Visible Light Range Research Articles

Optimizing novel perovskite Mg3AsBr3 through uniaxial stress: a comprehensive study of its potential in solar and optoelectronic applications

This study presents a detailed investigation into optimizing the novel perovskite Mg3AsBr3 through uniaxial stress for enhanced performance in solar and optoelectronic applications. Using Density Functional Theory (DFT), we examined its structural, electronic, and optical properties under uniaxial stress from 0.5 to 5.0 GPa. Key findings include the tuning of the material’s bandgap from 1.485 eV (without stress) to an optimized range closer to 1.13581 eV under 5.0 GPa, demonstrating potential for improved solar cell efficiency. Our findings reveal a nuanced response of the material’s absorption coefficients at critical energies of 2.92 eV and 4.0 eV, where a descending trend with increasing pressure was observed, indicating a plateau at 1.5 GPa and an anomalous increase at 2.5 GPa. This behavior underscores the significance of stress between 2.5 GPa to 5.0 GPa in tailoring the optical responses essential for enhancing solar absorption efficiency in the ultraviolet to visible light range (300–800 nm). Notably, the dielectric constant increased gradually with stress, peaking at 6.003 under 0.5 GPa and slightly diminishing at 5.0 GPa, suggesting enhanced polarization and intrinsic response to electric fields under mechanical stress. Our research highlights the potential of stress engineering in optimizing perovskite materials for renewable energy applications, offering a pathway to high-efficiency, low-cost solar cells.

Preventive conservation of paper-based relics with visible light high-transmittance ultraviolet blocking film based on carbon dots

Paper-based relics is an important carrier for recording and preserving information, however, it faces irreversible UV-induced damage, including photocleavage, oxidation, acidification and discoloration, which seriously affects its value and lifespan. Carbon dots (CDs) possess excellent UV absorption and good chemical stability, making them suitable for UV protection. Herein, we propose a high-security and efficient method utilizing CDs films (CDFs) for preventive protection of paper against UV damage. The CDFs with high tunable UV absorbance and minimal absorbance in the visible light range, effectively shield paper from UV radiation while preserving its visual appeal. Moreover, the UV transmittance of the film can be fine-tuned to the content of CDs and can be easily removed from the paper without residue. Artificial accelerated UV aging experiments demonstrate the deceleration of acidification, oxidation, and photocleavage in the protected bamboo paper and Xuan paper. This research paces a new direction for the protection of paper and paper-based relics and artworks with emerging carbon materials, offering customizable protection effects tailored to specific preservation and exhibition requirements. This research pioneers a novel approach to preventive protection of paper and paper-based relics using emerging carbon dots materials, offering tailored protection for diverse preservation needs.

Design and modification thienonaphthalimides based non-fullerene acceptors for organic solar cells with high photovoltaic performance in visible light absorption range

Herein, we theoretically designed and characterized eight new thienonaphthalimides-based non-fullerene acceptor (NFA) materials (MT1–MT8) derived from 1ad molecule for organic solar cells (OSCs) devices. In this study, density functional theory (DFT) and time-dependent density functional theory were used to perform theoretical characters of all molecules. All computational analysis were successfully done at mPW1PW91/6-31g(d,p) DFT level. Compared with R (3.25 eV), MT4 showed better planarity and narrower band gap of 2.470 eV. A relatively lower excitation energy (2.039 eV) and binding energy (0.431 eV) were also found in MT4. Meanwhile, molecular electrostatic potential, transition density matrix and hole-electron analyses proved that MT4 had better photovoltaic and photophysical properties than R. We also designed J52-Cl:MT4 blend compound to study the charge transfer behavior at the interface which shown successful shift of electrons from donor to acceptor. Therefore, our newly designed molecules have the potential of being good NFAs for efficient OSC devices.

A multiscale dilated attention network for hyperspectral image classification

Hyperspectral imaging is an image obtained by combining spectral detection technology and imaging technology, which can collect electromagnetic spectra in the wavelength range of visible light to near-infrared. It is an important research content in the field of ground observation in hyperspectral remote sensing. However, hyperspectral image face significant challenges in classification task due to their high spectral dimensions, lack of labeled samples, and strong correlation between bands. In order to fully extract features from both spectral and spatial dimensions and improve classification accuracy in the case of limited training samples, a multiscale dilated attention network is proposed for hyperspectral image classification. First, a three-dimensional convolutional layer is used to extract the shallow features of the image. Then, a multiscale dilated attention module is proposed by combining dilated convolution and channel attention. Using ordinary convolution and dilated convolution to form different receptive fields. Channel attention is used to remodel the obtained multiscale features, enhancing the inter-channel correlation. After that, a multiscale spatial-spectral attention module is constructed using multiple asymmetric convolutions to obtain spatial and spectral attention features at different positions, further enhancing important feature suppression over non-important features. Finally, using softmax to classify the obtained features. Using Indian Pines, Pavia University, KSC and University of Houston as experimental datasets, the overall classification accuracy of this paper’s method achieved 98.97%, 99.14%, 99.45%, and 98.56% respectively, using only 5%, 1%, 10%, and 10% of training samples per class. Compared with seven advanced classification methods, the experimental results show that the proposed method can achieve the highest classification accuracy with limited training samples.

Study on the modulation of luminescence peak position and luminescence mechanism of black phosphorus

The application of black phosphorus in optoelectronic devices is hindered because of its inherent band gap characteristics. In the paper, black phosphorus was prepared by high-energy ball milling, and its related structure and properties were characterized. At the same time, the luminescence mechanism of black phosphorus was explored, and the effect of ultrasonic time on the structure and optical properties of black phosphorus was studied. The luminescence peak of black phosphorus can be modulated to the visible light range after adding polyethylene glycol, and the luminescence of black phosphorus is closely related to the P (020) and P (021). It was found that the luminescence intensity of alcoholized black phosphorus decreases with the increase of ultrasonic time. When the ultrasonic time is 15min, the luminescence intensity of alcoholized black phosphorus decreases greatly, this is because that the content of P (020) in black phosphorus decreases with the increase of ultrasonic time, resulting in the decrease of luminescence intensity.

Highly stable, low voltage, flexible photodetector in UV-visible region from self-assembled organic small molecule

The fabrication of a high-performance, low voltage operated flexible organic photodetector (OPD) based on solution self-assembled crystalline thin film of a small molecule, viz, 6,13 bis(tri-isopropylsilylethynyl) pentacene (Tips pentacene) is reported. The OPD demonstrated excellent photodetection ability under range of visible light as well as under UV light, with low illumination intensity. Under 590 nm illumination (5.6 µW/cm2), the device showcased photo to dark current ratio (Iphoto/Idark), ca. 25, photoresponsivity (P) of 89 mA/W, detectivity of 1.81×1010 jones at 1 V bias and response times of 0.04/0.2 sec. Photocurrent modulation of the OPD has been realized by varying the channel width, incident wavelength, applied bias and the illumination intensity. The OPD exhibited excellent photodetection ability under different tensile bending, with roughly 55 % decline in Iphoto/Idark value and 30 % decline in R value under bending radius of 7.5 mm. The OPD could withstand thousands of repeated bending/folding cycles, and regain its initial photoresponse characteristics, if put at rest for 2 hours. The excellent device performances with its precise tuning via various input stimuli suggests that present OPD have great potential for future low cost, low energy and wearable optoelectronics.

A novel hydrogen-bonded organic framework/g-C3N4 heterojunction for improved sulfadiazine photodegradation via effective electron transfer

As one of the most widely used antibiotics, sulfamethoxazole (SDZ) poses significant health risks to the ecological environment by causing harm to aquatic organisms and accelerating evolution of antibiotic resistant bacteria. Metalloporphyrin hydrogen-bonded organic framework (PFC-72) demonstrates promising prospect in the field of photocatalysis owing to its high specific surface area, wide light harvesting range, stable physical and chemical properties, and semiconductor properties. Herein, we constructed an efficient photocatalyst PFC-72/g-C3N4 by one-step solvent thermal method for photocatalytic degradation of SDZ. When doping content of PFC-72 is 10 %, photocatalytic degradation efficiency of SDZ can reach 96.82 % after 120 min of visible light irradiation, and PFC-72/g-C3N4 exhibits excellent structural stability. The photocatalytic efficiency of SDZ is improved by increasing specific surface area, enhancing absorption range of visible light, and inhibiting recombination of photogenerated electron-hole pairs. In addition, photodegradation pathways of SDZ in PFC-72/g-C3N4 was determined by UPLC-MS/MS analysis. Finally, dominant reactive species (·O2−, hVB+, and ·OH) in the system were detected through free radical masking experiments, and photocatalytic mechanism was clarified. This work investigates a novel and efficient porphyrin-HOF based photocatalyst, which has great potential for degradation of SDZ.

Ferroelectric, flexoelectric and photothermal coupling in PVDF-based composites for flexible photoelectric sensors.

A ferroelectric polyvinylidene fluoride (PVDF) film with excellent flexibility possesses great potential for photodetection and wearable devices. However, the relatively weak photo-absorption and the consequent small photocurrent limit its photofunctional properties. Herein, we embedded a strongly visible-light active material system, 0.5Ba(Zr0.08Ti0.8Mn0.12)O3-0.5(Ba0.7Ca0.3)TiO3 (BZTM-BCT) loaded with Ag and Au nanoparticles, into a PVDF film, which demonstrates a significantly higher photovoltaic response in the whole visible light range with a β-phase content of over 90%. In a state of "bending + poling", the PVDF/BZTM-BCT:Au film presents an optimal response for photoelectric properties by exhibiting a photocurrent that is 57 times higher than that of a pure PVDF film when illuminated with 405 nm LED light at 100 mW cm-2. Photoexcitation and thermal excitation jointly contribute to the generation of free carriers, while the flexoelectric and ferroelectric coupling electric field provides a greater driving force for carrier separation and transport. More interestingly, composite film-based photoelectric sensors can simultaneously respond to light and the movement and deformation of contacted things, indicating its potential in versatile applications. Overall, this work puts forward a new route for designing new flexible multifunctional photoelectric devices.

Novel MoS2-In2O3-WS2 (2D/3D/2D) ternary heterostructure nanocomposite material: Efficient photocatalytic degradation of antimicrobial agents under visible-light

Fabrication of ternary composited photocatalytic nanomaterials with strong interaction is vital to deriving the fast charge separation for efficient photodegradation of organic contaminants in wastewater under visible light. In this work, novel ternary 2D/3D/2D MoS2-In2O3-WS2 multi-nanostructures were synthesized using facile hydrothermal processes. XRD, FTIR, and XPS results confirmed the phase, functional groups, and element composition of pure MoS2, MoS2-In2O3, and MoS2-In2O3-WS2 hybrids. UV-DRS spectra of the MoS2-In2O3-WS2 ternary hybrid indicate maximum absorption in the visible light range with a band-gap energy value of 2.4 eV. The surface of the 2D WS2 nanosheet structure tightly blends and densely disperses 2D MoS2 nanosheets and 3D In2O3 nanocubes. This confirmed the formation of the MoS2-In2O3-WS2 ternary hybrid in the form of 2D/3D/2D multi-nanostructures, which is also indicated from SEM and HR-TEM images. The synthesized MoS2-In2O3-WS2 ternary hybrid showed maximum photocatalytic activity under visible-light for antimicrobial agents such as triclosan (TCS) and trichlorocarban (TCC). The photocatalytic activity of TCS was revealed to be 95% at 90 min, while that of TCC was 93% at 100 min. The reusability and stability tests of the prepared MoS2-In2O3-WS2 ternary hybrid after four consecutive photocatalytic cycles were analyzed by FTIR and SEM, which indicated that the prepared ternary hybrid was very stable. Overall results suggested that the developed MoS2-In2O3-WS2 (2D/3D/2D) multi-nanostructures are environmentally friendly and low-cost nanocomposites as a potential photocatalyst for the removal of antimicrobial agents from wastewater.

5CB-doped polymer-stabilised sphere-phase liquid crystal smart window with fast response and high transmittance

ABSTRACT Smart windows have become increasingly popular due to their ability to provide privacy protection, energy efficiency, and user control. Therefore, this technology has a wide range of applications in various fields such as construction, automotive, aviation, and renewable energy. However, commercialisation faces two significant challenges due to the slow response speed and low transmittance. This work demonstrates a 5CB-doped polymer-stabilised sphere-phase liquid crystal (PS-SPLC) smart window with sub-millisecond response time, which can be switched between transparent and scattering states by an electric field. The transmittance exceeds 90% when the voltage is on in the visible light range. This 5CB-doped PS-SPLC smart window has the potential to usher in a new era of smart window research.

A 1 × 8 Optical Splitter Based on Polycarbonate Multicore Polymer Optical Fibers.

Visible light communication (VLC) is becoming more relevant due to the accelerated advancement of optical fibers. Polymer optical fiber (POF) technology appears to be a solution to the growing demand for improved transmission efficiency and high-speed data rates in the visible light range. However, the VLC system requires efficient splitters with low power losses to expand the optical energy capability and boost system performance. To solve this issue, we propose an effective 1 × 8 optical splitter based on multicore polycarbonate (PC) POF technology suitable for functioning in the green-light spectrum at a 530 nm wavelength. The new design is based on replacing 23 air-hole layers with PC layers over the fiber length, while each PC layer length is suitable for the light coupling of the operating wavelength, which allows us to set the right size of each PC layer between the closer PC cores. To achieve the best result, the key geometrical parameters were optimized through RSoft Photonics CAD suite software that utilized the beam propagation method (BPM) and analysis using MATLAB script codes for finding the tolerance ranges that can support device fabrication. The results show that after a light propagation of 2 mm, an equally green light at a 530 nm wavelength is divided into eight channels with very low power losses of 0.18 dB. Additionally, the splitter demonstrates a large bandwidth of 25 nm and stability with a tolerance range of ±8 nm around the operated wavelength, ensuring robust performance even under laser drift conditions. Furthermore, the splitter can function with 80% and above of the input signal power around the operated wavelength, indicating high efficiency. Therefore, the proposed device has a great potential to boost sensing detection applications, such as Raman spectroscopic and bioengineering applications, using the green light.

Photoelectric properties of metallic elements doping and adsorption on graphene/black phosphene heterojunction

The electronic, optical properties and work function of Ti, Mg, Be doping and adsorption on G/BP heterojunction are investigated. The Eb of G/BP doping and adsorption with Ti, Mg and Be are analyzed. The special properties of single-layer material are preserved in G/BP and band gap is opened with 50 meV. Ti, Mg and Be doping and adsorption on G/BP exhibit metallic properties and doping atoms form impurity levels near Fermi level. Except for Ti-G system, Ti doping and adsorption systems exhibit strong ferromagnetic metallicity. Doping atoms Ti, Mg, and Be all lose electrons, while G/BP gains electrons. The doping and adsorption systems have electrostatic potential difference, indicating the formation of internal electric field from BP layer to G layer. Work function of G/BP is 4.481 eV, that of Ti, Mg, and Be adsorption on G/BP decrease compared to G/BP, indicating that Ti, Mg, and Be adsorption can improve conductivity of system. The research of optical properties indicates that Ti-GB has a large absorption coefficient in visible light range.

Wavelength-selective, time-resolved, and visible-light-responsive multicolor switching systems for multistate dynamic information encryption

Visible-light-responsive photoreversible multi-color switching systems (PMCSSs) are attractive to meet the advanced demands in dynamic information encryption. Particularly, PMCSSs with wavelength-selective and time-resolved color switching are highly important but underexplored. Here, a new strategy is proposed to realize wavelength-selective, time-resolved, and visible-light-responsive PMCSSs by integrating acetamide ligand-capping CdS (CdS-NH2) nanoparticles and various redox dyes in solid films for multistate dynamic information encryption. The –NH2 groups of surface-bounded CH3CONH2 act as sacrificial electron donors for scavenging photogenerated holes to endow the CdS-NH2 nanoparticles high photoreductive ability and activity in a broad visible light range from 400 to 515 nm, thus enabling the long-waited wavelength-selective multicolor switching via coupling the wavelength-dependent photoreductivity of CdS-NH2 nanoparticles and the discoloration kinetics of redox dyes, such as methylene blue (MB) and phenosafranine (PS). Moreover, the time-dependent color switching during recoloration process of the color switching system can be modulated by tuning the oxidation kinetics of MB and methylene green (MG), enabling time-resolved dynamic imaging characteristics. Based on the unusual properties of the PMCSSs, a kind of wavelength-selective and time-resolved codes are designed for advanced dynamic information encryption. This work provides new guidance for developing of new PMCSSs for information encryption with high security requirements.

Carbon nanotubes induced the enhancement of Raman scattering performance in silver thin films

In this study, Ag/CNTs composite films with excellent properties of surface-enhanced Raman scattering (SERS) were fabricated. The SEM images show that the template effect and stress concentration area of carbon nanotubes (CNTs) can not only induce the growth of Ag nanoparticles, but effectively increase the number and intensity of "hot spots". Due to the introduction of CNTs, the plasma absorption peak of Ag/CNTs composite films was observed to be enhanced in the range of visible light. The as-deposited Ag/CNTs samples showed high sensitivity and good temporal stability in the detection of MB probe molecules, with the detection limit of 10−9 mol/L and the enhancement factor of 6 × 105, respectively. In addition, the enhancement contribution of the substrate was further investigated by Finite difference time domain simulation, and the simulation results were consistent with those of the experimental results, which indicate that the synthesized Ag/CNTs thin films have potential application prospect in SERS technology.

Flexible, transparent, and durable slippery liquid‐infused porous surface achieved by void‐centered PVDF‐co‐HFP membrane for self‐cleaning antifog coating

AbstractBioinspired smart surfaces, such as slippery liquid‐infused porous surfaces (SLIPS), have garnered significant attention due to their efficacy in self‐cleaning, antifouling, and antibacterial applications. Despite their advantages, SLIPS exhibit limitations such as compromised transparency, insufficient stability, and limited slippery performance, which have hindered their widespread practical use. To address these challenges, this article proposes a rational design utilizing a void‐centered poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF) membrane for slippery liquid‐infused porous surfaces with exceptional flexibility, transparency, durability, and superior slippery performance. These advancements promise to enhance high‐performance, self‐cleaning, and antifogging coatings. The membranes, featuring large‐area, thickness‐customizable void‐centered PVDF, are fabricated through a two‐step process involving phase separation and selective etching. The utilization of PVDF polymer, which has a refractive index similar to that of silicon‐based lubricant oil, enhances transparency, while macrovoids positioned at the membrane's center, acting as oil reservoirs, improve the stability and performance of the SLIPS surfaces. Experimental findings demonstrate remarkable transparency of up to 93% in the visible light range and a lubricant oil uptake of 2.32 at a porosity of 70%. Moreover, the developed SLIPS exhibit outstanding durability, maintaining slippery performance with sliding angles of <10° following exposure to either 400 consecutive droplets or aging for up to 40 days. This study significantly contributes to the development of future SLIPS, particularly for applications such as antifogging coatings on vehicle glass and solar panels, and self‐cleaning surfaces.

Ag-bridged Z-scheme AgI/NU-1000 heterojunction for enhanced photocatalytic degradation of sulfamethazine: Pathways, mechanism insight, and DFT calculations

Constructing heterojunction structures is a crucial approach for improving carrier separation efficiency and expanding the visible-light absorption range of photocatalysts. Herein, a series of Ag-bridged Z-scheme (AgI/NU-1000) heterojunction photocatalysts were successfully prepared using a simple in-situ precipitation method. The photodegradation efficiency of the AgI/NU-1000 samples was assessed by degrading sulfamethazine under visible-light conditions. The optimized AgI/NU-10000.35 (AN-2) photocatalyst exhibited exceptional photodegradation activity, achieving a degradation rate of 89.68 % within 40 min. The toxicity test results proved that the solution degraded by AN-2 exhibited no detrimental effects on biological growth, thereby demonstrating its potential practical application value. Electrochemical and photochemical tests demonstrated that the creation of a Z-scheme heterojunction was favorable for the separation of photogenerated carriers. Density functional theory (DFT) calculations and X-ray photoelectron spectroscopy were used to clarify the electron migration direction within the AgI/NU-1000 heterojunction. Possible degradation pathways and mediate products were investigated using high-performance liquid chromatography–mass spectrometry and DFT calculations. This work demonstrates the potential application of AgI/NU-1000 composite materials in environmental treatment.

Ultrabroadband invisibility cloaking design of a concentric multilayered cylindrical metamaterial

An ultrabroadband invisibility cloak is designed using a genetic algorithm (GA) for a cylindrical target with an infinite length. The cloaking band is 0.4 to 0.7µm, covering almost the entire visible light range. The invisibility cloaking medium consists of concentric multilayered cylindrical metamaterials (CM). When the cloaking target is covered with a well-designed 26+ layer CM, the average scattering cross-section is 6% or less of the uncloaked target’s cross-section. The cloaking performance of the structure designed by the GA was superior to that designed by analytical calculations based on a combination of the transformation optics and the effective medium approximation. The cloaking is confirmed through the time variation of the magnetic fields calculated using the finite-difference time-domain method. In addition, the mechanism of the cloaking is discussed.

First-principles calculation of structural, electronic, optical, and mechanical properties of SrVO3.

CONTEXT AND RESULTS: In this paper, the crystal structure, electronic, optical, and mechanical properties of SrVO3 have been systematically studied by first-principles calculation. The results show that the calculated lattice parameters are in good agreement with the experimental values of X-ray diffraction. The density of states is described in detail in this paper. By analyzing the crystal structure and electronic properties of SrVO3, the magnetic properties of SrVO3 are obtained from the one unpaired electrons of V and the exchange interaction between two V ions. At the same time, a detailed analysis of the optical properties of SrVO3 was conducted, and it was found that it is transparent in the visible light range. Finally, the mechanical properties of SrVO3 are calculated, which can provide some references for future research. COMPUTATIONAL METHOD: In this paper, a first-principles method based on density functional theory (DFT) is reported for PBE-GGA analysis using the plane wave-pseudo potential method in a quantum concentrate packet, U value of 7 eV to V-d and a U value of 2 eV to O-p, Grimme correction by DFT-D method. The k points in the Brillouin region are set to 4 × 4 × 4. The energy convergence criterion for self-consistent field calculation is set at 5.0 × 10-6 eV/atom, and the cutoff energy is 1170eV. In this paper, the force acting on each atom is not more than 0.01 eV/Å, the maximum stress is not more than 0.02GPa, and the maximum atomic displacement is 5 × 10-4Å.

Near-Full-Spectrum Emission Realized in a Single Lead Halide Perovskite across the Visible-Light Region.

The engineering of tunable photoluminescence (PL) in single materials with a full-spectrum emission represents a highly coveted objective but poses a formidable challenge. In this context, the realization of near-full-spectrum PL emission, spanning the visible light range from 424 to 620 nm, in a single-component two-dimensional (2D) hybrid lead halide perovskite, (ETA)2PbBr4 (ETA+=(HO)(CH2)2NH3 +), is reported, achieved through high-pressure treatment. A pressure-induced phase transition occurs upon compression, transforming the crystal structure from an orthorhombic phase under ambient conditions to a monoclinic structure at high pressure. This phase transition driven by the adaptive and dynamic configuration changes of organic amine cations enables an effective and continuous narrowing of the band gap in this halide crystal. The hydrogen bonding interactions between inorganic layers and organic amine cations (N-H⋅⋅⋅Br and O-H⋅⋅⋅Br hydrogen bonds) efficiently modulate the organic amine cations penetration and the octahedral distortion. Consequently, this phenomenon induces a phase transition and results in red-shifted PL emissions, leading to the near-full-spectrum emission. This work opens a possibility for achieving wide PL emissions with coverage across the visible light spectrum by employing high pressure in single halide perovskites.

Low-threshold green lasing in heterogeneously integrated InGaN-based micro-rings covered by distributed Bragg reflectors on Si (100)

In this work, combining a series of wafer bonding, laser lift-off and chemical mechanical polishing processes, submicron-thick wafer-scale GaN-based thin-film epilayers are successfully transferred on Si (100), which provides a heterogeneous platform for fabricating microcavities for nitride-based integrated photonics. Low-threshold lasing via optical pumping from these transferred dry-etched green micro-ring cavities on Si is demonstrated by covering the whole micro-rings with dielectric distributed Bragg reflectors (DBRs), which greatly reduces the lasing threshold upon a better optical confinement at the ring rim. A high quality-factor of ∼3800 can be observed from the micro-rings beyond the lasing threshold under pulsed excitation conditions. Furthermore, room-temperature continuous-wave (CW) lasing at a wavelength of 521.7 nm with an ultralow threshold of 0.35 kW/cm2 is achieved. Our results suggest the use of a burying DBR layer notably improves the WGM microcavity confinement, providing insights for the design of low-threshold micro-lasers and low-loss waveguides for potential integrated photonic applications in the visible light range on the Si platform.