| 1. |
- Cao, Wei, et al.
(författare)
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Spray-Deposited Anisotropic Ferromagnetic Hybrid Polymer Films of PS-b-PMMA and Strontium Hexaferrite Magnetic Nanoplatelets
- 2021
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 13:1, s. 1592-1602
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Tidskriftsartikel (refereegranskat)abstract
- Spray deposition is a scalable and cost-effective technique for the fabrication of magnetic hybrid films containing diblock copolymers (DBCs) and magnetic nanoparticles. However, it is challenging to obtain spray-deposited anisotropic magnetic hybrid films without using external magnetic fields. In the present work, spray deposition is applied to prepare perpendicular anisotropic magnetic hybrid films by controlling the orientation of strontium hexaferrite nanoplatelets inside ultra-high-molecular-weight DBC polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) films. During spray deposition, the evolution of DBC morphology and the orientation of magnetic nanoplatelets are monitored with in situ grazing-incidence small-angle X-ray scattering (GISAXS). For reference, a pure DBC film without nanoplatelets is deposited with the same conditions. Solvent-controlled magnetic properties of the hybrid film are proven with solvent vapor annealing (SVA) applied to the final deposited magnetic films. Obvious changes in the DBC morphology and nanoplatelet localization are observed during SVA. The superconducting quantum interference device data show that ferromagnetic hybrid polymer films with high coercivity can be achieved via spray deposition. The hybrid films show a perpendicular magnetic anisotropy before SVA, which is strongly weakened after SVA. The spray-deposited hybrid films appear highly promising for potential applications in magnetic data storage and sensors.
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| 2. |
- Heger, Julian E., et al.
(författare)
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Superlattice deformation in quantum dot films on flexible substrates via uniaxial strain
- 2023
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Ingår i: Nanoscale Horizons. - : Royal Society of Chemistry (RSC). - 2055-6764 .- 2055-6756. ; 8:3, s. 383-395
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Tidskriftsartikel (refereegranskat)abstract
- The superlattice in a quantum dot (QD) film on a flexible substrate deformed by uniaxial strain shows a phase transition in unit cell symmetry. With increasing uniaxial strain, the QD superlattice unit cell changes from tetragonal to cubic to tetragonal phase as measured with in situ grazing-incidence small-angle X-ray scattering (GISAXS). The respective changes in the optoelectronic coupling are probed with photoluminescence (PL) measurements. The PL emission intensity follows the phase transition due to the resulting changing inter-dot distances. The changes in PL intensity accompany a redshift in the emission spectrum, which agrees with the Forster resonance energy transfer (FRET) theory. The results are essential for a fundamental understanding of the impact of strain on the performance of flexible devices based on QD films, such as wearable electronics and next-generation solar cells on flexible substrates.
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| 3. |
- Yin, Shanshan, et al.
(författare)
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Tailored fabrication of quasi-isoporous and double layered alpha-Fe2O3 thin films and their application in photovoltaic devices
- 2023
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 455, s. 140135-
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Tidskriftsartikel (refereegranskat)abstract
- A series of α-Fe2O3 thin films with distinct morphologies are prepared via a facile polystyrene-block-polyethylene oxide templated sol–gel method. By tailoring the poor solvent contents and FeCl3-to-polymer weight ratio in the sol–gel solutions, quasi-isoporous α-Fe2O3 thin films with different substructures and thicknesses are obtained. Via a thermal annealing post-treatment, double layered structures are induced by a synergistic dewetting and Oswald ripening effect. Special focus is set on the α-Fe2O3 thin films prepared with no annealing/annealing-medium FeCl3 concentration, as they possess uniform periodic structures, which is suitable to be used as hole blocking modification layer of perovskite solar cells (PSCs). An improved power conversion efficiency (PCE) is obtained when the double layered α-Fe2O3 thin film is applied as the hole blocking modification layer for PSCs. The improved PCE primarily originates from the increased VOC, which probably benefits from the synergistic effect of the suppressed charge carrier recombination at the interfaces, the enhanced light transmittance as well as the superior electron extraction capacity.
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| 4. |
- Zou, Yuqin, et al.
(författare)
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Ionic liquids tailoring crystal orientation and electronic properties for stable perovskite solar cells
- 2023
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Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855 .- 2211-3282. ; 112, s. 108449-108449
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Tidskriftsartikel (refereegranskat)abstract
- The crystallization behavior of perovskite films has a profound influence on the resulting defect densities, charge carrier dynamics and photovoltaic performance. Herein, we introduce ionic liquids into the perovskite component to tailor the crystal growth of perovskite films from a disordered to a preferential corner-up orientation and accordingly increase the charge carrier mobility to accelerate electron transport and extraction. Using time-resolved measurements, we probe the charge carrier generation, transport and recombination behavior in these films and related devices. We find the ionic liquid-containing samples exhibit lower defects, faster charge carrier transport and suppressed non-radiative recombination, contributing to higher efficiency and fill factor. Via operando grazing-incidence small- and wide-angle X-ray scattering measurements, we observe a light-induced lattice compression and grain fragmentation in the control devices, whereas the ionic liquid-containing devices exhibit a slight light-induced crystal reconstitution and stronger tolerance against illumination. Under ambient conditions, the non-encapsulated device with the pyrrolidinium-based ionic compound (Pyr14BF4) maintains 97% of its initial efficiency after 4368 h.
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