- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Defining the composition and electronic structure of large-scale and single-crystalline like Cs2AgBiBr6 films fabricated by capillary-assisted dip-coating method
摘要： Owning the merits of both lead-free and air-stable, the double-perovskite Cs2AgBiBr6 has attracted increasing attention, but suffers low visible-light absorption coefficient due to its large indirect bandgap. Moreover, the electronic structure of its synthesized films has not been explored clearly yet. In this work, we developed a general and promising method to fabricate continuous, uniform and highly orientated Cs2AgBiBr6 films in large scale on various substrates through capillary-assisted dip-coating method. Strikingly, those optimized films are single crystalline verified by 4-scan XRD. Its electronic structure was carefully studied independently by multi-photo-physical characterizations. Its bandgap can be tuned from 2.65 to 2.25 eV by changing the substrate temperature in growth from 40 to 160 °C. Essentially, their work-function (WF) was determined at ~5.01 eV and WF-VBM is around 2 eV. This novel band structure with typical n-type characteristic, was further confirmed by DFT calculations, which reveals that the Cs interstitials and Br vacancies derived deep defect levels were fixed around its Fermi level, closer to the conduction band. This conclusion is different from its widely accepted p-type feature, but definitely deepens our understanding of this material and inspires us to find more valuable strategies of modulating its band structure and optoelectronic properties.
关键词： Single-crystalline perovskite films
更新于2025-11-20 15:33:11
-
Beta-lead oxide quantum dot (β-PbO QD)/polystyrene (PS) composite films and their applications in ultrafast photonics
摘要： Polymer composite films, particularly those based on polymers and layered nanomaterials, are attractive materials for exploiting the properties of multiple materials for applications in electronics and photonics. In this work, a beta-lead oxide quantum dot (β-PbO QD)/polystyrene (PS) composite film is successfully fabricated by a solution blending method. The β-PbO QDs are well-distributed within a β-PbO QD/PS composite film and the composite film is transparent and flexible. Owing to the almost complete insolubility of both β-PbO QDs and PS, the as-fabricated β-PbO QD/PS composite film holds the nonlinear photonic response from 540 nm to 1060 nm under complete water immersion, confirming its excellent stability to high humidity. Additionally, the β-PbO QD/PS composite film exhibits a considerable capacity for optical modulation owing to a strong nonlinear absorption coefficient compared with those of other two-dimensional (2D) materials. On the basis of a home-made β-PbO QD/PS composite film saturable absorber, stable mode-locked pulses at 1060 nm are generated under humid conditions. It is anticipated that the β-PbO QD/PS composite films enable the exploitation of new waterproof, flexible photonic devices based on functional 2D materials and polymers.
关键词： composite films,mode-locked pulses,ultrafast photonics,polystyrene,nonlinear absorption,beta-lead oxide quantum dot
更新于2025-11-19 16:56:42
-
Enhancing photoluminescence of carbon quantum dots doped PVA films with randomly dispersed silica microspheres
摘要： As a kind of excellent photoluminescent material, carbon quantum dots have been extensively studied in many fields, including biomedical applications and optoelectronic devices. They have been dispersed in polymer matrices to form luminescent films which can be used in LEDs, displays, sensors, etc. Owing to the total internal reflection at the flat polymer/air interfaces, a significant portion of the emitted light are trapped and dissipated. In this paper, we fabricate free standing flexible PVA films with photoluminescent carbon quantum dots embedded in them. We disperse silica microspheres at the film surfaces to couple out the total internal reflection. The effects of sphere densities and diameters on the enhancement of photoluminescence are experimentally investigated with a homemade microscope. The enhancement of fluorescence intensity is as high as 1.83 when the film is fully covered by spheres of 0.86 μm diameter. It is worth noting that the light extraction originates from rather the scattering of individual spheres than the diffraction of ordered arrays. The mechanism of scattering is confirmed by numerical simulations. The simulated results show that the evanescent wave at the flat PVA/air interface can be effectively scattered out of the film.
关键词： silica microspheres,light extraction,photoluminescence,PVA films,carbon quantum dots
更新于2025-11-19 16:46:39
-
Effect of Deposition Potential on Synthesis, Structural, Morphological and Photoconductivity Response of Cu2O Thin Films by Electrodeposition Technique
摘要： The present work describes the effect of deposition potentials on structural, morphological, optical, electrical and photoconductivity responses of cuprous oxide (Cu2O) thin films deposited on fluorine-doped tin oxide glass substrate by employing electrodeposition technique. X-ray diffraction patterns reveal that the deposited films have a cubic structure grown along the preferential (111) growth orientation and crystallinity of the film deposited at ? 0.4 V is improved compared to the films deposited at ? 0.2, ? 0.3 and ? 0.5 V. Scanning electron microscopy displays that surface morphology of Cu2O film has a well-defined three-sided pyramid-shaped grains which are uniformly distributed over the surface of the substrates and are significantly changed as a function of deposition potential. Raman and photoluminescence spectra manifest that the film deposited at ? 0.4 V has a good crystal quality with higher acceptor concentration compared to other films. UV–visible analysis illustrates that the absorption of Cu2O thin film deposited at ? 0.4 V is notably higher compared to other films and the band gap of Cu2O thin films decreases from 2.1 to 2.04 eV with an increase in deposition potential from ? 0.2 to ? 0.5 V. The frequency–temperature dependence of impedance analysis shows that the film deposited at ? 0.4 V has a high conductivity. I–V measurements elucidate that the film deposited at ? 0.4 V exhibits a good photoconductivity response compared to films deposited in other deposition potentials.
关键词： Cu2O thin films,Electrodeposition,I–V measurement,Photoconductivity response
更新于2025-11-19 16:46:39
-
Origin of Ferroelectricity in Epitaxial Si-doped HfO2 Films
摘要： HfO2-based unconventional ferroelectric (FE) materials were recently discovered and have attracted a great deal of attention in both academia and industry. The growth of epitaxial Si-doped HfO2 films has opened up a route to understand the mechanism of ferroelectricity. Here, we used pulsed laser deposition (PLD) to grow epitaxial Si-doped HfO2 films in different orientations of N-type SrTiO3 substrates. Using piezoforce microscopy, polar nanodomains can be written and read, and these domains are reversibly switched with a phase change of 180o. Films with different thicknesses displayed a coercive field Ec and a remnant polarization Pr of approximately 4～5 MV/cm and 8～32 μC/cm2, respectively. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) results identified that the as-grown Si-doped HfO2 films have strained fluorite structures. The ABAB stacking mode of the Hf atomic grid observed by HRTEM clearly demonstrates that the ferroelectricity originates from the noncentrosymmetric Pca21 polar structure. Combined with soft X-ray absorption spectra (XAS), it was found that the Pca21 ferroelectric crystal structure manifested as O sublattice distortion by the effect of interface strain and Si dopant interactions, resulting in further crystal-field splitting as a nanoscaled ferroelectric ordered state.
关键词： HRTEM,PLD,XRD,Ferroelectricity,PFM,XAS,Epitaxial Si-doped HfO2 thin films,N-type SrTiO3 substrates
更新于2025-11-14 17:04:02
-
Interface modified flexible printed conductive films via Ag <sub/>2</sub> O nanoparticle decorated Ag flake inks
摘要： A new approach to stable, low resistance inexpensive printed flexible conductive inks is proposed. Silver inks have been extensively studied and commercialized for applications in printed electronics due to the inherent high conductivity and stability of silver, even in particulate-based percolation networks processed at temperatures compatible with low cost polymer films such as polyethylene terephthalate (PET). Recent interest in flexible and even stretchable circuits, however, has presented new challenges for particle-based inks as mechanical strains can result in the opening of critical particle-to-particle contacts. Here we report a facile, low cost method for the single step synthesis of stable, printable nanoscale Ag2O-decorated Ag flake inks which can be converted to highly conductive Ag films at 150°C curing temperature without the use of limited shelf life organometallics or low metal loading nanoparticles to modify the interface between silver flakes. Analysis indicate that decoration of Ag flakes with Ag2O nanoparticles (NPs) during ink synthesis improves the conductivity and flexibility of printed silver films by forming bridging interconnections between Ag flakes after low temperature reduction of the Ag2O NPs. In this work, printed nano-decorated silver conductors with starting oxide to metal weight ratios of 5:95 exhibited lateral resistivities lower than 1.5×10-5 ? cm, which was 35% less than films derived from undecorated Ag flake inks of the same total Ag loading and binder system. This resistivity difference increased to 45% after cyclic bend testing showing increased resilience to repeated flexing for the nano-decorated inks. Through detailed compositional and morphological characterizations, we demonstrate that such improved conductivity and flexibility is due to a more effective bridging afforded by the in-situ synthesized Ag NPs on the surface of Ag flakes. These properties, combined with the simplified syntheses method of the nano-ink, make the material a viable, advantageous alternative to the limited number of stretchable conductors currently available.
关键词： Ag2O nanoparticle-decorated Ag flake inks,printed conductive films,interface modification,silver ink
更新于2025-11-14 17:04:02
-
Electrochromic Properties of Nanostructured WO <sub/>3</sub> Thin Films Deposited by Glancing‐Angle Magnetron Sputtering
摘要： Tungsten oxide thin films are prepared by glancing-angle reactive magnetron sputtering at room temperature. The surface and cross-section morphologies are characterized by FE-SEM and TEM. The electrochromic properties of the thin films are studied using a three-electrode system in 1 m LiClO4/PC solution. When the glancing angle is kept at 80°, a nanocolumnar structured film is obtained. This nanocolumnar structured film shows a lower driving potential and better stability compared to the dense film. The charge capacity per unit area of the nanocolumnar structured film is determined to be 30.85 mc cm?2. The diffusion rates of injection and detachment of ions are determined to be Din = 6.57 × 10?10 cm2 s?1 and Dde = 6.55 × 10?10 cm2 s?1 under an applied potential of ±1.2 V, respectively. The optical modulation amplitude of the nanocolumnar structured film reaches 65% at a wavelength of 600 nm and the optical density is superior to that of the dense film.
关键词： nanostructured,electrochromic,WO3 thin films,glancing angle,magnetron sputtering
更新于2025-11-14 17:03:37
-
Direct Hot-Injection Synthesis of Lead Halide Perovskite Nanocubes in Acrylic Monomers for Ultrastable and Bright Nanocrystal–Polymer Composite Films
摘要： In recent years, lead halide perovskite nanocrystals (NCs) have attracted significant attention in both fundamental research and commercial applications due to their excellent optical and optoelectrical properties. However, the protective ligands on the surface of the perovskites NCs could be easily removed after the tedious process of centrifugation, separation, and dispersion, which greatly hampers their stability against light, heat, moisture, and oxygen and limits their practical applications. Here we report a new post-processing-free strategy (i.e., without centrifugation, separation, and dispersion process) of using an UV-polymerizable acrylic monomer of lauryl methacrylate (LMA) as the solvent to synthesize CsPbBr3 NCs, and then adding polyester polyurethane acrylates oligomer, monomer (IBOA) and initiator for directly UV polymerization to fabricate NC-polymer composite films. These films exhibited an improved photoluminescence quantum yield (85-90%) than classic NC-film (40-50%), which were processed using octadecene (ODE) as the solvent for NC synthesis and post-processed for UV polymerization. Significantly, the as-fabricated films by post-processing-free strategy exhibited excellent photostability against strong Xe lamp illumination; while the other films using classic methods were quickly photo-degraded. Meanwhile, these NC-polymer composite films showed good stability against moisture and heating when aging in water at 50oC for over 200 hours. These films, along with K2SiF6:Mn4+ (KSF) phosphor emitters, were used as downconverters for blue LEDs in liquid crystal displays with a wide color gamut of 115% in the International Commission on Illumination (CIE) 1931 color space. This work provides a facile and effective strategy for the preparation of ultrastable and bright color-conversion NC films for the development of the next-generation wide color gamut displays.
关键词： display backlight,lead halide perovskite,colloidal nanocrystals,color-conversion optical films,photostability
更新于2025-11-14 17:03:37
-
A flexible surface-enhanced Raman substrates based on cellulose photonic crystal/Ag-nanoparticles composite
摘要： Surface-enhanced Raman scattering (SERS) significantly increases Raman scattering intensity. SERS usually uses rough-surface nano-metal materials such as gold, silver and copper as a substrate [1]. It has been widely used in surface science, analytical science and other fields [2-4]. According to the preparation method, SERS substrates can be divided into three categories: (1) solid phase substrates with fixed metal nanoparticles [5, 6]; (2) metal nanostructures prepared by nanoimprinting [7, 8]; (3) metal nanostructures prepared by template method [9-11]. Conventional SERS substrates, such as roughened surfaces of noble metals, are difficult to control and the SERS effect is unstable due to the random distribution of nanostructures. The microstructure of the nanometer regular pattern, which is processed by etching and electron beam deposition, is limited by the high cost of the instrument, the complicated production process, the difficulty to make large area and the subsequent modification of the surface. The SERS substrate prepared by a template of nanospheres array has a good controllability and reproducibility. By assembling nanospheres with different sizes to prepare the templates of different thicknesses, 2D metal films with different spacing can be obtained. The preparation of SERS substrate based on nanospheres array is simple and has low cost, easy regulation and high reproducibility. Protective agent and surfactant are not required in the preparation, meanwhile, the obtained substrate is relatively pure. PhCs are periodic structures which can be generated by a controllable self-assembly method of the spherical colloidal particles [12-15]. Light propagated inside PhCs follows Bragg's law of diffraction [16-19]. The characteristics of PhCs strongly depend on the spatial structure. Because of its cost-efficiency and easy preparation, PhC has attracted significant attentions in the application of optical sensors, optical switches [20, 21] and display devices [22-26]. The regular periodical structures can also be used as template to prepare other structural functional materials [27]. A lot of researches on the preparation and application of PhCs have been carried out in our recent work [28, 29]. Based on the special capture effect of PhC optical bandgap, the plasma effect of silver nanoparticles and the enrichment of cellulose matrix on analytes in organic solvents, we designed a combination of three properties for enhancing Raman scattering. Design concept is as follows: a PhC array which bandgap matches the incident light is used as a template, filled with a cellulose matrix that is easily degraded, and modified with silver nanoparticles. Based on the above design, a novel surface-enhanced Raman scattering substrate made by Ag-nanoparticles modified flexible cellulose photonic crystal film was firstly prepared. We synthesized an Ag-nanoparticles modified PhCs methylcellulose film (Ag-PHC-MCF) and carboxymethyl cellulose film (Ag-PHC-CMCF) SERS flexible substrates using the PhCs as templates. The innovative combination of metal nanoparticles and the ordered PhCs cellulose film (PHCCF) effectively avoided the aggregation of metal nanoparticles, as a result, the hot spots of the metal nanoparticles were distributed around the pores to ensure the uniform adsorption of the target analytes and uniform Raman signals on a large area. Through the excellent enrichment of cellulose film with pore structures, the targets in the organic solvent were captured on the cellulose film, so the Raman detection signals of the analyte were enhanced with the contact probability between the targets and the hot spots of metal nanoparticles increasing. At the same time, the light scattered on the PHCCF was enhanced significantly because of the trapping effect of PhC. Based on the original combination of the enrichment of porous methylcellulose, the plasmon resonance of Ag and the bandgap of photonic crystal, the composite film has a significant enhancement of the Raman signals. Simultaneously, due to its good degradability, it also has outstanding advantages in environmental protection. Meanwhile, it is easy to be carried and preserved because of its flexibility and light texture, which has great superiorities in transportation and storage.Therefore, it is of great significance in industrial pollutant detection or national defense safety monitoring.
关键词： SERS,cellulose films,photonic crystal,plasmonic responses
更新于2025-11-14 15:27:09
-
Solubilization of Carbon Nanotubes with Ethylene-Vinyl Acetate for Solution-Processed Conductive Films and Charge Extraction Layers in Perovskite Solar Cells
摘要： Carbon nanotube (CNT) solubilization via non-covalent wrapping of conjugated semiconducting polymers is a common technique used to produce stable dispersions for depositing CNTs from solution. Here, we report the use of a non-conjugated insulating polymer, ethylene vinyl acetate (EVA), to disperse multi- and single-walled CNTs (MWCNT and SWCNT) in organic solvents. We demonstrate that despite the insulating nature of the EVA, we can produce semitransparent films with conductivities of up to 34 S/cm. We show, using photoluminescence spectroscopy, that the EVA strongly binds to individual CNTs, thus making them soluble, preventing aggregation, and facilitating the deposition of high-quality films. To prove the good electronic properties of this composite, we have fabricated perovskite solar cells using EVA/SWCNTs and EVA/MWCNTs as selective hole contact, obtaining power conversion efficiencies of up to 17.1%, demonstrating that the insulating polymer does not prevent the charge transfer from the active material to the CNTs.
关键词： perovskite solar cells,carbon nanotubes,insulating polymer,conductive films,CNT polymer functionalization
更新于2025-11-14 15:25:21