Haifeng Yuan

Haifeng Yuan
KU Leuven | ku leuven

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84
Publications
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Publications

Publications (84)
Article
The excellent optoelectronic properties of metal halide perovskites (MHPs) have been employed in various photocatalytic applications, but their poor water stability is considered as the main bottleneck for further development. Herein, we protect the light-absorbing CsPbBr3 MHP with a NiOx and TiO2 hole and electron extracting layer. This planar NiO...
Article
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Controlling grain orientations within polycrystalline all‐inorganic halide perovskite solar cells can help increase conversion efficiencies toward their thermodynamic limits; however, the forces governing texture formation are ambiguous. Using synchrotron X‐ray diffraction, mesostructure formation within polycrystalline CsPbI2.85Br0.15 powders as t...
Preprint
Controlling grain orientations within polycrystalline all-inorganic halide perovskite solar cells can help increase conversion efficiencies toward their thermodynamic limits, however the forces governing texture formation are ambiguous. Using synchrotron X-ray diffraction, we report meso-structure formation within polycrystalline CsPbI2.85Br0.15 po...
Article
Mapping the spatial and temporal heterogeneities in miscible polymer blends is critical for understanding and further improving their material properties. However, a complete picture on the heterogeneous dynamics is often obscured in ensemble measurements. Herein, the spatial and temporal heterogeneities in fully miscible polystyrene/oligostyrene b...
Article
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Graphene, a single atomic layer of sp² hybridized carbon, is a promising material for future devices due to excellent optical and electrical properties. Nevertheless, for practical applications, it is essential to deposit patterned metal on graphene in the micro and nano-meter scale in order to inject electrodes or modify the 2D film electrical pro...
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Reduced-dimensional perovskites are attractive light-emitting materials due to their efficient luminescence, color purity, tunable bandgap, and structural diversity. A major limitation in perovskite light-emitting diodes is their limited operational stability. Here we demonstrate that rapid photodegradation arises from edge-initiated photooxidation...
Article
Defect engineering in photocatalysts represents a fundamental method toward tailoring their solar-to-chemical energy conversion performance, although determining the nature and impact of subsurface defects remains challenging. Single-unit-cell Bi2WO6 monolayers – forming a sandwich-like structure; [BiO]⁺–[WO4]²−–[BiO]⁺ – exhibit promising photocata...
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An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Article
The optoelectronic properties of lead halide perovskites strongly depend on their underlying crystal symmetries and dynamics, sometimes exhibiting a dual photoluminescence (PL) emission via Rashba-like effects. Here we exploit spin- and temperature-dependent PL to study single crystal APbBr3 (A= Cs and methylammonium; CH3NH3) and evaluate peak ener...
Article
Metal trihalide perovskites are rapidly redefining the landscape of solid-state semiconductors utilized as active medium in photovoltaics and in light generation. Within this materials space, organic-inorganic hybrid formamidinium lead bromide (FAPbBr3) has arisen as a promising candidate for efferent light emitting devices, due to its capacity for...
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The high-temperature all-inorganic CsPbI 3 perovskite black phase is metastable relative to its yellow non-perovskite phase, at room temperature. Since only the black phase is optically active, this represents an impediment for the use of CsPbI 3 in optoelectronic devices. We report the use of substrate clamping and biaxial strain to render stable,...
Article
Developing simple and cost‐efficient methods for fabricating molecular patterns is of great importance in the field of nanoscience and nanotechnology. Here, a simple and convenient method was developed for fabricating nanopatterns composed of positively charged silane molecules by using silver nanowires as templates. The as‐obtained silane pattern...
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The extraordinary properties of lead‐halide perovskite materials have spurred intense research, as they have a realistic perspective to play an important role in future photovoltaic devices. It is known that these materials undergo a number of structural phase transitions as a function of temperature that markedly alter their optical and electronic...
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The original version of this article incorrectly listed the present address of Bo Wu as ‘Present address: Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, Guangdong Province 510006, China’. This is the author’s primary affiliation. This has been corrected in both the...
Article
This special issue on Perovskite Nanocrystals is guest edited by Maarten B. J. Roeffaers and Johan Hofkens. Read more about the exciting papers in the issue in this editorial.
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Halide perovskites possess enormous potential for various optoelectronic applications. Presently, a clear understanding of the interplay between the lattice and electronic effects is still elusive. Specifically, the weakly absorbing tail states and dual emission from perovskites are not satisfactorily described by existing theories based on the Urb...
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Inspired by the efficient perovskite solar cells, we developed a three-component hybrid perovskite-based solar photocatalyst cell - NiOx/FAPbBr3/TiO2 - for C(sp³)-H bonds activation with high selectivity (~90%) and high conversion rates (3800 µmol g⁻¹ h⁻¹) under ambient conditions. Time-resolved spectroscopy on our photocatalytic cell reveals effic...
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Developments in microscopy have been instrumental to progress in the life sciences, and many new techniques have been introduced and led to new discoveries throughout the last century. A wide and diverse range of methodologies is now available, including electron microscopy, atomic force microscopy, magnetic resonance imaging, small-angle x-ray sca...
Article
The sensitive detection of X‐rays embodies an important research area, being motivated by a common desire to minimize the radiation doses required for detection. In article number 1804550, Julian A. Steele, Maarten B. J. Roeffaers, and co‐workers detail the photophysical properties contributing to the impressive performance of highly sensitive X‐ra...
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The electrochemical reduction of CO2 to multi-carbon products has attracted much attention because it provides an avenue to the synthesis of value-added carbon-based fuels and feedstocks using renewable electricity. Unfortunately, the efficiency of CO2 conversion to C2 products remains below that necessary for its implementation at scale. Modifying...
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Hybrid organic–inorganic perovskites exhibit strong spin–orbit coupling¹, spin-dependent optical selection rules2,3 and large Rashba splitting4–8. These characteristics make them promising candidates for spintronic devices⁹ with photonic interfaces. Here we report that spin polarization in perovskites can be controlled through chemical design as we...
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The sensitive detection of X‐rays embodies an important research area, being motivated by a common desire to minimize the radiation doses required for detection. Among metal halide perovskites, the double‐perovskite Cs2AgBiBr6 system has emerged as a promising candidate for the detection of X‐rays, capable of high X‐ray stability and sensitivity (1...
Article
The room-temperature charge carrier mobility and excitation-emission properties of metal halide perovskites are governed by the electronic band structure and intrinsic lattice phonon scattering mechanisms. Establishing how charge carriers interact within this scenario will have far-reaching consequences for developing high-effciency materials for o...
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Efficient wide-bandgap perovskite solar cells (PSCs) enable high-efficiency tandem photovoltaics when combined with crystalline silicon and other low-bandgap absorbers. However, wide-bandgap PSCs today exhibit performance far inferior to that of sub-1.6-eV bandgap PSCs due to their tendency to form a high density of deep traps. Here, we show that h...
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Formamidinium-lead-iodide (FAPbI3)-based perovskites with bandgap below 1.55 eV are of interest for photovoltaics in view of their close-to-ideal bandgap. Record-performance FAPbI3-based solar cells have relied on fabrication via the sequential-deposition method; however, these devices exhibit unstable output under illumination due to the difficult...
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The impressive optoelectronic performance and low production cost of metal halide perovskites have inspired applications well beyond efficient so-lar cells. Herein, we widen the materials engineer-ing options available for the efficient and selective photocatalytic oxidation of benzylic alcohols - an industrially significant reaction - using forma-...
Article
Organic-inorganic halide perovskites (OIHPs) have demonstrated outstanding energy conversion efficiency in solar cells and light-emitting devices. In spite of intensive developments in both materials and devices, electronic traps and defects that significantly affect their device properties remain under-investigated. Particularly, it remains challe...
Article
The optoelectronic properties and charge carrier dynamics in hybrid organic-inorganic perovskites under steady-state illumination are the key elements towards understanding their high efficiency. We present temperature-dependent Hall and photo-conductivity measurements down to a temperature of 4.2 K on single crystals of MAPbI3 and MAPbBr3 in magne...
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In the presence of disorder, superconductivity exhibits short-range characteristics linked to localized Cooper pairs which are responsible for anomalous phase transitions and the emergence of quantum states such as the bosonic insulating state. Complementary to well-studied homogeneously disordered superconductors, superconductor-normal hybrid arra...
Article
A Highly reproducible and controllable deposition procedure for gold nanostructures on a titanium dioxide (TiO2) surface using femtosecond laser light is demonstrated. This is realized by precise focusing onto the TiO2 surface in the presence of pure gold ion solution. The deposition is demonstrated both in dot array and line structures. Thanks to...
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Organolead halide perovskites are increasingly considered for applications well beyond photo-voltaics, for example, as the active regions within photonic devices. Herein, we report the direct laser write (DLW: 458nm cw-laser) of the formamidinium lead iodide (FAPbI3) yellow δ-phase into its high-temperature luminescent black α-phase; a remarkably e...
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In this work, we reveal nanoscale morphological changes on the surface of a silver nanowire (AgNW) in the conventional surface-enhanced Raman scattering (SERS) measurement condition. The surface morphology changes are due to the surface plasmon-promoted photochemical etching of silver in the presence of certain Raman probes, resulting in a dramatic...
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Superconductivity and ferromagnetism are two mutually antagonistic states in condensed matter. Research on the interplay between these two competing orderings sheds light not only on the cause of various quantum phenomena in strongly correlated systems but also on the general mechanism of superconductivity. Here we report on the observation of the...
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Controlling morphology of organolead halide perovskite crystals is crucial to a fundamental understanding of the materials and to tune their properties for device applications. Here, we report a facile solution-based method for morphology-controlled synthesis of rod-like and plate-like organolead halide perovskite nanocrystals using the binary capp...
Article
Photocatalytic reactions occur at the crystal-solution interface, hence specific crystal facet expression and surface defects can play an important role. Here, we investigate the structure related photoreduction at zinc oxide (ZnO) microparticles, via integrated light- and electron microscopy in combination with silver metal photodeposition. This e...
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Photoluminescence (PL) of organometal halide perovskite materials reflects the charge dynamics inside of the material and thus contains important information for understanding the electro-optical properties of the material. Interpretation of PL blinking of methylammonium lead iodide (MAPbI3) nanostructures observed on polycrystalline samples remain...
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Optical antennas made of metallic nanostructures dramatically enhance single-molecule fluorescence to boost the detection sensitivity. Moreover, emission properties detected at the optical far field are dictated by the antenna. Here we study the emission from molecule-antenna hybrids by means of super-resolution localization and defocused imaging....
Article
Organometal halide perovskites show promising features for cost-effective application in photovoltaics. The material instability remains a major obstacle to broad application because of the poorly understood degradation pathways. Here, we apply simultaneous luminescence and electron microscopy on perovskites for the first time, allowing us to monit...
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Supported metal nanoparticle catalysts are commonly obtained through deposition of metal precursors onto the support using incipient wetness impregnation. Typically, empirical relations between metal nanoparticle structure and catalytic performance are inferred from ensemble averaged data in combination with high-resolution electron microscopy. Thi...