Construction of Cs2AgBiCl6/COF Heterojunction for Boosted Photocatalytic Thioester Oxidation.

Lead-free halide perovskites as a new kind of potential candidate for photocatalytic organic synthesis have attracted much attention recently. The rational heterojunction construction is regarded as an efficient strategy to delicately regulate their catalytic performances. Herein, a semi-conductive covalent organic framework (COF) nanosheet, C4N, is employed as the functional component to construct Cs2AgBiCl6/C4N (CABC/C4N) heterojunction. It is found that the C4N nanosheets with rich surface functional groups can serve as heterogeneous nucleation sites to manipulate the growth of CABC nanocrystals and afford close contact between each other, therefore facilitate the transfer and spatial separation of photogenerated charge carriers, as verified by in situ X-ray photoelectronic spectroscopy and Kelvin probe force microscopy. Moreover, the oxygen affinity of C4N endows the heterojunctions with outstanding aerobic reactivity, thus improving the photocatalytic performance largely. The optimal CABC/C4N heterojunction delivers a thioanisole conversion efficiency of 100% after 6 h, which is 2.2 and 7.7-fold of that of CABC and C4N. This work provides a new ideal for the design and application of lead-free perovskite heterojunction photocatalysts for organic reactions.

Full-color fiber light-emitting diodes based on perovskite quantum wires.

Fiber light-emitting diodes (Fi-LEDs), which can be used for wearable lighting and display devices, are one of the key components for fiber/textile electronics. However, there exist a number of impediments to overcome on device fabrication with fiber-like substrates, as well as on device encapsulations. Here, we uniformly grew all-inorganic perovskite quantum wire arrays by filling high-density alumina nanopores on the surface of Al fibers with a dip-coating process. With a two-step evaporation method to coat a surrounding transporting layer and semitransparent electrode, we successfully fabricated full-color Fi-LEDs with emission peaks at 625 nanometers (red), 512 nanometers (green), and 490 nanometers (sky-blue), respectively. Intriguingly, additional polydimethylsiloxane packaging helps instill the mechanical bendability, stretchability, and waterproof feature of Fi-LEDs. The plasticity of Al fiber also allows the one-dimensional architecture Fi-LED to be shaped and constructed for two-dimensional or even three-dimensional architectures, opening up a new vista for advanced lighting with unconventional formfactors.

Band Structure Optimized by Electron-Acceptor Cations for Sensitive Perovskite Single Crystal Self-Powered Photodetectors.

Low-dimensional perovskites afford improved stability against moisture, heat, and ionic migration. However, the low dimensionality typically results in a wide bandgap and strong electron-phonon coupling, which is undesirable for optoelectronic applications. Herein, semiconducting A-site organic cation engineering by electron-acceptor bipyridine (bpy) cations (2,2'-bpy2+ and 4,4'-bpy2+) is employed to optimize band structure in low-dimensional perovskites. Benefiting from the merits of lower lowest unoccupied molecular orbital (LUMO) energy for 4,4'-bpy2+ cation, the corresponding (4,4'-bpy)PbI4 is endowed with a smaller bandgap (1.44 eV) than the (CH3NH3)PbI3 (1.57 eV) benchmark. Encouragingly, an intramolecular type II band alignment formation between inorganic Pb-I octahedron anions and bpy2+ cations favors photogenerated electron-hole pairs separation. In addition, a shortening distance between inorganic Pb-I octahedral chains in (4,4'-bpy)PbI4 single crystal (SC) can effectively promote carrier transfer. As a result, a self-powered photodetector based on (4,4'-bpy)PbI4 SC exhibits 131 folds higher on/off ratio (3807) than the counterpart of (2,2'-bpy)2Pb3I10 SC (29). The presented result provides an effective strategy for exporting novel organic cation-based low-dimensional perovskite SC for high-performance optoelectronic devices.

High-efficiency, flexible and large-area red/green/blue all-inorganic metal halide perovskite quantum wires-based light-emitting diodes.

Metal halide perovskites have shown great promise as a potential candidate for next-generation solid state lighting and display technologies. However, a generic organic ligand-free and antisolvent-free solution method to fabricate highly efficient full-color perovskite light-emitting diodes has not been realized. Herein, by utilizing porous alumina membranes with ultra-small pore size as templates, we have successfully fabricated crystalline all-inorganic perovskite quantum wire arrays with ultrahigh density and excellent uniformity, using a generic organic ligand-free and anti-solvent-free solution method. The quantum confinement effect, in conjunction with the high light out-coupling efficiency, results in high photoluminescence quantum yield for blue, sky-blue, green and pure-red perovskite quantum wires arrays. Consequently, blue, sky-blue, green and pure-red LED devices with spectrally stable electroluminescence have been successfully fabricated, demonstrating external quantum efficiencies of 12.41%, 16.49%, 26.09% and 9.97%, respectively, after introducing a dual-functional small molecule, which serves as surface passivation and hole transporting layer, and a halide vacancy healing agent.

In Situ Loading of Cu Nanocrystals on CsCuCl3 for Selective Photoreduction of CO2 to CH4.

Rational design and facile synthesis of efficient environmentally friendly all-inorganic lead-free halide perovskite catalysts are of great significance in photocatalytic CO2 reduction. Aiming at photogenerated charge carrier separation and CO2 reaction dynamics, in this paper, a CsCuCl3 /Cu nanocrystals (NCs) heterojunction catalyst is designed and synthesized via a simple acid-etching solution process by using Cu2 O as the sacrificed template. Due to the disproportionation reaction of Cu2 O induced by concentrated hydrochloric acid, Cu NCs can be deposited onto the surface of CsCuCl3 microcrystals directly and tightly. As revealed by photoelectrochemical analysis, in situ Fourier transform infrared spectra, etc., the Cu NCs contribute a lot to extracting photoelectrons of CsCuCl3 to improve the charge separation efficiency, regulating the CO2 adsorption and activation, and also stabilizing the reaction intermediates. Therefore, CsCuCl3 /Cu heterojunction exhibits a total electron consumption rate of 58.77 µmol g-1 h-1 , which is 2.9-fold of that of single CsCuCl3 . Moreover, high CH4 selectivity of up to 92.7% is achieved, which is much higher than that of CsCuCl3 (50.4%) and most lead-free halide perovskite-based catalysts. This work provides an ingenious but simple strategy to rationally design cocatalysts in situ decorated perovskite catalysts for manipulating both the catalytic activity and the product selectivity.

Ultrasound-Assisted Crystallization Enables Large-Area Perovskite Quasi-Monocrystalline Film for High-Sensitive X-ray Detection and Imaging.

In recent years, halide perovskites have shown great application potential in X-ray detection due to their superior optoelectronic properties and high X-ray attenuation coefficient. However, large-area perovskite fabrication for high performance X-ray detectors remains extremely challenging. Herein, ultrasound-assisted crystallization combined with the hot-pressing method is proposed to prepare large-area (10 cm × 10 cm) and high-quality quasi-monocrystalline thick film of a mixed-cation perovskite MA0.42 FA0.58 PbI3 . The rapid ultrasound-assisted crystallization provides more homogeneous nucleation, which is essential to the fabrication of large-area and uniform perovskite microcrystalline film. Furthermore, the post hot-pressing treatment is implemented to fuse the crystal boundaries, rearrange the crystal grains, and eliminate the voids between crystals, resulting in a quasi-monocrystalline film. After the hot-pressing treatment, the carrier mobility and the carrier mobility-lifetime product increased about 13-fold (from 1.8 to 23.5 cm2 s-1 V-1 ) and 18 times (from 8.4 × 10-6 to 1.5 × 10-4 cm2 V-1 ), respectively. As a result, a high-performance MA0.42 FA0.58 PbI3 quasi-monocrystalline X-ray detector is achieved with an impressively high sensitivity (1.16 × 106 µC Gyair -1 cm-2 ) and low detection limit (37.4 nGyair s-1 ), demonstrating the potential of the ultrasound-assisted crystallization and hot-pressing strategy from an industrial perspective.

Constructing the Sulfur-Doped CdO@In2O3 Nanofibers Ternary Heterojunction for Efficient Photocatalytic Hydrogen Production.

An S-doped CdO@In2O3 nanofiber was successfully designed by in-situ electrospinning along and subsequent calcination treatment. Under artificial sunlight illumination, the S/CdO@In2O3-25 displayed a superior photocatalytic hydrogen evolution rate of 4564.58 µmol·g-1·h-1, with approximately 22.0 and 1261.0-fold of those shown by the S/CdO and S/In2O3 samples, respectively. The experimental and theoretical analyses illustrate that the unique one-dimensional (1D) nanofiber morphology and rich oxygen vacancies optimized the electronic structure of the nanofibers and adsorption/desorption behaviors of reaction intermediates, contributing to the realization of the remarkable solar-to-H2 conversion efficiencies. Moreover, the staggered band structure and intimate contact heterointerfaces facilitate the formation of a type-II double charge-transfer pathway, promoting the spatial separation of photoexcited charge carriers. These results could inform the design of other advanced catalyst materials for photocatalytic reactions.

A Melt-Quenched Luminescent Glass of an Organic-Inorganic Manganese Halide as a Large-Area Scintillator for Radiation Detection.

Glass is a group of materials with appealing qualities, including simplicity in fabrication, durability, and high transparency, and they play a crucial role in the optics field. In this paper, a new organic-inorganic metal halide luminescent glass exhibiting >78 % transmittance at 506-800 nm range together with a high photoluminescence quantum yield (PLQY) of 28.5 % is reported through a low-temperature melt-quenching approach of pre-synthesized (HTPP)2 MnBr4 (HTPP=hexyltriphenylphosphonium) single crystal. Temperature-dependent X-ray diffraction, polarizing microscopy, and molecular dynamics simulations were combined to investigate the glass-crystal interconversion process, revealing the disordered nature of the glassy state. Benefiting from the transparent nature, (HTPP)2 MnBr4 glass yields an outstanding spatial resolution of 10 lp mm-1 for X-ray imaging. The superb optical properties and facility of large-scale fabrication distinguish the organic-inorganic metal halide glass as a highly promising class of materials for optical devices.

Large-Area Laminar TEA2MnI4 Single-Crystal Scintillator for X-ray Imaging with Impressive High Resolution.

Current X-ray imaging scintillators are dominated by inorganic scintillators grown through a high-temperature process. Exploring new types of scintillators with mild growth conditions, high light yields, and eco-friendly chemical compositions is essential and challenging. Herein, the zero-dimensional large-area laminar organic-inorganic hybrid metal halide TEA2MnI4 (TEA = tetraethylammonium) single crystal with dimensions of 50 mm × 60 mm × 0.82 mm is grown via a local-heating solvent evaporation method. Compared with its Cl- and Br-based counterparts, the incorporation of the iodine component enhances the X-ray attenuation ability and significantly accelerates the decay of the photoluminescence of TEA2MnI4. Interestingly, the prepared TEA2MnI4 exhibits a high transmittance of >90% over the range of 515-765 nm and exhibits a high light yield of 26288 photons/MeV, which provides the prerequisite for high-resolution X-ray imaging. The TEA2MnI4 single-crystal scintillator displays an astonishing spatial resolution exceeding 25 line pairs per millimeter, which provides a design concept for a Mn-I-based single crystal for high-performance scintillator applications.

Inorganic Copper-Based Halide Perovskite for Efficient Photocatalytic CO2 Reduction.

In view of the toxicity of the Pb element, exploring eco-friendly Pb-free halide perovskites with excellent photoelectric properties is of great research and practical application significance. Herein, copper-based halide perovskite CsCuCl3 and the corresponding Br--substituted sample (CsCuCl2Br) are designed and explored as the catalysts for photocatalytic CO2 reduction for the first time. A facile antisolvent recrystallization process with pre-prepared single crystals as the precursor is employed to controllably synthesize CsCuCl3 and CsCuCl2Br microcrystals (MCs). The electronic structure and charge transfer property analysis by theoretical and experimental investigation reveal that CsCuCl3 possesses a satisfying bandgap (1.92 eV) and conduction band minimum (CBM) to harvest the sunlight and drive the conversion of CO2 to CH4 and CO. The Br- substitution can not only narrow the bandgap but also facilitate the transportation of charge carriers. Thus, a total electron consumption rate of 44.71 µmol g-1 h-1 is achieved for CsCuCl2Br MCs, which is much better than that of same-sized CsPbBr3 microcrystals or even better than many perovskite nanocrystal photocatalysts. This study suggests that Cu-based perovskites can serve as promising candidates for artificial photosynthesis or other photocatalytic applications, which may propose a new thought to construct lead-free, low-cost photocatalysts.

F-Type Pseudo-Halide Anions for High-Efficiency and Stable Wide-Band-Gap Inverted Perovskite Solar Cells with Fill Factor Exceeding 84.

The quality of wide-band-gap (WBG) perovskite films plays an important role in tandem solar cells. Therefore, it is necessary to improve the performance of WBG perovskite films for the development of tandem solar cells. Here, we employ F-type pseudo-halogen additives (PF6- or BF4-) into perovskite precursors. The perovskite films with F-type pseudo-halogen additives have a larger grain size and higher crystal quality with lower defect density. At the same time, the perovskite lattice increases due to substitution of F-type pseudo-halogen anions for I-/Br-, and the stress distortion in the film is released, which effectively suppresses the recombination of carriers, reduces the charge transfer loss, and inhibits the phase separation. Finally, the power conversion efficiency (PCE) of the inverted 1.67 eV perovskite devices is significantly improved to over 20% with an impressive fill factor of 84.02% and excellent device stability. In addition, the PCE of the four-terminal (4T) perovskite/silicon tandem solar cells reached 27.35% (PF6-) and 27.11% (BF4-), respectively. This provides important guidance for further improving WBG perovskite solar cell performance.

Zero-Dimensional Zn-Based Halides with Ultra-Long Room-Temperature Phosphorescence for Time-Resolved Anti-Counterfeiting.

Though fluorescence-tag-based anti-counterfeiting technology has distinguished itself with cost-effective features and huge information loading capacity, the clonable decryption process of spatial-resolved anti-counterfeiting cannot meet the requirements for high-security-level anti-counterfeiting. Herein, we demonstrate a spatial-time-dual-resolved anti-counterfeiting system based on new organic-inorganic hybrid halides BAPPZn2 (Cly Br1-y )8 (BAPP=1,4-bis(3-ammoniopropyl)piperazinium, y=0-1) with ultra-long room-temperature phosphorescence (RTP). Remarkably, the afterglow lifetime can be facilely tuned by regulating the halide-induced heavy-atom effect and can be identified by the naked eyes or with the help of a simple machine vision system. Therefore, the short-lived unicolor fluorescence and lasting-time-tunable RTP provide the prerequisites for unicolor-time-resolved anti-counterfeiting, which lowers the decryption-device requirements and further provides the design strategy of advanced portable anti-counterfeiting technology.

A-Site Diamine Cation Anchoring Enables Efficient Charge Transfer and Suppressed Ion Migration in Bi-Based Hybrid Perovskite Single Crystals.

Due to the large distance or weak electronic conjugation between adjacent Bi-I octahedrons, the charge transport in the low-dimensional bismuth-based hybrid perovskites is impeded and thus hinders their future developments. In this work, A-site cation engineering by monoamine BZA (benzylamine) and diamine 3-AMP (3-(aminomethyl)pyridine) has been demonstrated as an efficient strategy to regulate the corresponding activation energy of ionic migration and carrier transport capacity. Given the higher polarity of 3-AMP than BZA, producing a more efficient dielectric screening effect, it gives rise to obtaining the small exciton binding energy (50 meV) and low defect states (3.53×109  cm-3 ). The reduced distance of adjacent Bi-I octahedrons by the bilateral anchoring of the 3-AMP2+ diamine cation enhances both electronic conjugation and charge transport performance. Therefore, the photodetector for (3-AMP)BiI5 SC shows a 243-fold increase in on/off ratio compared with the (BZA)3 BiI6 SC.

Strongly Quantum-Confined Perovskite Nanowire Arrays for Color-Tunable Blue-Light-Emitting Diodes.

Color tunability of perovskite light-emitting diodes (PeLEDs) by mixed halide compositional engineering is one of the primary intriguing characteristics of PeLEDs. However, mixed halide PeLEDs are often susceptible to color red-shifting caused by halide ion segregation. In this work, strongly quantum-confined perovskite nanowires (QPNWs) made of CsPbBr3 are grown in nanoporous anodic alumina templates using a closed space sublimation process. By tuning the pore size with atomic layer deposition, QPNWs with a diameter of 6.6 to 2.8 nm have been successfully obtained, with continuous tunable photoluminescence emission color from green (512 nm) to pure blue (467 nm). To better understand the photophysics of QPNWs, carrier dynamics and the benefit of alumina passivation are studied and discussed in detail. Eventually, PeLEDs using various diameters of CsPbBr3 QPNWs are successfully fabricated with cyan color (492 nm) PeLEDs, achieving a record high 7.1% external quantum efficiency (EQE) for all CsPbBr3-based cyan color PeLEDs. Sky blue (481 nm) and pure blue (467 nm) PeLEDs have also been successfully demonstrated, respectively. The work here demonstrates a different approach to achieve quantum-confined one-dimensional perovskite structures and color-tunable PeLEDs, particularly blue PeLEDs.

Water-Molecule-Induced Emission Transformation of Zero-Dimension Antimony-Based Metal Halide.

Low-dimensional organic-inorganic metal halides have recently emerged as a class of promising luminescent materials. However, the intrinsic toxicity of lead would strongly hamper future application. Herein, we synthesized a new type of lead-free zero-dimensional (0D) antimony-based organic-inorganic metal halide single crystals, (PPZ)2SbCl7·5H2O (PPZ = 1-phenylpiperazine), which features a broadband emission at 720 nm. Ultrafast transient absorption and temperature-dependent photoluminescence (PL) spectra are combined to investigate the PL mechanism, revealing that self-trapped exciton recombination was involved. Furthermore, it is interesting that (PPZ)2SbCl7·5H2O material shows reversible PL emission transformation between red light (720 nm) and yellow light (590 nm) as water molecules are inserted or removed from the lattice. Such reversible emission transformation phenomenon renders the (PPZ)2SbCl7·5H2O as a potential low-cost water sensing material.

Indium-antimony-halide single crystals for high-efficiency white-light emission and anti-counterfeiting.

Although single-source white emissive perovskite has emerged as a class of encouraging light-emitting material, the synthesis of lead-free halide perovskite materials with high luminous efficiency is still challenging. Here, we report a series of zero-dimensional indium-antimony (In/Sb) alloyed halide single crystals, BAPPIn2-2x Sb2x Cl10 (BAPP = C10H28N4, x = 0 to 1), with tunable emission. In BAPPIn1.996Sb0.004Cl10, bright yellow emission with near 100% photoluminescence quantum yield (PLQY) is yielded when it was excited at 320 nm, which turns into bright white-light emission with a PLQY of 44.0% when excited at 365 nm. Combined spectroscopy and theoretical studies reveal that the BAPP4+-associated blue emission and inorganic polyhedron-afforded orange emission function as a perfect pair of complementary colors affording white light in BAPPIn1.996Sb0.004Cl10 Moreover, the interesting afterglow behavior, together with excitation-dependent emission property, makes BAPPIn2-2x Sb2x Cl10 as high-performance anti-counterfeiting/information storage materials.

Surface passivated halide perovskite single-crystal for efficient photoelectrochemical synthesis of dimethoxydihydrofuran.

Halide perovskite single-crystals have recently been widely highlighted to possess high light harvesting capability and superior charge transport behaviour, which further enable their attractive performance in photovoltaics. However, their application in photoelectrochemical cells has not yet been reported. Here, a methylammonium lead bromide MAPbBr3 single-crystal thin film is reported as a photoanode with potential application in photoelectrochemical organic synthesis, 2,5-dimethoxy-2,5-dihydrofuran. Depositing an ultrathin Al2O3 layer is found to effectively passivate perovskite surface defects. Thus, the nearly 5-fold increase in photoelectrochemical performance with the saturated current being increased from 1.2 to 5.5 mA cm-2 is mainly attributed to suppressed trap-assisted recombination for MAPbBr3 single-crystal thin film/Al2O3. In addition, Ti3+-species-rich titanium deposition has been introduced not only as a protective film but also as a catalytic layer to further advance performance and stability. As an encouraging result, the photoelectrochemical performance and stability of MAPbBr3 single-crystal thin film/Al2O3/Ti-based photoanode have been significantly improved for 6 h continuous dimethoxydihydrofuran evolution test with a high Faraday efficiency of 93%.

High-performance light-driven heterogeneous CO2 catalysis with near-unity selectivity on metal phosphides.

Akin to single-site homogeneous catalysis, a long sought-after goal is to achieve reaction site precision in heterogeneous catalysis for chemical control over patterns of activity, selectivity and stability. Herein, we report on metal phosphides as a class of material capable of realizing these attributes and unlock their potential in solar-driven CO2 hydrogenation. Selected as an archetype, Ni12P5 affords a structure based upon highly dispersed nickel nanoclusters integrated into a phosphorus lattice that harvest light intensely across the entire solar spectral range. Motivated by its panchromatic absorption and unique linearly bonded nickel-carbonyl-dominated reaction route, Ni12P5 is found to be a photothermal catalyst for the reverse water gas shift reaction, offering a CO production rate of 960 ± 12 mmol gcat-1 h-1, near 100% selectivity and long-term stability. Successful extension of this idea to Co2P analogs implies that metal phosphide materials are poised as a universal platform for high-rate and highly selective photothermal CO2 catalysis.

Tetraphenylbutadiene-Based Symmetric 3D Hole-Transporting Materials for Perovskite Solar Cells: A Trial Trade-off between Charge Mobility and Film Morphology.

Two three-dimensional symmetric tetraphenylbutadiene derivatives decorated with diphenylamine or triphenylamine fragments are first prepared for use as hole-transporting materials (HTMs) in perovskite solar cells (PSCs). The HTMs are acquired using straightforward synthetic methods and facile purification techniques. The thermal stability, photophysical properties, electrochemical behaviors, computational study, hole mobility, X-ray diffraction, hole transfer dynamics, hydrophobicity, surface morphology, and photovoltaic performances of the HTMs are discussed. The highest power conversion efficiency (PCE) of CJ-04-based cell is 13.75%, which is increased to 20.06% when CJ-03 is used as HTM, superior to the PCE of the cell based on 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) (18.90%). The preparation cost of CJ-03 accounts for merely 23.1% of the price of commercial spiro-OMeTAD, while the concentration of CJ-03 solution used in the device fabrication (60.0 mg mL-1) is lower compared with that of the spiro-OMeTAD solution (72.3 mg mL-1). These results corroborate that the screw-like HTMs with a highly distorted configuration are facilely available and promising candidates for PSCs. More importantly, a practical solution is proposed to achieve moderate charge mobility and good film-formation ability of the HTMs simultaneously.

Coordination disk-type nano-Saturn complexes.

The first coordination disk-type nano-Saturn complexes, [Cu10(Mim)10]⊃C60 and [Cu10(Mim)10]⊃C70 (Mim = 2-methylimidazolate), were assembled under one-pot solvothermal conditions. The highest number of 30 C-Hπ interactions between the [Cu10(Mim)10] disk and the C60/C70 surfaces drives the formation of the nano-Saturns. The calculated interaction energy is much larger than that of most of the reported disk-type nano-Saturns. Different photoinduced charge/energy transfer mechanisms are present for both nano-Saturn systems to quench the intrinsic luminescence of the [Cu10(Mim)10] disk.