photoelectrochemical cells. Analysis of photocurrent action spectra revealed an indirect band gap of 1.85 eV. Addition of formate to the aqueous electrolytes resulted in an approximate doubling of the photocurrent.
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| 11. |
- Gardner, James M, 1982-, et al.
(författare)
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Light-Driven Electron Transfer between a Photosensitizer and a Proton-Reducing Catalyst Co-adsorbed to NiO
- 2012
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 134:47, s. 19322-19325
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Tidskriftsartikel (refereegranskat)abstract
- While intermolecular hole-hopping along the surface of semiconductors is known, there are no previous examples of electron-hopping between molecules on a surface. Herein, we present the first evidence of electron transfer from the photoreduced sensitizer Coumarin-343 (C343) to complex 1, both bound on the surface of NiO. In solution, 1 has been shown to be a mononuclear Fe-based proton-reducing catalyst. The reduction of 1 is reversible and occurs within 50 ns after excitation of C343. Interfacial recombination between the reduced 1(-) and NiO hole occurs on a 100 µs time scale by non-exponential kinetics. The observed process is the first essential step in the photosensitized generation of H2 from a molecular catalyst in the absence of a sacrificial donor reagent.
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| 12. |
- Gardner, James M., 1982-, et al.
(författare)
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Visible Light Generation of Iodine Atoms and I-ˆ’I Bonds : Sensitized I-ˆ’ Oxidation and I3-ˆ’ Photodissociation
- 2009
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 131:44, s. 16206-16214
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Tidskriftsartikel (refereegranskat)abstract
- Direct 355 or 532 nm light excitation of TBAI3, where TBA is tetrabutyl ammonium, in CH3CN at room temperature yields an iodine atom, I?, and an iodine radical anion, I2??. In the presence of excess iodide, the iodine atom reacts quantitatively to yield a second equivalent of I2?? with a rate constant of k = 2.5 ± 0.4 ? 1010 M?1 s?1. The I2?? intermediates are unstable with respect to disproportionation and yield initial reactants, k = 3.3 ± 0.1 ? 109 M?1 s?1. The coordination compound Ru(bpz)2(deeb)(PF6)2, where bpz is 2,2?-bipyrazine and deeb is 4,4?-(C2H5CO2)2-2,2?-bipyridine, was prepared and characterized for mechanistic studies of iodide photo-oxidation in acetonitrile at room temperature. Ru(bpz)2(deeb)2+ displayed a broad metal-to-ligand charge transfer (MLCT) absorption band at 450 nm with ε = 1.7 ? 104 M?1 cm?1. Visible light excitation resulted in photoluminescence with a corrected maximum at 620 nm, a quantum yield ? = 0.14, and an excited state lifetime τ = 1.75 ?s from which kr = 8.36 ? 104 s?1 and knr = 5.01 ? 105 s?1 were abstracted. Arrhenius analysis of the temperature dependent excited state lifetime revealed an activation energy of ?2500 cm?1 and a pre-exponential factor of 1010 s?1, assigned to activated surface crossing to a ligand field or MLCT excited state. Steady state light excitation of Ru(bpz)2(deeb)2+ in a 20 mM TBAI acetonitrile solution resulted in ligand loss photochemistry with a quantum yield of 5 ? 10?5. The MLCT excited state was dynamically quenched by iodide with Ksv = 1.1 ? 105 M?1 and kq = 6.6 ± 0.3 ? 1010 M?1 s?1, a value consistent with diffusion-limited electron transfer. Excited state hole transfer to iodide was quantitative but the product yield was low due to poor cage escape yields, ?CE = 0.042 ± 0.001. Nanosecond transient absorption was used to quantify the appearance of two photoproducts [Ru(bpz?)(bpz)(deeb)]+ and I2??. The coincidence of the rate constants for [Ru(bpz?)(bpz)(deeb)]+ formation and for excited state decay indicated reductive quenching by iodide. The rate constant for the appearance of I2?? was about a factor of 3 slower than excited state decay, k = 2.4 ± 0.2 ? 1010 M?1 s?1, indicating that I2?? was not a primary photoproduct of excited state electron transfer. A mechanism was proposed where an iodine atom was the primary photoproduct that subsequently reacted with iodide, I? + I? ? I2??. Charge recombination Ru(bpz?)(bpz)(deeb)+ + I2?? ? Ru(bpz)2(deeb)2+ + 2I? was highly favored, ?Go = ?1.64 eV, and well described by a second-order equal concentration kinetic model, kcr = 2.1 ± 0.3 ? 1010 M?1 s?1.
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| 13. |
- Haydous, Fatima, et al.
(författare)
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The impact of ligands on the synthesis and application of metal halide perovskite nanocrystals
- 2021
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 9:41, s. 23419-23443
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Tidskriftsartikel (refereegranskat)abstract
- Metal halide perovskites have emerged as attractive materials for use in solar cells, light emitting diodes and other optoelectronic devices, mainly due to their impressive charge transport properties, strong light absorption, long carrier diffusion lengths and long excited state lifetime. The extensive research on these materials has paved the way for a new class of materials: metal halide perovskite nanocrystals (NCs). Due to their high photoluminescence quantum yield and narrow emission that can be tuned by size and compositional variations, perovskite NCs are considered to be ideal candidates compared to traditional quantum dots. With the growing interest in these materials and the current challenges in their commercialization, this review aims mainly to provide the necessary understanding of the influence of capping ligands on the synthesis and application of perovskite NCs. The different synthetic approaches and the role of ligands in determining the morphological and optical properties of the resulting NCs will be discussed. Thereafter, we review the advances in understanding the surface chemistry and ligation in the metal halide perovskite NCs. Lastly, we review the ligand exchange and management processes that are shown to be beneficial in improving the performance and stability of perovskite nanocrystal films for optoelectronic applications.
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| 14. |
- Jamshidi, Mahboubeh, et al.
(författare)
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Copper(I) Iodide Thin Films: Deposition Methods and Hole-Transporting Performance
- 2024
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Ingår i: Molecules. - : Multidisciplinary Digital Publishing Institute (MDPI). - 1431-5157 .- 1420-3049. ; 29:8
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Forskningsöversikt (refereegranskat)abstract
- The pursuit of p-type semiconductors has garnered considerable attention in academia and industry. Among the potential candidates, copper iodide (CuI) stands out as a highly promising p-type material due to its conductivity, cost-effectiveness, and low environmental impact. CuI can be employed to create thin films with >80% transparency within the visible range (400–750 nm) and utilizing various low-temperature, scalable deposition techniques. This review summarizes the deposition techniques for CuI as a hole-transport material and their performance in perovskite solar cells, thin-film transistors, and light-emitting diodes using diverse processing methods. The preparation methods of making thin films are divided into two categories: wet and neat methods. The advancements in CuI as a hole-transporting material and interface engineering techniques hold promising implications for the continued development of such devices.
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| 15. |
- Jamshidi, Mahboubeh, et al.
(författare)
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Photoluminescent copper(I) iodide alkylpyridine thin films as sensors for volatile halogenated compounds
- 2023
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Ingår i: Frontiers in Chemistry. - : Frontiers Media SA. - 2296-2646. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents the fabrication and characterization of [CuI(L)]n thin films, where L represents various alkylpyridine ligands including 4-methylpyridine, 3-methylpyridine, 2-methylpyridine, 4-tbutylpyridine, 3,4-dimethylpyridine, and 3,5-dimethylpyridine. The thin films were synthesized by exposing the corresponding ligands to CuI thin films through vapor deposition. The coordination reactions occurring on the films were investigated using PXRD and time-dependent photoluminescence spectroscopy, and a comparison was made between the structures of the thin films and the corresponding powder phases. The films showed primarly blue emission (λem = 457–515 nm) and polymeric structures with excited state lifetimes ranging from 0.6 to 5.5 μs. Significantly, the studied compounds exhibited fast reversible luminescence quenching when exposed to vapors of dichloromethane and dibromomethane (15 and 30 min respectively), and the luminescence was restored upon re-exposure to the alkylpyridine ligand (after 20 min). These findings indicate that these thin films hold promise for applications as sensors (with sensitive and reversible detection capability) for volatile halogen-based compounds (VHC).
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| 16. |
- Karlsson, Mattias E., et al.
(författare)
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Synthesis of Zinc Oxide Nanorods via the Formation of Sea Urchin Structures and Their Photoluminescence after Heat Treatment
- 2018
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Ingår i: Langmuir. - : AMER CHEMICAL SOC. - 0743-7463 .- 1520-5827. ; 34:17, s. 5079-5087
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Tidskriftsartikel (refereegranskat)abstract
- A protocol for the aqueous synthesis of ca. 1-mu m-long zinc oxide (ZnO) nanorods and their growth at intermediate reaction progression is presented, together with photoluminescence (PL) characteristics after heat treatment at temperatures of up to 1000 degrees C. The existence of solitary rods after the complete reaction (60 min) was traced back to the development of sea urchin structures during the first 5 s of the precipitation. The rods primarily formed in later stages during the reaction due to fracture, which was supported by the frequently observed broken rod ends with sharp edges in the final material, in addition to tapered uniform rod ends consistent with their natural growth direction. The more dominant rod growth in the c direction (extending the length of the rods), together with the appearance of faceted surfaces on the sides of the rods, occurred at longer reaction times (>5 min) and generated zinc-terminated particles that were more resistant to alkaline dissolution. A heat treatment for 1 h at 600 or 800 degrees C resulted in a smoothing of the rod surfaces, and PL measurements displayed a decreased defect emission at ca. 600 nm, which was related to the disappearance of lattice imperfections formed during the synthesis. A heat treatment at 1000 degrees C resulted in significant crystal growth reflected as an increase in luminescence at shorter wavelengths (ca. 510 nm). Electron microscopy revealed that the faceted rod structure was lost for ZnO rods exposed to temperatures above 600 degrees C, whereas even higher temperatures resulted in particle sintering and/or mass redistribution along the initially long and slender ZnO rods. The synthesized ZnO rods were a more stable Wurtzite crystal structure than previously reported ball-shaped ZnO consisting of merging sheets, which was supported by the shifts in PL spectra occurring at ca. 200 degrees C higher annealing temperature, in combination with a smaller thermogravimetric mass loss occurring upon heating the rods to 800 degrees C.
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| 17. |
- Karlsson, Mattias E., et al.
(författare)
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The effect of ZnO particle lattice termination on the DC conductivity of LDPE nanocomposites
- 2020
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Ingår i: Materials Advances. - : Royal Society of Chemistry (RSC). - 2633-5409. ; 1:6, s. 1653-1664
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Tidskriftsartikel (refereegranskat)abstract
- The effects of particle surface termination by zinc or oxygen were evaluated for composites containing micro-sized ZnO particles with rod shapes (17% oxygen terminations) or ball shapes (67% oxygen terminations), and it was found that the rods gave a conductivity (1.2 x 10(-16) S m(-1)) half that given by the ball-shaped particles (2.4 x 10(-16) S m(-1)). Both composites containing the micro-sized particles showed a conductivity almost two orders of magnitude lower than that of the LDPE reference material (1.2 x 10(-14) S m(-1)). When a 5 nm thick silica coating was applied to the particles, the silica encapsulation eliminated the difference between the particles and resulted in both cases in an increase in conductivity by an order of magnitude to ca. 2 x 10(-15) S m(-1). The conductivity was still lower than that of the pristine polyethylene polymer. It was concluded that neither the particle morphology nor the inter-particle distance (1 mu m for rods and 8 mu m for balls) had any effect on the conductivity of the composites for identically terminated particles, while demonstrating that the conductivity of these materials relies uniquely on the particle surface terminations. In contrast, a markedly reduced conductivity was observed for composites containing the same particles but terminated with aliphatic hydrocarbon tails, the conductivity for both rod-shaped and ball-shaped particles (1 x 10(-16) S m(-1)) being reduced to even lower values than for the pristine particles without surface modification. The same trend was observed with the 25 nm ZnO nanoparticles, showing a record low conductivity of 1 x 10(-17) S m(-1) for 3 wt% nanoparticles with aliphatic hydrocarbon tails. In practical applications, this would permit higher operation voltages than currently employed HVDC cable systems by controlling the resistivity of the composite insulation for various electric fields and temperatures and making it possible to tailor the dielectric design of cable components.
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| 18. |
- Kore, Bhushan P., et al.
(författare)
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Moisture tolerant solar cells by encapsulating 3D perovskite with long-chain alkylammonium cation-based 2D perovskite
- 2021
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Ingår i: Communications Materials. - : Springer Nature. - 2662-4443. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- Long-term stability is an essential requirement for perovskite solar cells to be commercially viable. Encapsulating 3D perovskites with 2D perovskite structures is an effective strategy for improving resistance to moisture. However, long-chain alkylammonium cation-based 2D perovskites have been rarely studied in solar cells. Here, we study three different alkyl chain length organic cation-based 2D perovskite coatings for 3D perovskites. The 2D perovskite incorporated solar cells show significant improvement in solar cell stability with limited compromise in solar cell efficiency, with the longest alkyl chain length sample showing only a 20% drop in power conversion efficiency after 6 months at a relative humidity of 25-80%, and could be completely immersed in water for a few minutes before degradation started. The 2D perovskite coating also mitigated non-radiative recombination in the light-absorbing 3D perovskite, leading to an enhancement in the open circuit voltage. These findings suggest that long-chain alkylammonium cation based 2D perovskites can improve the environmental stability of 3D based perovskites without significant losses to device performance. Moisture resistance is vital for commercializing perovskite solar cells. Here, long-chain alkylammonium cation-based 2D perovskites are used to coat 3D perovskite, enabling stable performance for six months with only a 20 % drop in power conversion efficiency.
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| 19. |
- Kore, Bhushan P., et al.
(författare)
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Water-resistant 2D lead(ii) iodide perovskites : correlation between optical properties and phase transitions
- 2020
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Ingår i: Materials Advances. - : Royal Society of Chemistry (RSC). - 2633-5409. ; 1:7, s. 2395-2400
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Tidskriftsartikel (refereegranskat)abstract
- The hybrid perovskite-based solar cells have achieved photovoltaic efficiencies comparable to that of the silicon-based solar cells; however, the light-absorbing perovskite materials are not stable and undergo rapid degradation in the presence of moisture. There are only a few water-stable 2D perovskite materials that have been explored so far. Keeping this in mind, we incorporated 3 different long-chain alkylammonium cations in 2D perovskites using a generic solution synthesis route where the saturated precursor solution was slowly cooled down to room temperature resulting in the single crystals of the 2D perovskites and studied their optical properties and stability against moisture. The prepared 2D perovskites demonstrated robust stability under ambient conditions as well as resistance to water. The main highlight of the present study is 2D perovskites emit bright green light in the 494-520 nm range even in the presence of water. We anticipate that our results on the water stable perovskite will not only motivate the use of these long alkyl chain cation-based 2D perovskite materials in perovskite solar cells for achieving the prolonged device stability but also for the next generation LEDs and display technologies.
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| 20. |
- Leandri, Valentina, et al.
(författare)
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Coumarin as a Quantitative Probe for Hydroxyl Radical Formation in Heterogeneous Photocatalysis
- 2019
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:11, s. 6667-6674
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we have assessed coumarin as a quantitative probe for hydroxyl radical formation in heterogeneous photocatalysis. Upon reaction with the hydroxyl radical, coumarin produces several hydroxylated products, of which one, 7-OH-coumarin, is strongly fluorescent. The fluorescence emission is strongly affected by inner filtering due to the presence of coumarin. Therefore, we performed a series of calibration experiments to correct for the coumarin concentration. From the calibration experiments, we could verify that the inner-filtering effect can be attributed to the competing absorption of the fluorescence excitation light between coumarin and 7-OH-coumarin. Through judicious calibration for the inner-filtering effects, the corrected results for the photocatalytic system show that the rate of hydroxyl scavenging is constant with time for initial coumarin concentrations of ≥50 μM under the conditions of our experiments. The rate increases linearly with coumarin concentration, as expected from the Langmuir–Hinshelwood model. Within the coumarin concentration range used here, the photocatalyst surface does not become saturated. Given the fact that the highest coumarin concentration used (1 mM) in this work is quite close to the solubility limit, we conclude that coumarin cannot be used to assess the full photocatalytic capacity of the system, i.e., surface saturation is never reached. The rate of hydroxyl radical scavenging will, to a large extent, depend on the affinity to the surface, and it is therefore not advisable to use coumarin as a probe for photocatalytic efficiency when comparing different photocatalysts.
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| 21. |
- Leandri, Valentina, et al.
(författare)
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Electronic and Structural Effects of Inner Sphere Coordination of Chloride to a Homoleptic Copper(II) Diimine Complex
- 2018
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 57:8, s. 4556-4562
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Tidskriftsartikel (refereegranskat)abstract
- The reaction of CuCl2 with 2,9-dimethyl-1,10-phenanthroline (dmp) does not lead to the formation of [Cu(dmp)(2)](Cl)(2) but instead to [Cu(dmp)(2)Cl]Cl, a 5-coordinated complex, in which one chloride is directly coordinated to the metal center. Attempts at removing the coordinated chloride by changing the counterion by metathesis were unsuccessful and resulted only in the exchange of the noncoordinated chloride, as confirmed from a crystal structure analysis. Complex [Cu-(dmp)(2)Cl]PF6 exhibits a reversible cyclic voltammogram characterized by a significant peak splitting between the reductive and oxidative waves (0.85 and 0.60 V vs NHE, respectively), with a half-wave potential E-1/2 = 0.73 V vs NHE. When reduced electrochemically, the complex does not convert into [Cu(dmp)(2)](+), as one may expect. Instead, [Cu(dmp)(2)](+) is isolated as a product when the reduction of [Cu(dmp)(2)Cl]PF6 is performed with L-ascorbic acid, as confirmed by electrochemistry, NMR spectroscopy, and diffractometry. [Cu(dmp)(2)](2+) complexes can be synthesized starting from Cu(II) salts with weakly and noncoordinating counterions, such as perchlorate. Growth of [Cu(dmp)(2)](ClO4)(2) crystals in acetonitrile results in a 5-coordinated complex, [Cu(dmp)(2)(CH3CN)](ClO4)(2), in which a solvent molecule is coordinated to the metal center. However, solvent coordination is associated with a dynamic decoordination-coordination behavior upon reduction and oxidation. Hence, the cyclic voltammogram of [Cu(dmp)(2)(CH3CN)](2+) is identical to the one of [Cu(dmp)(2)](+), if the measurements are performed in acetonitrile. The current results show that halide ions in precursors to Cu(II) metal-organic coordination compound synthesis, and most likely also other multivalent coordination centers, are not readily exchanged when exposed to presumed strongly binding and chelating ligand, and thus special care needs to be taken with respect to product characterization.
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| 22. |
- Leandri, Valentina, et al.
(författare)
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Excited-State Dynamics of [Ru(bpy)(3)](2+) Thin Films on Sensitized TiO2 and ZrO2
- 2019
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Ingår i: ChemPhysChem. - : Wiley-VCH Verlagsgesellschaft. - 1439-4235 .- 1439-7641. ; 20:4, s. 618-626
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Tidskriftsartikel (refereegranskat)abstract
- The excited state dynamics of Tris(2,2 '-bipyridine)ruthenium(II) hexafluorophosphate, [Ru(bpy)(3)(PF6)(2)], was investigated on the surface of bare and sensitized TiO2 and ZrO2 films. The organic dyes LEG4 and MKA253 were selected as sensitizers. A Stern-Volmer plot of LEG4-sensitized TiO2 substrates with a spin-coated [Ru(bpy)(3)(PF6)(2)] layer on top shows considerable quenching of the emission of the latter. Interestingly, time-resolved emission spectroscopy reveals the presence of a fast-decay time component (25 +/- 5 ns), which is absent when the anatase TiO2 semiconductor is replaced by ZrO2. It should be specified that the positive redox potential of the ruthenium complex prevents electron transfer from the [Ru(bpy)(3)(PF6)(2)] ground state into the oxidized sensitizer. Therefore, we speculate that the fast-decay time component observed stems from excited-state electron transfer from [Ru(bpy)(3)(PF6)(2)] to the oxidized sensitizer. Solid-state dye sensitized solar cells (ssDSSCs) employing MKA253 and LEG4 dyes, with [Ru(bpy)(3)(PF6)(2)] as a hole-transporting material (HTM), exhibit 1.2 % and 1.1 % power conversion efficiency, respectively. This result illustrates the possibility of the hypothesized excited-state electron transfer.
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| 23. |
- Leandri, Valentina, et al.
(författare)
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Exploring the Optical and Electrochemical Properties of Homoleptic versus Heteroleptic Diimine Copper(I) Complexes
- 2019
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Ingår i: Inorganic Chemistry. - : AMER CHEMICAL SOC. - 0020-1669 .- 1520-510X. ; 58:18, s. 12167-12177
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Tidskriftsartikel (refereegranskat)abstract
- Due to ligand scrambling, the synthesis and investigation of the properties of heteroleptic Cu(I) complexes can be a challenging task. In this work, we have studied the optical and electrochemical properties of a series of homoleptic complexes, such as [Cu(dbda)(2)](+), [Cu(dmp)(2)](+), [Cu(Br-dmp)(2)](+), [Cu(bcp)(2)](+), [Cu(dsbtmp)(2)](+), [Cu(biq)(2)](+), and [Cu(dap)(2)](+) in solution, and those of their heteroleptics [Cu(dbda)(dmp)](+), [Cu(dbda)(Br-dmp)](+), [Cu(dbda)(bcp)](+), [Cu(dbda)(dsbtmp))(+), [Cu(dbda)(biq)](+), [Cu(dbda)(dap)](+) adsorbed on the surface of anatase TiO2 (dbda = 6,6'-dimethyl-2,2'-bipyridine-4,4'-dibenzoic acid; dmp = 2,9-dimethyl-1,10-phenanthroline; Br-dmp = 5-bromo 2,9-dimethyl-1,10-phenanthroline; bcp = bathocuproine or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline; dsbtmp = 2,9-di(sec-butyl)-3,4,7,8-tetramethyl-1,10-phenanthroline; biq = 2,2'-biquinoline; dap = 2,9-dianisyl-1,10-phenanthroline). We show that the maximum absorption wavelengths of the heteroleptic complexes on TiO2 can be reasonably predicted from those of the homoleptic complexes in solution through a simple linear relation, whereas the prediction of their redox properties is less trivial. In the latter case, two different linear patterns emerge: one including the ligands bcp, biq, and dap and another one including the ligands dmp, Br-dmp, and dsbtmp. We offer an interpretation of the data based on the chemical structure of the ligands. On one hand, ligands bcp, biq, and dap possess a more extended pi-conjugated system, which gives a more prominent contribution to the overall redox properties of the ligand dbda. On the other hand, the ligands dmp, Br-dmp, and dsbtmp are all phenanthroline-based containing alkyl substituents and contribute less than dbda to the overall redox properties.
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| 24. |
- Leandri, Valentina, et al.
(författare)
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Rapid Microwave-Assisted Self-Assembly of a Carboxylic-Acid-Terminated Dye on a TiO2 Photoanode
- 2018
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Ingår i: ACS Applied Energy Materials. - : AMER CHEMICAL SOC. - 2574-0962. ; 1:1, s. 202-210
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembly of carboxylic-acid-functionalized dyes on mesoporous, anatase TiO2 is at the heart of dye-sensitized solar cells (DSSCs). However, the process often requires 6-20 h of electrode immersion at room temperature in the dye-bath solutions. Here, we introduce a new, rapid microwave-assisted sensitization technique (MINAS), which significantly accelerates the sensitization process and yields high-quality, self-assembled films of an organic dye within 5 min. Targeted experiments show that the effects of the microwave radiation cannot be explained purely on the basis of the thermal component. The interaction of the microwave radiation with the conductive fluorine-doped tin oxide (FTO) electrical contact is a key aspect to consider and a unique feature of MWAS that is the likely cause for producing rapid self-assembly of the dye on the surface.
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| 25. |
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| 26. |
- Lissau, Jonas Sandby, et al.
(författare)
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Photon Upconversion on Dye-Sensitized Nanostructured ZrO2 Films
- 2011
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:46, s. 23226-23232
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Tidskriftsartikel (refereegranskat)abstract
- Photon upconversion based on sensitized triplet?triplet annihilation has been observed on nanocrystalline ZrO2 films cosensitized with platinum(II) octaethylporphyrin (triplet sensitizer) and 9,10-diphenylanthracene (singlet emitter) under sunlight-like conditions (noncoherent excitation source, excitation light intensity as low as 5 mW/cm2). Time-resolved emission measurements showed a fast rise of the upconverted signal (≀10 ns), suggesting that triplet energy migration most probably occurs through a ?static? Dexter mechanism. To the best of our knowledge, this is the first observation of photon upconversion based on sensitized triplet?triplet annihilation on a sensitized mesoporous metal oxide. Implementation of similar systems in dye-sensitized solar cells would increase the maximum theoretical efficiency of these devices from 30% to over 40%.
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| 27. |
- Liu, Jianhua, et al.
(författare)
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Metal nanowire networks : Recent advances and challenges for new generation photovoltaics
- 2019
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Ingår i: Materials Today Energy. - : ELSEVIER SCI LTD. - 2468-6069. ; 13, s. 152-185
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Forskningsöversikt (refereegranskat)abstract
- Transparent conducting electrodes which allow photons passing through and simultaneously transfers the charge carriers are critical for the construction of high-performance photovoltaic cells. Electrodes based on metal oxides, such as indium-doped tin oxide (ITO) or fluorine-doped tin oxide (FTO), may have limited application in new generation flexible solar cells, which employ solution-processed roll-to-roll or ink-printing techniques toward large-area-fabrication approach, due to their brittleness and poor mechanical properties. Metal nanowire network (MNWN) emerges as a highly potential alternative candidate instead of ITO or FTO due to the high transparency, low sheet resistance, low cost, solution processable and compatibility with a flexible substrate for high throughput production. This feature article systematically summarizes the recent advances of the MNWNs, including new concepts and emerging strategies for the synthesis of metal nanowires (MNWs), various approaches for the preparation of MNWNs and comprehensively discusses the novel MNWN electrodes prepared on different substrates. The state-of-the-art new generation solar cell devices, such as transparent, flexible and light-weight solar cells, with MNWN as a transparent conductive electrode are emphasized. Finally, the opportunities and challenges for the development of MNWN electrodes toward application in the new generations of photovoltaic devices are discussed.
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| 28. |
- Liu, Peng, et al.
(författare)
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Cross-linked sulfur-selenium polymers as hole transporting materials in dye-sensitized solar cells and perovskite solar cells
- 2017
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Ingår i: ChemPhotoChem. - : Wiley-VCH Verlagsgesellschaft. - 2367-0932. ; 1:8, s. 363-368
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Tidskriftsartikel (refereegranskat)abstract
- Novel inverse-vulcanized polymeric sulfur–selenium materials (SeS2:S:DIB, where DIB=1,3-diisopropenylbenzene) have been prepared and utilized for solid-state dye-sensitized solar cellsand perovskite solar cells. Under standard AM 1.5G illumination (1000 Wm-2), a power conversion efficiency of 1.70% was recorded for polymeric sulfur–selenium–based (SeS2:S:DIB) solidstate solar cells, which is higher than that of polymeric sulfurbased (S:DIB) devices (1.09 %). For perovskite solar cells, a relatively high efficiency has been achieved for polymeric sulfur–selenium-based (SeS2:S:DIB) solar cells (10.21%) and polymeric sulfur-based (S:DIB; 7.32%) solar cells, respectively. The conductivity of the polymeric SeS material has been determined to 2.2410-4 Scm-1, which is higher than for the polymeric sulfur material under the same doping conditions. Photoinduced absorption and steady-state photoluminescence measurements were performed to investigate the charge-transfer properties relevant for the solar cells. The results in the present study qualify the new polymeric sulfur–selenium materials as candidates for low-cost hole-transport materials for photovoltaic devices.
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| 29. |
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| 30. |
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| 31. |
- Ma, Yiqian, et al.
(författare)
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Application of Eutectic Freeze Crystallization in the Recycling of Li-Ion Batteries
- 2021
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Ingår i: Rare Metal Technology 2021. - Cham : Springer Nature. ; , s. 3-10
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Konferensbidrag (refereegranskat)abstract
- The widespread and increasing use of Li-ion batteries has led to an impending need for recycling solutions. Consequently, recycling of spent Li-ion batteries with energy-efficient, environmentally sustainable strategies has become a research hotspot. In this work, eutectic freeze crystallization (EFC), which requires less energy input than conventional evaporative crystallization (EC), has been investigated as a method for the recovery of Ni and Co sulfates from synthetic acidic strip solution in the recycling of NMC or NCA Li-ion batteries. Two binary sulfate systems have been studied. Batch EFC experiments have been conducted. It is shown that, with suitable control of supersaturation, ice and salt crystals can be recovered as separate phases below the eutectic temperatures. The work shows that EFC is a promising alternative to EC for the recovery of Ni and Co sulfates from spent Li-ion batteries.
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| 32. |
- Ma, Yiqian, et al.
(författare)
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Eutectic Freeze Crystallization for Recovery of Cobalt Sulfate in the Recycling of Li-Ion Batteries
- 2023
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Ingår i: Rare Metal Technology 2023. - Cham : Springer.
-
Konferensbidrag (refereegranskat)abstract
- Crystallization of cobalt sulfate within a typical hydrometallurgical process for the recycling of Ni-Mn-Co oxide or Ni-Co-Al oxide Li-ion batteries has been investigated. The cobalt sulfate salt was obtained by eutectic freeze crystallization (EFC) from a synthetic acidic cobalt strip liquor after solvent extraction. The ternary phase diagram of CoSO4–H2SO4–H2O was first established by the mixed-solvent electrolyte (MSE) model to predict and reveal the changes in the system during the freezing process and to assess the conditions required for EFC. Batch EFC experiments were then conducted for the cobalt strip liquor, which contained a low concentration of impurities. It is shown that with suitable control of supersaturation, seeding, and stirring, pure ice and salt crystals can be recovered as separate phases at the eutectic temperatures, with the crystalline salts in the form of a heptahydrate. The crystallization process can be described using the ternary phase diagram, but with certain deviations. The deviations might be related to insufficient data at the low temperatures in the MSE model and acid entrapment in crystals during the crystallization process. Finally, the performance of the EFC process has been compared to that of an evaporative crystallization (EC) using the same strip liquor. It was found that the CoSO4·7H2O product obtained by EFC was of slightly higher quality considering purity and crystal shape compared to that from EC.
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| 33. |
- Ma, Yiqian, et al.
(författare)
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Eutectic freeze crystallization for recovery of NiSO4 and CoSO4 hydrates from sulfate solutions
- 2022
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Ingår i: Separation and Purification Technology. - : Elsevier BV. - 1383-5866 .- 1873-3794. ; 286
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Tidskriftsartikel (refereegranskat)abstract
- In this study, eutectic freeze crystallization (EFC) was investigated to recover NiSO4 and CoSO4 hydrates from aqueous and dilute sulfuric acid solutions of metal sulfates. Binary phase diagrams were established using a combination of thermodynamic modeling and experimental data. The mixed-solvent electrolyte (MSE) model was employed to model solid–liquid phase equilibria. The predicted binary phase diagrams from the model were in good agreement with the experimental results. Experimental eutectic temperatures and eutectic metal sulfate concentrations for the NiSO4-H2O and CoSO4-H2O systems are −3.3 °C and 20.8 wt% and −2.9 °C and 19.3 wt%, respectively. For NiSO4-H2SO4-H2O and CoSO4-H2SO4-H2O systems, the eutectic temperature and eutectic metal sulfate concentration decrease with increasing H2SO4 concentration. Batch experiments were performed to study the EFC of different sulfate solutions, including 25- wt% NiSO4 in H2O, 20- wt% NiSO4 in 0.5 mol/kg H2SO4, 25- wt% CoSO4 in H2O, and 20- wt% CoSO4 in 0.5 mol/kg H2SO4. The results show that controlling the supersaturation allows high-quality ice and salt crystals to be recovered as separate phases under eutectic conditions, with the crystalline salts in the form of heptahydrates. This study shows that EFC can be a promising alternative to evaporative crystallization for recovering NiSO4 and CoSO4 hydrates from sulfate solutions.
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| 34. |
- Ma, Yiqian, et al.
(författare)
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Phase diagrams of CoSO4-H2O and CoSO4-H2SO4-H2O systems for CoSO4·nH2O (n = 6,7) recovery by cooling and eutectic freeze crystallization
- 2024
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Ingår i: Hydrometallurgy. - : Elsevier BV. - 0304-386X .- 1879-1158. ; 227
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports the solid-liquid phase equilibria of the CoSO4-H2O and CoSO4-H2SO4-H2O systems at low temperatures. Binary and ternary phase diagrams, including the stable solid phases CoSO4·6H2O and CoSO4·7H2O were established using experimental data and thermodynamic modeling applying the mixed-solvent electrolyte (MSE) model. The results showed that the addition of H2SO4 shifts the eutectic temperature and concentration to lower values for cobalt sulfate and ice crystallization. The trends obtained from the experimental data and the modeling are consistent for the binary CoSO4-H2O system with good agreement, but the ternary CoSO4-H2SO4-H2O system shows some deviations. In general, the MSE model is shown to be reliable for inferring and establishing the phase diagram of the low-temperature system. The phase diagrams are helpful for designing the pathways of cooling crystallization and eutectic freeze crystallization and assessing the performance of the low-temperature crystallization process in the production of CoSO4 hydrates. In addition, some practical examples of cooling crystallization and eutectic freeze crystallization of CoSO4 solutions are provided.
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| 35. |
- Ma, Yiqian, et al.
(författare)
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Precipitation and crystallization used in the production of metal salts for Li-ion battery materials : A review
- 2020
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 10:12
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Forskningsöversikt (refereegranskat)abstract
- Li-ion battery materials have been widely studied over the past decades. The metal salts that serve as starting materials for cathode and production, including Li2CO3, NiSO4, CoSO4 and MnSO4, are mainly produced using hydrometallurgical processes. In hydrometallurgy, aqueous precipitation and crystallization are important unit operations. Precipitation is mainly used in the processes of impurity removal, separation and preliminary production, while controlled crystallization can be very important to produce a pure product that separates well from the liquid solution. Precipitation and crystallization are often considered in the development of sustainable technologies, and there is still room for applying novel techniques. This review focuses on precipitation and crystallization applied to the production of metal salts for Li-ion battery materials. A number of novel and promising precipitation and crystallization methods, including eutectic freeze crystallization, antisolvent crystallization, and homogeneous precipitation are discussed. Finally, the application of precipitation and crystallization techniques in hydrometallurgical recycling processes for Li-ion batteries are reviewed.
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| 36. |
- Phuyal, Dibya, 1985-, et al.
(författare)
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Electronic Structure of Two-Dimensional Lead(II) Iodide Perovskites : An Experimental and Theoretical Study
- 2018
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 30:15, s. 4959-4967
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 37. |
- Sadollahkhani, Azar, et al.
(författare)
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Energetic Barriers to Interfacial Charge Transfer and Ion Movement in Perovskite Solar Cells
- 2017
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Ingår i: ChemPhysChem. - : WILEY-V C H VERLAG GMBH. - 1439-4235 .- 1439-7641. ; 18:21, s. 3047-3055
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Tidskriftsartikel (refereegranskat)abstract
- Highly efficient perovskite solar cells have been characterized by current-density/voltage measurements in the dark at varied scan rates. The results were compared to the solar cells without a hole-transporting layer to investigate the role of ultrathin hole-transporting layers in solar-cell function. The parameters of internal voltage, diode ideality factor, capacitive current, and capacitance were calculated from the current-density/voltage response of the cells in the dark. The results show that the absence of the hole-transporting layer can cause a large recombination current within the depletion region at the gold contact/perovskite interface, and thus affects the cell performance.
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| 38. |
- Sahadevan, Suchithra Ashoka, et al.
(författare)
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Sulfur-Oleylamine Copolymer Synthesized via Inverse Vulcanization for the Selective Recovery of Copper from Lithium-Ion Battery E-Waste
- 2023
-
Ingår i: Materials Chemistry Frontiers. - : Royal Society of Chemistry (RSC). - 2052-1537.
-
Tidskriftsartikel (refereegranskat)abstract
- Elemental sulfur (S8) is an abundant and inexpensive by-product of petroleum refining. Polymeric sulfur is thermodynamically unstable and depolymerizes back to S8 with time, which limits its applications and causes megatons of sulfur to accumulate in nature. A novel sulfur-oleylamine copolymer, synthesized using the inverse vulcanization method, is reported for the selective recovery of Cu2+ from a complex mixture of transition metals. Adsorption studies have been performed using batch experiments in the simulated aqueous solution containing a mix of metal ions (Mx+= Fe, Al, Mn, Co, Ni and Cu). The effect of different adsorption parameters such as pH, time, adsorbent dose, sulfur content, and desorption have been studied. The results demonstrate that the sulfur-oleylamine copolymer shows high selectivity towards Cu2+, with excellent adsorption efficiency of >98 % in acidic pH (pH≈1) at room temperature, which is of practical relevance in the handling of battery leach liquors obtained from industrially derived blackmass. Finally, the sulfur-oleylamine copolymers were also applied to battery leach liquors with hydrochloric (HCl) or citric acid and which showed Cu2+ adsorption efficiency of >98 %±1 and > 95 %±7, respectively. This work presents a novel way to convert industrial waste into a stable sulfur polymer and demonstrates its use as a promising material for selective recovery of Cu ions from battery waste and industrial effluents in a simple and cost-effective manner.
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| 39. |
- Shatskiy, Andrey, et al.
(författare)
-
Back cover
- 2021
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Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 12:15, s. 5430-5437
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Tidskriftsartikel (refereegranskat)
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| 40. |
- Wang, Linqin, et al.
(författare)
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A crosslinked polymer as dopant-free hole-transport material for efficient n-i-p type perovskite solar cells
- 2021
-
Ingår i: Journal of Energy Chemistry. - : Elsevier BV. - 2095-4956 .- 2096-885X. ; 55, s. 211-218
-
Tidskriftsartikel (refereegranskat)abstract
- A new crosslinked polymer, called P65, with appropriate photo-electrochemical, opto-electronic, and thermal properties, has been designed and synthesized as an efficient, dopant-free, hole-transport material (HTM) for n-i-p type planar perovskite solar cells (PSCs). P65 is obtained from a low-cost and easily synthesized spiro[fluorene-9,9′-xanthene]-3′,6′-diol (SFX-OH)-based monomer X65 through a free-radical polymerization reaction. The combination of a three-dimensional (3D) SFX core unit, hole-transport methoxydiphenylamine group, and crosslinked polyvinyl network provides P65 with good solubility and excellent film-forming properties. By employing P65 as a dopant-free hole-transport layer in conventional n-i-p type PSCs, a power conversion efficiency (PCE) of up to 17.7% is achieved. To the best of our knowledge, this is the first time a 3D, crosslinked, polymeric dopant-free HTM has been reported for use in conventional n-i-p type PSCs. This study provides a new strategy for the future development of a 3D crosslinked polymeric dopant-free HTM with a simple synthetic route and low-cost for commercial, large-scale applications in future PSCs.
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| 41. |
- Xiao, Xiong, et al.
(författare)
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Ultrasound-assisted extraction of metals from Lithium-ion batteries using natural organic acids
- 2021
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Ingår i: Green Chemistry. - : Royal Society of Chemistry (RSC). - 1463-9262 .- 1463-9270. ; 23:21
-
Tidskriftsartikel (refereegranskat)abstract
- An ultrasound-assisted extraction (leaching) method of valuable metals from discarded lithium-ion batteries (LiBs) is reported. Mild organic citric or acetic acids were used as leaching agents for a more environmentally-friendly recovery of the lithium, nickel, cobalt, and manganese from the discharged and crushed lithium nickel-manganese-cobalt oxide (NMC) LiBs. The extraction was performed with the presence/absence of continuous ultrasound (US) energy supplied by a 110 W ultrasonic bath. The effect of temperature (30-70 °C), reducing agent concentration (H2O2: 0-2.0 vol%), as well as choice of specific acid on the metal dissolution were investigated. The US leaching decreased the leaching time by more than 50% and improved the leached percentage of Li, Mn, Co, and Ni due to the local heat and improved mass transfer between solid and liquid interfaces in the process. The X-ray diffraction results of residues from the US leaching further confirmed an improved dissolution of the crushed layered NMC structure, resulting in the significant improvement of the leached amounts of the valuable metals. Furthermore, it is demonstrated that using citric acid eliminated the need of additional reducing agents and suppressed the dissolution of copper (Cu) due to its inhibitor effect on the Cu surface, i.e. compared with using acetic acid as leaching reagent. Overall, it is shown that recovery of the battery metals can be facilitated and carried out in a more energy-efficient manner at low temperatures (50 °C) using ultrasound to improve metal ions mass transportation in the residue layers of the NMC during the organic acid leaching.
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| 42. |
- Yao, Zhaoyang, et al.
(författare)
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Conformational and Compositional Tuning of Phenanthrocarbazole-Based Dopant-Free Hole-Transport Polymers Boosting the Performance of Perovskite Solar Cells
- 2020
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 142:41, s. 17681-17692
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Tidskriftsartikel (refereegranskat)abstract
- Conjugated polymers are regarded as promising candidates for dopant-free hole-transport materials (HTMs) in efficient and stable perovskite solar cells (PSCs). Thus far, the vast majority of polymeric HTMs feature structurally complicated benzo[1,2-b:4,5-b']dithiophene (BDT) analogs and electron-withdrawing heterocycles, forming a strong donor-acceptor (D-A) structure. Herein, a new class of phenanthrocarbazole (PC)-based polymeric HTMs (PC1, PC2, and PC3) has been synthesized by inserting a PC unit into a polymeric thiophene or selenophene chain with the aim of enhancing the pi-pi stacking of adjacent polymer chains and also to efficiently interact with the perovskite surface through the broad and planar conjugated backbone of the PC. Suitable energy levels, excellent thermostability, and humidity resistivity together with remarkable photoelectric properties are obtained via meticulously tuning the conformation and elemental composition of the polymers. As a result, PSCs containing PC3 as dopant-free HTM show a stabilized power conversion efficiency (PCE) of 20.8% and significantly enhanced longevity, rendering one of the best types of PSCs based on dopant-free HTMs. Subsequent experimental and theoretical studies reveal that the planar conformation of the polymers contributes to an ordered and face-on stacking of the polymer chains. Furthermore, introduction of the "Lewis soft" selenium atom can passivate surface trap sites of perovskite films by Pb-Se interaction and facilitate the interfacial charge separation significantly. This work reveals the guiding principles for rational design of dopant-free polymeric HTMs and also inspires rational exploration of small molecular HTMs.
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| 43. |
- Zhang, Fuguo, et al.
(författare)
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Polymeric, Cost-Effective, Dopant-Free Hole Transport Materials for Efficient and Stable Perovskite Solar Cells
- 2019
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 141:50, s. 19700-19707
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Tidskriftsartikel (refereegranskat)abstract
- Perovskite solar cells (PSCs) has skyrocketed in the past decade to an unprecedented level due to their outstanding photoelectric properties and facile processability. However, the utilization of expensive hole transport materials (HTMs) and the inevitable instability instigated by the deliquescent dopants represent major concerns hindering further commercialization. Here, a series of low-cost, conjugated polymers are designed and applied as dopant-free HTMs in PSCs, featuring tuned energy levels, good temperature and humidity resistivity, and excellent photoelectric properties. Further studies highlight the critical and multifaceted roles of the polymers with respect to facilitating charge separation, passivating the surface trap sites of perovskite materials, and guaranteeing long-term stability of the devices. A stabilized power conversion efficiency (PCE) of 20.3% and remarkably enhanced device longevity are achieved using the dopant-free polymer P3 with a low concentration of 5 mg/mL, qualifying the device as one of the best PSC systems constructed on the basis of dopant-free HTMs so far. In addition, the flexible PSCs based on P3 also exhibit a PCE of 16.2%. This work demonstrates a promising route toward commercially viable, stable, and efficient PSCs.
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| 44. |
- Zhang, Wei, et al.
(författare)
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Mechanistic Insights from Functional Group Exchange Surface Passivation : A Combined Theoretical and Experimental Study
- 2019
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Ingår i: ACS Applied Energy Materials. - : AMER CHEMICAL SOC. - 2574-0962. ; 2:4, s. 2723-2733
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Tidskriftsartikel (refereegranskat)abstract
- Four different functional groups including amino (-NH2), phosphine (-PH2), hydroxyl (-OH), and thiol (-SH) were combined with POSS (polyhedral oligomeric silsesquioxane) molecules to investigate how functional groups affect the surface passivation of POSS systems. Results from density-functional theory (DFT) calculations indicate that functional group amino (-NH2) with adsorption energy 86 (56) kJ mol(-1) is consistently better than that of thiol (-SH) with adsorption energy 68 (43) kJ mor(-1) for different passivation mechanisms. Theoretical studies on the analogous POSS-OH and POSS-PH2 systems show similar adsorption energies. Two of the systems were also investigated experimentally; aminopropyl isobutyl POSS (POSS-NH2) and mercaptopropyl isobutyl POSS (POSS-SH) were applied as passivation materials for MAPbI(3) (MA = methylammonium) perovskite and (FA)(0.85)(MA)(0.15)Pb(I-3)(0.85)(Br-3)(0)(.15)(FA = formamidinium) perovskite films. The same conclusion was drawn based on the results from contact angle studies, X-ray diffraction (XRD), and the stability of solar cells in ambient atmosphere, indicating the vital importance of choice of functional groups for passivation of the perovskite materials.
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| 45. |
- Zhang, Wei, et al.
(författare)
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Organic Salts as p-Type Dopants for Efficient LiTFSI-Free Perovskite Solar Cells
- 2020
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 12:30, s. 33751-33758
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Tidskriftsartikel (refereegranskat)abstract
- Despite the ubiquity and importance of organic hole-transport materials in photovoltaic devices, their intrinsic low conductivity remains a drawback. Thus, chemical doping is an indispensable solution to this drawback and is essentially always required. The most widely used p-type dopant, FK209, is a cobalt coordination complex. By reducing Co(III) to Co(II), Spiro-OMeTAD becomes partially oxidized, and the film conductivity is initially increased. In order to further increase the conductivity, the hygroscopic co-dopant LiTFSI is typically needed. However, lithium salts are normally quite hygroscopic, and thus, water absorption has been suggested as a significant reason for perovskite degradation and therefore limited device stability. In this work, we report a LiTFSI-free doping process by applying organic salts in relatively high amounts. The film conductivity and morphology have been studied at different doping amounts. The resulting solar cell devices show comparable power conversion efficiencies to those based on conventional LiTFSI-doped Spiro-OMeTAD but show considerably better long-term device stability in an ambient atmosphere.
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| 46. |
- Zhang, Wei, 1989-, et al.
(författare)
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Single crystal structure and opto-electronic properties of oxidized Spiro-OMeTAD
- 2020
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Ingår i: Chemical Communications. - : Royal Society of Chemistry. - 1359-7345 .- 1364-548X. ; 56:10, s. 1589-1592
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Tidskriftsartikel (refereegranskat)abstract
- Single crystals of Spiro(TFSI)2 were grown, the optical and electronic properties were characterized and compared with neutral Spiro-OMeTAD. Density-functional theory was used to get insights into binding and band structure properties. The flat valence bands indicate a rather limited orbital overlap in Spiro(TFSI)2.
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| 47. |
- Zhang, Wei, et al.
(författare)
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The Central Role of Ligand Conjugation for Properties of Coordination Complexes as Hole-Transport Materials in Perovskite Solar Cells
- 2019
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Ingår i: ACS Applied Energy Materials. - : AMER CHEMICAL SOC. - 2574-0962. ; 2:9, s. 6768-6779
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Tidskriftsartikel (refereegranskat)abstract
- Two zinc-based coordination complexes Y3 and Y4 have been synthesized and characterized, and their performance as hole-transport materials (HTMs) for perovskite solar cells (PSCs) has been investigated. The complex Y3 contains two separate ligands, and the molecular structure can be seen as a disconnected porphyrin ring. On the other hand, Y4 consists of a porphyrin core and therefore is a more extended conjugated system as compared to Y3. The optical and redox properties of the two different molecular complexes are comparable. However, the hole mobility and conductivity of Y4 as macroscopic material are remarkably higher than that of Y3. Furthermore, when employed as hole-transport materials in perovskite solar cells, cells containing Y4 show a power conversion efficiency (PCE) of 16.05%, comparable to the Spiro-OMeTAD-based solar cells with an efficiency around 17.08%. In contrast, solar cells based on Y3 show a negligible efficiency of about 0.01%. The difference in performance of Y3 and Y4 is analyzed and can be attributed to the difference in packing of the nonplanar and planar building blocks in the corresponding materials.
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