Lead toxicity and phase instability are major challenges for CsPbI3 perovskite photovoltaics. To address these issues, we employ a combined theoretical approach using density functional theory (DFT) and SCAPS-1D simulations to investigate Sn/Mg (B-site, 12.5%) and Rb (A-site, 50%) co-doping strategies. Sn and Mg substitutions both shorten the central B-I bond lengths but modulate bonding character through distinct mechanisms: Sn enhances Sn-5p/I-5p covalent hybridization, while Mg strengthens ionic character. Both mechanisms contribute to suppressing halide vacancy formation and improving structural stability. Electronic structure calculations yield band gaps ranging from 1.23 to 1.45 eV (raw DFT band gaps), all within the ideal range for single-junction solar cells. Notably, Sn doping preserves a direct band gap and introduces intermediate states, while Mg doping induces an indirect transition and exhibits p-type semiconducting behavior. Subsequent Rb incorporation further fine-tunes the band edges. Optically, all compounds show strong visible-light absorption, with pristine and Sn, Rb co-doped CsPbI3 being particularly efficient for photon harvesting. Furthermore, Mg, Rb co-doped and pristine samples exhibit superior infrared dielectric response, which aids in suppressing carrier recombination. With the corrected band gaps, device simulation results identify Rb, Sn co-doped CsPbI3 as the optimal absorber material. After optimizing absorber layer thickness and defect density, the corresponding hole-transport-layer-free solar cell achieves a predicted power conversion efficiency of 24.49%. This work demonstrates that strategic A- and B-site co-doping can effectively balance structural stability, optoelectronic properties, and device performance, providing a viable pathway for developing high-efficiency, lead-reduced inorganic perovskite solar cells.

In this study, we demonstrate a differential absorption-enhanced method based on secondary diffraction spectra and apply it to the detection of sulfur dioxide based on differential optical absorption spectroscopy (DOAS). An effective approach for extracting the secondary diffraction spectrum is proposed. The absorption spectrum of sulfur dioxide achieved by secondary diffraction was confirmed to match that of primary diffraction in the vacuum ultraviolet region. The enhancement in differential absorption due to the improvement in resolving power was observed. Sulfur dioxide was calibrated and determined based on the primary and secondary diffraction spectra, respectively. When measuring sulfur dioxide concentrations, detection sensitivity and limit of detection (LoD) achieved 10-fold and two-fold improvements, respectively. This study provides a novel, to our knowledge, method for enhancing measurements based on DOAS.

Of growing interest in the field of photovoltaics is the development of environmentally benign, high-performance absorber materials to replace toxic lead-based perovskites. Cs2TeI6, a lead-free vacancy-ordered double perovskite, has emerged as a highly promising candidate due to its ideal bandgap and excellent optoelectronic properties. This study comprehensively investigates the photovoltaic potential of lead-free perovskite Cs2TeI6 through a combined approach of density functional theory calculations and SCAPS-1D numerical simulations. The results reveal that Cs2TeI6 exhibits a indirect bandgap of 1.242 eV, excellent optical absorption characteristics (>10(5) cm(-1)), and suitable band alignment, making it a promising absorber material for environmentally friendly solar cells. Through the systematic optimization of key device parameters, such as the electron transport layer material (TiO2, WS2, Cd0.5Zn0.5S, ZnO), absorber thickness (0.5-1.5 mu m), and defect density (10(12)-10(16) cm(-3)), the device with Cd0.5Zn0.5S as the electron transport layers (ETL) achieved a remarkable power conversion efficiency (PCE) of up to 28.85 % at a low defect density of 10(12) cm(-3). Furthermore, the effects of operating temperature (300-420 K), series resistance, and shunt resistance on performance were analyzed, demonstrating good thermal stability and practical feasibility. This work provides valuable insights into the design and optimization of high-efficiency, lead-free perovskite solar cells based on Cs2TeI6.

Metal halide perovskite nanomaterials, as a cutting-edge research direction in optoelectronics, have demonstrated immense potential in solar cells, light-emitting devices, and laser technologies in recent years. However, translating these advanced material research findings into comprehensive experimental courses suitable for undergraduates remains a challenge. This paper designs a complete experimental teaching scheme that employs a simplified ultrasonic synthesis method to prepare CsPbX3 perovskite nanocrystals (NCs) and combines spin-coating techniques to fabricate thin films, ultimately enabling the characterization of their amplified spontaneous emission (ASE) performance. This experiment can be conducted at room temperature and atmospheric pressure, significantly reducing experimental barriers and safety risks. Students systematically analyze the optical properties, morphological structure, and elemental composition of the NCs through characterization techniques such as UV-vis absorption spectroscopy, photoluminescence spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Furthermore, by performing spin-coating film preparation and ASE testing, students gain an intuitive understanding of the physical mechanisms underlying optical gain and threshold behavior. This experiment organically integrates nanomaterial synthesis, thin film preparation, and optoelectronic applications, not only strengthening students' comprehension of the "synthesis-structure-property" relationship in materials but also cultivating their interdisciplinary experimental design and data analysis skills, providing an essential practical platform for undergraduates to deeply explore frontier optoelectronic materials.

Surface-enhanced Raman scattering (SERS) remains hampered in complex matrices by the difficulty of selectively capturing trace analytes. In this study, we address this bottleneck with a simple electrochemical surfaceenhanced Raman scattering (EC-SERS) platform built on titanium dioxide (TiO2) nanotube arrays. Applying -0.5 V vs. Ag/AgCl recruits additional binding sites for carbendazim (CBZ) on the Ag/Au-TiO2 surface, which boosts the Raman signal 3.1-fold and delivers a 12.7-fold enhancement in sensitivity over conventional, zeropotential SERS method. After measurement, 365-nm UV illumination photocatalytically degrades the retained CBZ, restoring the substrate for reuse. Spiked vegetable extracts gave recoveries of 83.4-108.8%, values that coincide with HPLC-MS data within 80.2-101.0%. This regenerable semiconductor architecture expands the scope of TiO2-based SERS and establishes a practical route to sensitive, on-site pesticide screening.

Developing a fiber optic humidity sensor with exceptional performance remains a challenge, requiring simultaneous optimization of multiple parameters including cost, sensitivity, response/recovery, hysteresis, dynamic range, stability and temperature effect. Herein, we present fabrication of evanescent wave-based fiber optic humidity sensors using hierarchical porous yttrium chloride-doped carbon quantum dots (CQDs) as sensing material. CQDs were prepared by a hydrothermal process and were subsequently assembled on a plastic fiber core using a light-driven deposition technique. The sensor exhibited an optimal average sensitivity of 0.72 %/% RH, a fast response of 2.6 s (0.46 s by exhalation testing) and an excellent linearity with the determination coefficient R 2 of over 0.99 within a relative humidity (RH) range of 0-75 %. Furthermore, good long-term stability, repeatability and reproducibility were achieved with trivial temperature interference. We demonstrated accurate recognition of breathing patterns and real-time monitoring the onset of sleep apnea using the sensor without temperature cross-sensitivity.

This study presents a fiber-optic humidity sensor based on boron and nitrogen co-doped graphene quantum dots (B,N-GQDs). Hydrophilic B,N-GQDs film was fabricated by a hydrothermal method, followed by photo-driven deposition on plastic optical fiber cores. The sensor showed a wide response range (0-85%RH) with high sensitivity (0.0072/%RH), a low detection limit (0.2%RH), high linearity (R2=0.999), and rapid response (2.5 s). The sensor exhibited a low hysteresis and excellent stability. Good stability and promising applications in respiration and skin moisture monitoring were also demonstrated. The sensing mechanism is attributed to humidity-dependent adsorption of water molecules by the abundant hydrophilic groups of the film. This adsorption alters the film's refractive index and extinction coefficient, modulating the transmitted light intensity via a partial leaky-mode mechanism.

Confronted with environmental contamination and energy scarcity, lead-free vacancy-ordered double perovskite Cs2TeX6 (X = Cl, Br, I) has shown promising potential for optoelectronic applications. In this work, Cs2TeCl6 was synthesized by mechanochemistry with its structure characterized using X-ray diffraction, the aligning of experimental and computational results demonstrate the reliability of the geometrically optimized crystal. First principles calculation was conducted to analyze the evolutions of mechanical, optoelectronic and thermodynamic properties of Cs2TeX6 under hydrostatic pressure from 0 GPa to 40 GPa. Calculated modulus satisfy the stability criteria, indicating structural ductility and stability. Pressure application diminishes lattice parameters and notably narrows their indirect band gaps approach the ideal 1.34 eV for perovskite solar cells at 29.3 GPa, 8.3 GPa, and 0.1 GPa when X goes from Cl to I. The analysis of differential charge density slice under pressure elucidates materials’ photoelectric shifts from the basic electronic alterations, which is a novel research perspective. The density of states results show that the valence band maximum is dominanted by X-p orbitals, while the conduction band minimum by Te-5p and Cs-6s orbitals. Their improved absorption coefficients and dielectric constants under pressure position them as promising materials for applications in perovskite solar cells. Positive phonon spectrum and rapidly decreasing negative Gibbs free energy with temperature confirm the thermal stability of these materials. Finally, the photovoltaic performance of Cs2TeI6-based cell structures was investigated at varying pressure using SCAPS-1D simulator. The maximum power conversion efficiency was found 22.64 % at 0.1 GPa. This work provides a scientific basis for experimental studies and directions for guiding the modulation of perovskites’ optoelectronic performance through hydrostatic pressure.

In this paper, we reported a simple method to grow Zinc oxide thin films with a hybrid structure of nanoplates and nanorods. As far as we know, no other researchers have obtained ZnO films with this special morphology by sol-gel method. Both X-ray diffraction and photoluminescence indicate that these films have good crystalline quality. In order to test the photocatalytic performance of the samples, a common organic dye, methylene blue (MB), was selected as the photodegradation target. Compared to ZnO films with tightly packed grains and smooth surfaces, the one with a hybrid structure of nanoplates and nanorods exhibits higher photocatalytic efficiency. It is attributed to its higher surface area and easier migration of holes and electrons excited by light to the surface of ZnO nanoplates and nanorods to participate in redox reactions.

In this study, we demonstrate fabrication of an evanescent wave fiber optic humidity sensor based on PEG-PMMA microsphere film as moisture-sensitive material. A three dimensional stacking structure of PEG-PMMA microspheres is formed by dip coating method on fiber core. A simultaneous fast response and recovery is optimized with equilibrium time of 13 s and 8 s between 30%RH and 80%RH, respectively. The sensor possessed a maximum sensitivity of 157.143 lux/%RH in the range of 70-80%RH and a good linear relationship between the logarithm of output optical intensity and relative humidity with a correlation coefficient of 0.998. Moreover, the sensor exhibits low hysteresis, excellent repeatability, short-term and long-term stability and electromagnetic immunity. Modulation of intensity is primarily attributed to scattering of evanescent wave on polymer microspheres in humidity sensing.

A differential fiber optic humidity sensor based on superhydrophilic SiO2/polyethylene glycol (PEG) composite film is presented. With exposure to humid air, the physical properties of SiO2/PEG composite film coated on the sensing region changes, disturbing transmission of evanescent wave of fiber and leading to change of the output light intensity of sensing fiber. The output light intensity of humidity sensor increases with the increase of relative humidity (RH), which is attributed to the expansion of polymeric film and less scattering of light. The sensor shows a linear response of the ratio of output light intensity of sensing fiber to that of reference fiber IS/IR to RH with a correlation coefficient of 0.991 in the range of 11-81 %RH. The ratio IS/IR is independent of the intensity of optical source, indicating that differential sensor structure enables humidity testing immune to instability of light source. In addition, the sensor possesses excellent reversibility, stability and repeatability.

An intensity-modulated fiber optic evanescent wave humidity switch sensor is developed using PEG/PVA thin film as a moisture-sensitive layer. Effects of precursor solution concentration, mass ratio of PEG to PVA and PEG molecular weight were optimized on switch performance. Switch sensing characteristics was achieved with an optimal sensitivity of 1708 lux/%RH and sensitivity increase of over 103 fold at the threshold humidity level. The sensor shows a fast recovery of 3 s, a low hysteresis, and remarkable stability and repeatability. Switch behavior is attributed to the phase transition of PEG at the threshold humidity level, causing changes in the sensing film's refractive index and scattering of evanescent wave.

CsPbBr3 perovskite has garnered significant attention in the field of optoelectronics due to its exceptional photoelectric properties. In this study, we report the fabrication of a piezoelectric nanogenerator (PNG) composed of a composite of monoclinic phase CsPbBr3 nanocrystals and polydimethylsiloxane. This is the first instance of a PNG based on the monoclinic phase of CsPbBr3. The PNG device has been optimized to operate at a frequency of 30 Hz and exhibits impressive output performance, generating a peak-to-peak output voltage of 50 V, an output current of 5.5 mu A and a power density of 2.5 mu W cm-2 when subjected to an applied force of only 4.2 N over an effective area of 8 cm2. The energy generated by this PNG can be efficiently collected using capacitors with a high energy conversion efficiency of 21.7%. Furthermore, the output voltage of the PNG remains at 98.5% of its initial value after 20 days, demonstrating exceptional stability. This study highlights the great potential of CsPbBr3 perovskite materials for the simple and cost-effective fabrication of high-performance multifunctional piezoelectric energy harvesting devices.

Fabrication of an evanescent wave fiber optic humidity sensor based on bromophenol blue (BPB) doped SiO2 thin film was demonstrated, modulating in light intensity. The sensing film was coated on fiber core via a single-step dip coating method, followed by sol-gel processing of precursor. A good exponential relationship was established between output light intensity and relative humidity. The sensor exhibited a high sensitivity and fast response and recovery, as well as low hysteresis, good stability and repeatability. Adsorption of ambient water triggered a ring-opening reaction of BPB, which enhanced light absorption of the sensing film significantly and affecting transmission of evanescent wave.

Low efficiency of photogenerated electron-hole separation has been a challenge for organic conjugated polymer photocatalysts. Our preceding studies have revealed that polymers containing B <- N coordination bonds can form a localized built-in electric field that effectively promotes photogenerated charge separation. However, B <- N coordination units are still scarce and require more examples to find regularities in their structural design. The systematic development and testing of B <- N coordination units is necessary for the efficient development of subsequent polymers containing B <- N coordination bonds. In this work, three conjugated polymers containing B <- N coordination bonds, PBN-Ni, PBP-Ni, and PBS-Ni, were synthesized by changing the substituents of the boron atoms and introducing narrow-band thiophene units to form conjugate and energy band gradients. The energy band modulation and localized built-in electric field construction were both achieved as planned, while the bandgap and photogenerated charge transport capabilities caused performance discrepancies. The experimental results showed that PBN-Ni had a better photocatalytic hydrogen evolution (HER) performance, reaching 104.6 mu mol h(-1) (lambda > 420 nm). The optimal optical absorption edge of PBS-Ni was up to 643 nm, but the HER was lower, at 33.2 mu mol h(-1) (lambda > 420 nm, 1% Pt). PBP-Ni optimized some of the optical absorption efficiencies (511 nm) while ensuring the HER activity (96.6 mu mol h(-1), lambda > 420 nm). This work tentatively explores the characterization of the B <- N coordination bond-containing base units serving as photocatalysts and provides the basic model experience and data reference for the subsequent expansion of B <- N coordination bond-containing units and the development of B <- N coordination bond-containing copolymer systems.

Employing functional and structured thin films on fiber optic sensors has tremendously improved capabilities in humidity sensing applications. In this paper, we demonstrate fabrication of a fiber optic evanescent wave humidity sensor based on S i O 2/porous polymethyl methacrylate (PMMA) thin films. With the exposure to moisture, S i O 2/porous PMMA thin films absorb water molecules. The refractive index and absorption coefficient of thin films change with ambient humidity, resulting in modulation of the light intensity transmitted in fiber. A good linearity is determined between the logarithm of output light intensity and relative humidity (RH). An optimal average sensitivity of 188.3 lux/%RH is achieved with an increase of 11.7 fold in the RH range of 5% to 95%. The response and recovery times are 8 s and 23 s, respectively. Furthermore, the sensor exhibits low hysteresis, and excellent stability and repeatability.

CsPbX 3 (X = Cl, Br, I) nanocrystals (NCs) are competitive materials for a wide range of applications because of their outstanding optoelectronic properties. Ion doping has been demonstrated as one powerful method for improving the optical properties of CsPbX 3 NCs. However, the conventional ion‐doping approaches are tedious, and generally performed under an inert atmosphere and high temperature. In this work, a one‐step ultrasonic‐assisted approach is demonstrated to prepare doped CsPbX 3 NCs. To demonstrate the universality of the ultrasonic‐assisted ion‐doping approach, three ion‐doped perovskite NCs are prepared, which represent three common improvements effects of ion doping on perovskite NCs, namely improved stability, PL emission, and photoluminescence quantum yields (PLQYs) of perovskite NCs. Sr‐doped CsPbI 3 NCs showed improved phase stability. Mn‐doped CsPbCl 3 NCs showed dual‐color emissions at 406 and 580 nm. The PLQYs of the as‐prepared Ni‐doped CsPbCl 3 NCs are greatly improved, from 10.1% to 71%. Such a simple and versatile ion‐doping approach may promote the practical applications of all‐inorganic perovskite NCs.

Solar energy is pollution‐free with less impact on the ecosystem, but it has limitations due to its intermittent nature attributed to sun availability for specific hours, resulting in less energy conservation efficiency. Similar to the purpose of carvings on the leaves to collect water, we are presenting a nanometer‐thick layer of silicon or chalcogenide with fused silica for photons enhancement in red and the blue portion of the spectrum within the solar energy reaching the earth's surface. The design is based on nanorod imprints on micrometer‐sized conventional fused silica, ensuring better absorption and transportation toward hybrid photovoltaic cells. Hybrid solar cells (comprising silicon and perovskites) are typically termed the future of solar power, but will not be discussed here. Effective area, optical power concentration, and second‐ and higher‐order dispersions can further help design and develop the photon concentrators.

为了更好地提高布里渊光时域反射仪(Brillouin optical time domain reflectometer,BOTDR)系统采集信号的信噪比,尽可能消除系统噪声对信号的干扰,提出了一种基于改进小波阈值的去噪算法.该算法选取bior5.5作为小波基进行5层小波分解,使用改进的阈值方法对每一层信号系数进行去噪.该阈值函数不但克服了硬阈值函数不连续的缺点,还解决了软阈值函数的恒定偏差问题,同时还能够有良好的适应性.实验结果表明,使用该算法,去噪后的信号更加平稳,信噪比相较于硬、软阈值去噪算法平均提升了约1.6、6.4 dB,均方误差平均减少约0.17、0.91,去噪效果显著提升,验证了该算法的有效性.

A fiber optic humidity sensor based on polyvinyl alcohol (PVA)/Tween 20 film has been fabricated by modulating the intensity of light transmitted in optical fiber. PVA/Tween 20 film was used as the cladding and humidity-sensitive material of optical fiber. The logarithmic of output light intensity exhibited a linear increase with the increase of humidity (22%-82%RH). With the addition of Tween 20 in the formation of film, average sensitivity increased by 13-fold. Fast equilibrium on adsorption and desorption of water molecules were also achieved on the film. The response and recovery times were determined to be 11 s and 9 s, respectively. Moreover, the sensor possesses good repeatability. The sensing mechanism was probably based on the swelling of PVA after adsorbing water molecules, which affected scattering of evanescent waves in the cladding. The output light intensity varied with the decay of evanescent waves.