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Hydrophobic Metal Halide Perovskites for Visible-Light Photoredox C-C Bond Cleavage and Dehydrogenation Catalysis
摘要： Two-dimensional lead and tin halide perovskites were prepared by intercalating the long alkyl group 1-hexadecylammonium (HDA) between the inorganic layers. We observed visible-light absorption, narrow-band photoluminescence, and nanosecond photoexcited lifetimes in these perovskites. Due to their hydrophobicity and stability even in humid air, we applied these perovskites in the decarboxylation and dehydrogenation of indoline acids using (HDA)2PbI4 or (HDA)2SnI4 as photoredox catalysts, with quantitative conversions and high yields for the former. We highlight another original application of the metal halide perovskites.
关键词： photocatalysis,2D metal halide perovskites,decarboxylation,photooxidation,hydrophobic perovskite
更新于2025-09-23 15:23:52
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Impedance Spectroscopy: A Versatile Technique to Understand Solution-Processed Optoelectronic Devices
摘要： Solution-processed optoelectronic devices based on conjugated polymers, colloidal quantum dots (CQDs), halide perovskites, and so on are now emerging as a new-generation semiconductor technology which prevails its conventional counterparts in terms of low fabrication cost, ease of scalable manufacturing, and abundant material designability. However, the solution-processed thin films obtained through spin-coating, spray, inkjet printing, and doctor blading usually suffer from low film quality and a high defect density especially at the interfaces of different functional layers. Currently, the most significant subject is to address the non-ideal interfaces for achieving improved performance of the devices. Impedance spectroscopy (IS) is a universal technique that can help to examine the charge behavior at the interfaces in an electrochemical or solid-state multilayered device. Owing to its ability to elucidate the charge transfer, charge transport, and accumulation within the interfaces of electrochemical or multilayered devices with minimal effects to the devices themselves, the use of IS has increased vividly in the last decades. This review provides the basic principles of IS and its applications on solution-processed optoelectronic devices.
关键词： optoelectronic devices,metal halide perovskites,quantum dots,impedance spectroscopy,solution processing
更新于2025-09-23 15:22:29
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Hydrophobic Metal Halide Perovskites for Visible-Light Photoredox C-C Bond Cleavage and Dehydrogenation Catalysis
摘要： Two-dimensional lead and tin halide perovskites were prepared by intercalating the long alkyl group 1-hexadecylammonium (HDA) between the inorganic layers. We observed visible-light absorption, narrow-band photoluminescence, and nanosecond photoexcited lifetimes in these perovskites. Due to their hydrophobicity and stability even in humid air, we applied these perovskites in the decarboxylation and dehydrogenation of indoline acids using (HDA)2PbI4 or (HDA)2SnI4 as photoredox catalysts, with quantitative conversions and high yields for the former. We highlight another original application of the metal halide perovskites.
关键词： photocatalysis,2D metal halide perovskites,decarboxylation,photooxidation,hydrophobic perovskite
更新于2025-09-23 15:22:29
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Mechanisms of LiF Interlayer Enhancements of Perovskite Light-Emitting Diodes
摘要： The use of LiF as a thin interlayer between the electron transport layer and cathode has played a pivotal role in remarkable advances in perovskite LEDs (PeLEDs); however, the mechanism behind the effect of LiF remains to be fully understood. Here we report a combined experimental and computational study from which we ascribe the benefits of a LiF interlayer to the migration of dissociated Li into the cathode and dissociated F into the anode. Electronic device simulations reveal that the former improves electron injection by lowering the Schottky barrier height, while the latter reduces the barrier width. These reduce turn-on voltage and improve current density and charge balance in LEDs. We fabricate PeLEDs with and without the LiF interlayer and link these materials and electronic phenomena to the device light-current-voltage characteristics. X-ray photoelectron spectroscopy obtained in sputter profiling of PeLEDs corroborates the dissociation of LiF.
关键词： LEDs,interface dipoles,metal-halide perovskites,photoelectron spectroscopy,band alignment
更新于2025-09-23 15:21:01
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Dual-site mixed layer-structured FA <sub/>x</sub> Cs <sub/>3a??x</sub> Sb <sub/>2</sub> I <sub/>6</sub> Cl <sub/>3</sub> Pb-free metal halide perovskite solar cells
摘要： Structure engineering of trivalent metal halide perovskites (MHPs) such as A3Sb2X9 (A ? a monovalent cation such as methyl ammonium (MA), cesium (Cs), and formamidinium (FA) and X ? a halogen such as I, Br, and Cl) is of great interest because a two dimensional (2D) layer structure with direct bandgap has narrower bandgap energy than a zero dimensional (0D) dimer structure with indirect bandgap. Here, we demonstrated 2D layer structured FACs2Sb2I6Cl3 MHP by dual-site (A and X site) mixing. Thanks to the lattice-symmetry change by I–Cl mixed halide, the shortest ionic radius of Cs, and the lower solution energy due to dual-site mixing, the FACs2Sb2I6Cl3 MHP had 2D layer structure and thereby the MHP solar cells exhibited improved short-circuit current density.
关键词： metal halide perovskites,2D layer structure,bandgap engineering,dual-site mixing,solar cells
更新于2025-09-23 15:21:01
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Integrating Properties Modification in the Synthesis of Metal Halide Perovskites
摘要： Metal halide perovskites have attracted enormous attention and show huge potential as promising building blocks of next-generation optoelectronic devices owing to their unique optical and electrical properties. For further promoting their practical applications in various fields, the synthesis of metal halide perovskites with desired characteristics is essential to satisfy the requirements of their applications. The properties of perovskites are highly related to their crystal structures and chemical compositions. The optoelectronic properties of perovskites can be altered via decreasing their dimensionality owing to the quantum confinement effect, while enlarging the crystal size of perovskite can promote the construction of device arrays with homogenous performance. In addition, modifying the chemical composition of perovskites via alloying, doping, or controlling vacancies also greatly changes their optical and electrical properties. Thus, integrating the properties modification in the synthesis process of metal halide perovskites can not only improve the productivity of the desired perovskites but also provide a great opportunity to prepare designed crystals with predictable features. The exciting progress in the synthesis of metal halide perovskites with controllably tailored properties is summarized herein. It is hoped that these technologies can promote the development of perovskites.
关键词： properties modification,metal halide perovskites,synthesis integrating
更新于2025-09-23 15:21:01
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Aira??Stable Highly Crystalline Formamidinium Perovskite 1D Structures for Ultrasensitive Photodetectors
摘要： State-of-the-art optoelectronic devices based on metal-halide perovskites demand solution-processed structures with high crystallinity, controlled crystallographic orientation, and enhanced environmental stability. Formamidinium lead iodide (α-FAPbI3) possesses a suitable bandgap of 1.48 eV and enhanced thermal stability, whereas perovskite-type polymorph (α-phase) is thermodynamically instable at ambient temperatures. Stable α-FAPbI3 perovskite 1D structure arrays with high crystallinity and ordered crystallographic orientation are developed by controlled nucleation and growth in capillary bridges. By surface functionalization with phenylethylammonium ions (PEA+), FAPbI3 wires sustain a stable α-phase after 28 day storage in the ambient environment with a relative humidity of 50%. Enhanced photoluminescence (PL) intensity and elongated PL lifetime demonstrate suppressed trap density and high crystallinity in these 1D structures, which is also reflected by the enhanced diffraction density and pure (001) crystallographic orientation in the grazing-incidence wide-angle X-ray scattering (GIWAXS) pattern. Based on these high-quality 1D structures, sensitive photodetectors are achieved with average responsivities of 5282 A W?1, average specific detectivities of more than 1.45 × 1014 Jones, and a fast response speed with a 3 dB bandwidth of 15 kHz.
关键词： metal-halide perovskites,1D structures,photodetectors,α-FAPbI3
更新于2025-09-23 15:19:57
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A Study of Eu Doping in Nanolayers of CsPbBr <sub/>3</sub> using Ab Initio Calculations to Understand <i>fa??f</i> Transitions in Eu <sup>3+</sup> -Doped Nanocrystals for Light-Emitting Diodes
摘要： Recent experiments on Eu doped nanocrystals of CsPbX3 (X = Cl, Br) show that Eu exists in 3+ oxidation state even though it substitutes Pb which is in 2+ state in these perovskites. Therefore, the question arises, what is it that leads to the formation of Eu3+ in nanocrystals of these materials? In order to understand this, we have studied the doping of Eu in a slab (~1.8 nm thick) of CsPbBr3 from ab initio calculations and explored various possibilities that could lead to the formation of Eu3+ and the occurrence of f-f transitions. These include: 1) the presence of a Cs vacancy, 2) the existence of H or OH due to moisture, 3) substitution of O at a surface halogen site, and 4) the possibility of excess halogen around Eu. It is found that the presence of surface oxygen is the most likely reason for the observation of Eu3+ in these nanolayers. Our results show the presence of partially occupied spin-up f states and 6.48 μB magnetic moment on Eu that could lead to the possibility of f-f transition in these doped systems. A similar result has also been obtained for Eu doped in CsPbCl3 nanolayers. The calculated change in energy when defects/impurities are present gives favourable indication of finding H, OH, and Br as interstitials and O as substitutional entities, but Cs vacancy is unlikely. Additionally, we find that the doping of Eu in nanolayers does not affect the atomic structure and the cost of doping is also very small making these perovskites very promising materials for light emitting diodes and other solid-state lighting applications.
关键词： Two-dimensional systems,Light emitting diodes,Solid state lighting,Density functional theory,Metal-halide perovskites,Nanolayers,Defects,f-f transitions
更新于2025-09-23 15:19:57
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Solution-processed one-dimensional CsCu <sub/>2</sub> I <sub/>3</sub> nanowires for polarization-sensitive and flexible ultraviolet photodetectors
摘要： Polarization-sensitive ultraviolet (UV) photodetectors are highly desired due to their great significance in many applications. As the newly-emerging functional semiconductors, the metal-halide perovskites have attracted huge attention in photodetection due to their excellent optoelectronic features. However, the ever-reported perovskites polarized photodetectors mainly focused on the visible/infrared-light region, and the devices targeted at the UV region have not been reported. Here, for the first time, ternary copper halides CsCu2I3 nanowire was used as the light absorber to achieve polarization-sensitive UV photodetection. By combining the intrinsic anisotropy of the asymmetry structure and external morphology anisotropy of CsCu2I3 nanowires, a record photocurrent anisotropy ratio of ~3.16 was achieved, and also the shortcomings of lead-toxicity and environmental instability for conventional lead-halide perovskites were overcome effectively. Moreover, such photodetectors fabricated on flexible substrate demonstrate good flexibility and stability, showing almost no photoresponse degradation after extremely bending for 1000 cycles. The results suggest that the lead-free CsCu2I3 nanowire is potentially an attractive candidate for high-performance polarization-sensitive UV photodetectors compatible for practical applications.
关键词： CsCu2I3 nanowires,Polarization-sensitive,metal-halide perovskites,lead-free,ultraviolet photodetectors,flexible substrate
更新于2025-09-19 17:13:59
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High-performance blue perovskite light-emitting diodes based on the a??far-field plasmonic effecta?? of gold nanoparticles
摘要： Metal halide perovskites have become the next-generation electroluminescent materials due to their excellent optoelectronic properties. In the last several years, there has been tremendous progress in the performance of red and green-light perovskite electroluminescent devices (PeLEDs) with external quantum efficiencies (EQE) exceeding 14% and 21%, respectively. In contrast, blue PeLEDs are still in infancy stage, due to EQEs below 1%. Therefore, development of blue PeLEDs is sorely needed since blue light plays a vital role in achieving full-color and white-light emission. In order to improve the efficiency of blue PeLEDs, herein we introduce gold nanoparticles (Au NPs) into poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layer (HTL) to achieve a high performance blue PeLEDs with an emission wavelength ~475 nm. By introducing Au NPs, the optical properties of poly(ethylene oxide) (PEO):PEA2(CsPbBrxCl3?x)n?1PbBr4 perovskite films have been significantly improved leading to 3.8 times enhancement in fluorescence intensity. Based on this improvement, the blue PeLEDs record a maximum luminance and EQE of ~1110 cd/m2 and 1.64%, respectively performing among the best reported so far. Finally, the PeLED performance improvement is attributed to the far-field surface plasmonic effect of Au NPs. This effect is originated from the interference between the original chromophores emission and the mirror-reflected emission of mirror-type substrates. This study not only reveals the function of Au NPs in development of blue PeLEDs, but also offers new insights into the fundamental physics underlying the effect of surface plasmon resonance of Au NPs on perovskite light emitting devices.
关键词： gold nanoparticles,blue PeLEDs,Metal halide perovskites,far-field plasmonic effect,external quantum efficiency
更新于2025-09-19 17:13:59