One-dimensional Crystal Structure Research Articles

Environmentally stable one-dimensional copper halide based ultra-flexible composite film for low-cost X-ray imaging screens

Environmentally stable, low cost, large stokes shift, adjustable area and flexibility are basic factors to prepare scintillator films for their commercial application. Here, a low cost (∼3 $/g) room-temperature ligand-assisted reprecipitation method is used to synthesize one-dimensional crystal structure based on Rb2CuX3 (X = Br, Cl). Rb2CuBr3 exhibits quite high mass yield of 90% with high Photoluminescence quantum yield (PLQY) of 59.06%. Importantly, its bright blue emission (90 nm stokes shift) is consistent with the highest optical detection efficiency wavelength range of commercial SiPM. Further characterizations point out that such effective blue emission comes from the recombination of excitons rather than the defects or combination of electron-hole pairs. And the existing strong exciton-photon coupling is conducive to the formation of self-trapped excitons (STEs). Finally, uniform and adjustable area Rb2CuBr3-polystyrene composite films have been successfully obtained. It's fascinating that the films exhibit ultra-flexibility (unchanged performance after multiple bending of 400 times) and excellent stability (subtle attenuation after 30 days of storage in a harsh environment). As an X-ray imaging screen, it presents a sensitive scintillation response to X-ray signals with superior linearity with high-quality images. Therefore, our prepared Rb2CuBr3 scintillator shows great commercial prospects in the field of flexible X-ray detection.

Magnetic Properties of the Hexagonal Ferromagnet NdCrGe3 Showing Metamagnetic Transition and Negative Magnetocaloric Effect

Single crystals of a hexagonal ferromagnet NdCrGe3 with one-dimensional crystal structure are synthesized, and the magnetic properties are comprehensively investigated, exhibiting large magnetic anisotropy and complex magnetic structure. Besides the ferromagnetic transition at TC = 101 K, we observe a sharp decrease in magnetization at T = 55 K and another two phase transitions at T = 31 and 15 K. These phase transitions imply complex and anisotropic magnetic structure in NdCrGe3. Below T = 55 K, metamagnetic transitions and negative magnetocaloric effects are detected under H//ab. Additionally, the critical properties around TC = 101 K and the anisotropic magnetocaloric effect are investigated in detail.

Superconductivity in Nb2Pd3Te5 and Chemically-Doped Ta2Pd3Te5

We report on the superconductivity in ternary transition metal tellurides Ta2Pd3Te5 and Nb2Pd3Te5, which have a one-dimensional crystal structure. Single-crystalline and polycrystalline samples of Ta2Pd3Te5 show nonmetallic electron conduction, while Ti or W doping results in metallic behavior with a bulk superconducting transition at 2-4 K. In contrast, the polycrystalline samples of Nb2Pd3Te5, which are found to be isostructural to Ta2Pd3Te5, show a bulk superconducting transition at 3.3 K. The crystal structure and physical properties of Ta2Pd3Te5 and Nb2Pd3Te5 are also discussed in comparison with a candidate excitonic insulator Ta2NiSe5.

Revealing composition and structure dependent deep-level defect in antimony trisulfide photovoltaics

Antimony trisulfide (Sb2S3) is a kind of emerging light-harvesting material with excellent stability and abundant elemental storage. Due to the quasi-one-dimensional symmetry, theoretical investigations have pointed out that there exist complicated defect properties. However, there is no experimental verification on the defect property. Here, we conduct optical deep-level transient spectroscopy to investigate defect properties in Sb2S3 and show that there are maximum three kinds of deep-level defects observed, depending on the composition of Sb2S3. We also find that the Sb-interstitial (Sbi) defect does not show critical influence on the carrier lifetime, indicating the high tolerance of the one-dimensional crystal structure where the space of (Sb4S6)n ribbons is able to accommodate impurities to certain extent. This study provides basic understanding on the defect properties of quasi-one-dimensional materials and a guidance for the efficiency improvement of Sb2S3 solar cells.

One-dimensional Sb2Se3 enabling ultra-flexible solar cells and mini-modules for IoT applications

Power supply equipment, employed in the Internet of Things (IoT) for instance, calls for efficient harvesting of solar energy from the environment sustainably. Sb 2 Se 3 enjoys the advantages of unique one-dimensional crystal structure and low-temperature film growth, enabling the fabrication of flexible and lightweight solar cells. Therefore, Sb 2 Se 3 solar cells are expected to have intrinsic advantages in powering IoT sensors. Herein, the device configuration and film fabrication of flexible Sb 2 Se 3 solar cell was optimized and an efficiency up to 6.13% and power-per-weight of 2.04 W g -1 were obtained, both of which are the highest records for flexible Sb 2 Se 3 solar cells. Benefitting from the intrinsically high flexibility of Sb 2 Se 3 and the thin flexible substrate, our device retained 96% of its initial performance after 1000-times bending at the extremely small curvature radius of 0.5 mm. Furthermore, the first Sb 2 Se 3 mini-module (25 cm 2 area) was constructed and its application in powering a blue LED under all weather conditions and a flower monitor (IoT sensors) was demonstrated. This work opens an avenue toward flexible Sb 2 Se 3 solar cells and points out its future research direction. Solar cells, with high energy density and reliability, can serve as the power source for the sensors of the Internet of Things (IoT) sensor. Combining the intrinsically high flexibility of Sb 2 Se 3 and careful analysis of stain distribution, lightweight and ultra-flexible Sb 2 Se 3 solar cells and mini-modules were obtained and successfully applied to IoT sensors as energy supply. • The analysis of material mechanics and stain distribution guide the design of ultra-flexible Sb 2 Se 3 solar cells. • The flexible Sb 2 Se 3 solar cells exhibit high efficiency of 6.13%, high power-per-weight of 2.04 W g -1 . • The flexible Sb 2 Se 3 solar cells keep 96% of the initial PCE after 1000-times bending at a curvature radius of 0.5 mm. • The large-area (~ 25 cm 2 ) flexible Sb 2 Se 3 solar mini-modules are successfully applied for power supply of IoT sensors.

Stable and efficient Sb2Se3 solar cells with solution-processed NiOx hole-transport layer

Sb2Se3 is a promising absorber material for thin-film solar cells owing to its earth-abundant and non-toxic constituents, superior optoelectronic properties, and unique one-dimensional crystal structure. To further increase the power conversion efficiency of the Sb2Se3, we fabricated an n-i-p structure by integrating a solution-processed NiOx hole-transport layer (HTL) into Sb2Se3 solar cells to enhance the carrier collection. In this study, we systematically screen the thickness of NiOx HTL and demonstrate an improved average power conversion efficiency from 6.12% to 7.15% with a 50 nm NiOx HTL. The mechanism associated with the improved device performance was characterized through the microstructure of the material, device physics, and interface electronic behaviors. It is also shown that the low-cost and scalable solution-processed NiOx HTL can improve device stability under an accelerated stress test. Thus, this work paves a way to further improve the performance of antimony chalcogenides-based solar cells via tailoring the inorganic HTL.

Phase transition dynamics in one-dimensional halide perovskite crystals

Triiodide perovskites $${\rm CsPbI}_{3}$$ , $${\rm CsSnI}_{3}$$ , and $${\rm FAPbI}_{3}$$ (where FA is formamidinium) are highly promising materials for a range of optoelectronic applications in energy conversion. However, they are thermodynamically unstable at room temperature, preferring to form low-temperature (low-T) non-perovskite phases with one-dimensional anisotropic crystal structures. While such thermodynamic behavior represents a major obstacle toward realizing high-performance devices based on their high-temperature (high-T) perovskite phases, the underlying phase transition dynamics are still not well understood. Here we use in situ optical micro-spectroscopy to quantitatively study the transition from the low-T to high-T phases in individual $${\rm CsSnI}_{3}$$ and $${\rm FAPbI}_{3}$$ nanowires. We reveal a large blueshift in the photoluminescence (PL) peak (~38 meV) at the low-T/high-T two-phase interface of partially transitioned $${\rm FAPbI}_{3}$$ wire, which may result from the lattice distortion at the phase boundary. Compared to the experimentally derived activation energy of CsSnI3 (~1.93 eV), the activation energy of $${\rm FAPbI}_{3}$$ is relatively small (~0.84 eV), indicating a lower kinetic energy barrier when transitioning from a face-sharing octahedral configuration to a corner-sharing one. Further, the phase propagation rate in CsSnI3 is observed to be relatively high, which may be attributed to a high concentration of Sn vacancies. Our results could not only facilitate a deeper understanding of phase transition dynamics in halide perovskites with anisotropic crystal structures, but also enable controllable manipulation of optoelectronic properties via local phase engineering. Metal halide perovskites are a new class of semiconductors with great promise for a variety of optoelectronic applications. Owing to their soft ionic lattice, halide perovskites often exhibit rich phase transitions between different crystal structures, frequently from the “active” perovskite phases to undesirable “inactive” non-perovskite phases. Understanding and controlling this transition is vital for developing stable, high-performance devices. However, there is limited understanding on how different symmetry, crystal structure, and defect would impact such a phase transition process. In this report, in situ optical micro-spectroscopy is used to systematically investigate the phase transitions from non-perovskite to perovskite phases in individual CsSnI3 and FAPbI3 wires. Compared to the transition from an edge-sharing octahedral non-perovskite structure to a corner-sharing perovskite structure in CsSnI3, the activation energy for the FAPbI3 phase transition is relatively small, indicating a lower energy barrier when starting from a face-sharing octahedral structure in FAPbI3. The high concentration of Sn vacancies is probably responsible for the much higher phase propagation rate in CsSnI3 when compared to a CsPbBrxI3-x system with the same crystal structure but different halide vacancies. Our experimental results expand the knowledge of phase transition in halide perovskites and offer important guidance toward rationally designing more stable and efficient perovskite devices.

One-dimensional ZnSe/ZnS/BK7 ternary planar photonic crystals as wide angle infrared reflectors

In this work, we propose novel structures of one-dimensional ternary planar photonic crystals (1D-TPPC) consisting of periodic unit cells of dispersive materials. The transfer matrix method (TMM) is utilized to investigate the propagation of the electromagnetic radiation in the proposed structure. The transmittance spectrum and Floquet-Bloch theorem are used to determine the features of the photonic band gap (PBG) for the transverse electric (TE) mode of the incident radiation. In particular, the photonic band gap width (PBGW) is studied as a function of the number of unit cells, thicknesses of layers, angle of the incidence and temperature. Based on the results obtained, the proposed structures are believed to be promising in designing wide angle infrared reflectors.

Oriented-Structured CsCu2I3 Film by Close-Space Sublimation and Nanoscale Seed Screening for High-Resolution X-ray Imaging.

An all-inorganic lead-free halides Cs-Cu-I system, represented by Cs3Cu2I5 and CsCu2I3, has attracted attention for their good photophysical characteristics recently. Successive works had reported their application potential in light-emitting devices. However, there is no report for CsCu2I3 in X-ray scintillation detectors so far. We notice that CsCu2I3 may be advantageous in such an application due to the one-dimensional crystal structure, the congruent-melting feature, and the high spectral matching to some photosensors. In this work, we explore the scintillation properties and imaging application of CsCu2I3 in X-ray scintillator detector. The oriented structure is designed to enhance the imaging performance of a CsCu2I3 detector. Close-space sublimation process and nanoscale seed screening strategy are employed to realize this design by producing a large-area (25 cm2) CsCu2I3 thick film layer with the oriented nanorod structure. This CsCu2I3 detector eventually achieves a high spatial resolution of 7.5 lp mm-1 in X-ray imaging.

Parallel ultrafine SiO2 nanowires coated with amorphous SiO2

The parallel ultrafine SiO2 nanowires coated with amorphous SiO2 have been synthesized by a thermal evaporation method. The samples have been systematically studied by X-ray powder diffraction, Raman spectroscopy, scanning electron microscope, high-resolution transmission electron microscopy, selective area electron diffraction, and photoluminescence. The results show that the synthesized nanowire consists of a composite structure of the amorphous shell and the nanometer-sized crystalline core which has a monoclinic structure. The diameter of the internal one-dimensional crystal structure is about 10 nm. Furthermore, the luminous performance of SiO2 nanowires coated with amorphous SiO2 reveals a stable and strong yellow-red emission band. The products might be suitable for optoelectronic semiconductor application.

Room temperature synthesis of low-dimensional rubidium copper halide colloidal nanocrystals with near unity photoluminescence quantum yield.

Metal lead halide perovskite nanocrystals have emerged as promising candidates for optoelectronic applications. However, the inclusion of toxic lead is a major concern for the commercial viability of these materials. Herein, we introduce a new family of non-toxic reduced dimension Rb2CuX3 (X = Br, Cl) colloidal nanocrystals with one-dimensional crystal structure consisting [CuX4]3- ribbons isolated by Rb+ cations. These nanocrystals were synthesised using a room-temperature method under ambient conditions, which makes them cost effective and scalable. Phase purity quantification was confirmed by Rietveld refinement of powder X-ray diffraction and corroborated by 87Rb MAS NMR technique. Both samples also exhibited high thermal stability up to 500 °C, which is essential for optoelectronic applications. Rb2CuBr3 and Rb2CuCl3 display PL emission peaks at 387 nm and 400 nm with high PLQYs of ∼100% and ∼49%, respectively. Lastly, the first colloidal synthesis of quantum-confined rubidium copper halide-based nanocrystals opens up a new avenue to exploit their optical properties in lighting technology as well as water sterilisation and air purification.

Phase transition dynamics in one-dimensional halide perovskite crystals

Abstract

Design and analysis of omnidirectional solar spectrum reflector using one-dimensional photonic crystal

A one-dimensional photon crystal structure is proposed to design an omnidirectional broadband reflector. The structural parameters are optimized to reflect complete solar spectrum (0.3 to 2.3 μm) for both TE and TM polarized light. The design analysis is carried out using transfer matrix method. The structure is designed using alternate dielectric–dielectric layers of appropriate refractive indices and layer thicknesses. The proposed structure demonstrates more than 98% reflectivity for the complete wavelength range from 0.3 to 2.3 μm along with 73% emission in 8 to 13 μm, thus showing its potential as a dielectric-based reflector in applications such as daytime passive radiative coolers, and as a heliostat in concentrated solar power.

High-pressure synthesis, structure and properties of new ternary pnictides La3TiX5 (X = P, As)

Abstract The new ternary pnictides La3TiX5 (X = P, As) and the solid solutions of La3Ti(Sb1-xAsx)5 (x = 0–1) and La3Ti(As1-yPy)5 (y = 0–1) were synthesized under high pressure and high temperature conditions. The crystal structure of La3TiX5 (X = P, As) was determined from the X-ray powder diffraction data. These compounds crystallize in a hexagonal Hf5Sn3Cu-anti type structure with the space group P63/mcm and lattice parameters a = 8.7927 A and c = 5.7643 A for La3TiP5, and a = 9.0267 A and c = 5.9071 A for La3TiAs5, in which the face-sharing TiX6 octahedral chains running along the c axis are separated by La3+ in the interstice sites with a distance about 9 A, presenting a strong one-dimensional crystal structure. Physical properties measurements indicate La3TiX5 (X = P, As) are Pauli paramagnetic metals. The calculations reveal that La3+ ions are not perfectly ionic owing to the non-negligible contributions of La to the density of state (DOS) at the Fermi level and bridge the X atoms between the chains, which make the samples to be 3-dimensional metals. What’s more, the change of X in La3TiX5 from Sb to P increases the ionicity of La3+ and thus decreases the electron hopping between the conducting chains.

Design of multipeak one-way light absorber based on one-dimensional magnetophotonic crystal

The study of magnetophotonic crystals is usually based on its reflection and transmission of light waves, but its absorption properties are rarely studied. Considering the current high absorptivity of one-way absorbers has one absorption peak, and the optical constants of magnetophotonic crystals are all ideal approximation, we introduce the practical optical constants of silicon carbide (SiC) into the magnetophotonic crystals model. The optical properties are investigated in visible wavelength based on the transformation matrix method, and some parameter effects are also discussed in detail, such as the incidence angle and the thickness of defect layer. The one-dimensional (1-D) magnetophotonic crystal structure was systematically optimized. Then a multipeak one-way light absorber composed of real semiconductor and metal based on 1-D magnetophotonic crystal is further proposed, which makes the channel position of perfect nonreciprocal absorption controllable and the number increased; the influence of incident conditions on the absorption efficiency is greatly weakened and the universality and flexibility of one-way absorber in practice are greatly enhanced. The achievement provides new ideas for the study of nonreciprocal absorbers.

Enhanced absorptivity based on nonreciprocal effect of CdTe and excitation of surface polaritons

In this work, the purpose of increasing the magneto-optical conversion rate is achieved by enhancing the electromagnetic field in the magnetic medium, thereby forcing the magneto-optical effect of the system by the excitation of magnetic or surface polaritons, which requires constructing a magneto-plasmon micro/nanoscale structure reasonably. Considering the current high absorptivity of non-reciprocal absorbers are almost at very small wavelengths, therefore, an one-dimensional periodic magnetic plasma crystal structure composed of gold film and diluted magnetic semiconductor was constructed for broading the absorption range, and the absorption efficiency and nonreciprocal effect were investigated based on the finite difference time domain method. Moreover, the geometrical parameters of crystal structure was systematically optimized due to the balance between magneto-optic effect and optical properties can be obtained by adjusting the geometric parameters of the structures, and high absorptivity and relative obvious nonreciprocal effect in mid-infrared band had been obtained. From the results, it can be showed that the emergence of absorptance resonance peaks and troughs mainly depends on the excitation of surface plasmon resonance and the symmetry of micro-cavity effect in grating grooves. The achievement in this work provides new ideas for the study of nonreciprocal optical properties.

Effects of post-deposition annealing and copper inclusion in superstrate Sb2Se3 based solar cells by thermal evaporation

Earth-abundancy, nontoxic constituent, along with excellent stability and optoelectronic properties make antimony selenide (Sb2Se3) one of the potential candidate for low cost photovoltaics. In this work, antimony selenide (Sb2Se3) thin films were prepared by low temperature thermal evaporation method and characterized. Solar cells were fabricated in the superstrate configuration of Glass/ITO/ZnO/CdS/Sb2Se3/Au. It was found that annealing in vacuum after Sb2Se3 deposition played a significant role in the device performance. One-dimensional crystal structure of Sb2Se3 with a preferred grain orientation was found to be beneficial for the higher performance of the solar cells with vacuum annealing at 300 °C. Furthermore, Cu addition after the deposition of Sb2Se3 was introduced to improve the back contact and the device performance. In particular, Cu addition as a back contact leads to a significant increase in the Voc and the fill factor (FF). Moreover, aging of the finished cells during accelerated stability tests revealed a light soaking effect without degradation even in case of copper insertion. Our best solar cell showed a conversion efficiency of 3.5% without selenization.

(Invited) High-Performance 2D Tellurium Transistors Towards CMOS Logic Applications

The thirst for novel two-dimensional (2D) materials for ultra-scaled electronics keeps growing during the last decade as the downsizing trend of silicon-based conventional semiconductors is approaching its physical limit. An ideal paradigm of 2D materials suitable for logic device applications should possess high carrier mobility for both type of carriers, good air-stability, controllable doping scheme and a reasonable bandgap. Recently reported hydrothermal growth technique of 2D tellurium (Te) thin films, which meet all the above criteria, offers a new option for 2D material-based CMOS applications. Tellurium is a narrow bandgap p-type semiconductor (0.35 eV) with nearly symmetric mobilities for both electrons and holes of around 700 cm2/Vs at room temperature. It has one-dimensional chiral crystal structure and can be grown into 2D films under right conditions. Just like other 2D materials, these 2D facets of Te also contain no dangling bonds and therefore the 2D films can preserve the material properties and have great potential for miniaturizing device geometry in principle. Here we first report systematic investigation of 2D Te p-type transistor performance approaching atomic-thin limit. The device key parameters, such as field-effect mobility, on/off ratio and stability were thoroughly studied as a function of film thickness. The device performance was then optimized through contact and dielectric engineering, and large drive current over 1 A/mm was achieved. We further employed photo-current mapping method to show that rare accumulation-type ohmic contacts were formed using high work function metal (palladium). Finally, we present an atomic layer deposited (ALD) dielectric doping technique to effectively dope the intrinsically p-type channel into n-type with almost symmetric operations for both NMOS and PMOS. Prototypical inverters based on Te CMOS demonstrate great potential of constructing Te-based high-speed CMOS logic circuits. Our work not only established a comprehensive guideline for designing and optimizing 2D Te based CMOS devices, but also provided a device platform to explore versatility of 2D Te from many other perspectives, such as condensed matter physics and thermoelectronics.

Copper(I)-Based Highly Emissive All-Inorganic Rare-Earth Halide Clusters

Summary The development of new environmentally friendly luminescent materials is crucial for future solid-state lighting, sensor, and display applications. Here, a Cu(I)-based all-inorganic rare-earth halide material, Rb 8 CuSc 3 Cl 18 , has been synthesized by a solid-state reaction method. In this compound, two Cu(I) ions are connected to three rare-earth halide octahedra to form a paddle-wheel-like cluster. The Cu(I) coordinated rare-earth halide clusters contribute to a strong blue photoluminescence emission. This Cu(I)-regulated emission can be extended to other isostructural compounds, such as Rb 8 CuY 3 Cl 18 . Moreover, the crucial role of Cu(I) has been illustrated by the isostructural non-emissive Rb 8 AgSc 3 Cl 18 . On the basis of comprehensive spectroscopy studies and density functional theory calculations, we found that Cu(I) photo-oxidation and correct orbital-energy-level alignment are crucial for the observed bright-blue emission through a proposed metal (Cu)-to-octahedra ([ScCl 6 ] 3− ) charge-transfer mechanism. The discovery of Cu(I)-based all-inorganic rare-earth halide clusters establishes a new strategy for constructing promising emissive halide materials.

9.2%-efficient core-shell structured antimony selenide nanorod array solar cells

Antimony selenide (Sb2Se3) has a one-dimensional (1D) crystal structure comprising of covalently bonded (Sb4Se6)n ribbons stacking together through van der Waals force. This special structure results in anisotropic optical and electrical properties. Currently, the photovoltaic device performance is dominated by the grain orientation in the Sb2Se3 thin film absorbers. Effective approaches to enhance the carrier collection and overall power-conversion efficiency are urgently required. Here, we report the construction of Sb2Se3 solar cells with high-quality Sb2Se3 nanorod arrays absorber along the [001] direction, which is beneficial for sun-light absorption and charge carrier extraction. An efficiency of 9.2%, which is the highest value reported so far for this type of solar cells, is achieved by junction interface engineering. Our cell design provides an approach to further improve the efficiency of Sb2Se3-based solar cells.