Efficient and low-cost platinum-free counter electrodes are essential for the practical application of dye-sensitized solar cells (DSSCs). In this work, a metal–organic framework-derived porous carbon/polyaniline (MOF-C/PANI) hybrid counter electrode was developed to improve the electrocatalytic activity towards the iodide/triiodide (I−/I3−) redox couple. The MOF-derived carbon provides a high surface area and abundant electrocatalytic active sites. The conductive PANI network improves electron transport throughout the electrode. X-ray diffraction (XRD) confirmed the successful incorporation of PANI into the carbon framework without forming secondary crystalline phases. Scanning electron microscopy (SEM) showed a uniform PANI coating on the porous carbon framework and confirmed the formation of an interconnected hybrid structure. Brunauer–Emmett–Teller (BET) analysis revealed that the MOF-derived carbon possessed a specific surface area of 512 m2 g−1. The MOF-C/PANI hybrid retained a surface area of 356 m2 g−1. It also exhibited a pore volume of 0.52 cm3 g−1 and an average pore diameter of 6.1 nm. These characteristics facilitate electrolyte diffusion and provide easy access to catalytic active sites. Electrochemical characterization showed that the MOF-C/PANI counter electrode exhibited high electrocatalytic activity, delivering high cathodic peak current density, low charge-transfer resistance of 6.2 Ω and high exchange current density. The DSSC assembled with the MOF-C/PANI counter electrode achieved power conversion efficiency of 8.02
In this work, the primary focus is on investigating the structural, optical, and electrical properties of lanthanum- and cobalt-co-substituted BiFeO3 (BFO). Polycrystalline (Bi1−xLax)(Fe1−xCox)O3 (BLFCO) samples (where x = 0.0, 0.1, and 0.2) were synthesized using the conventional high-temperature solid-state reaction method. Room-temperature x-ray diffraction (XRD) analysis confirmed that all compositions crystallize in a rhombohedrally distorted perovskite structure with the R3c space group, suggesting that La3+ ions preferentially occupy the Bi3+ sites, while Co ions substitute for Fe ions at the B-site of the perovskite lattice. Scanning electron microscopy (SEM) revealed a systematic decrease in the average grain size with increasing La and Co co-substitution. Energy-dispersive x-ray spectroscopy (EDS) confirmed the presence of the constituent elements in the synthesized samples. The optical bandgap, determined from ultraviolet–visible (UV–Vis) spectroscopy, increased from 2.34 eV to 3.67 eV with increasing La and Co co-substitution. Frequency-dependent dielectric measurements revealed an increasing trend in the dielectric constant with increasing dopant concentration. Detailed analysis of the impedance spectra as a function of frequency and temperature enabled the separation and evaluation of the grain and grain-boundary contributions to the electrical response, including their respective resistive and capacitive characteristics.
Research on double-absorber solar cells, particularly the combination of lead-free metal halide perovskite with complementary secondary absorbers, has attracted significant research interest owing to its potential for improved spectral utilization. In this work, an all-lead-free double-absorber solar cell employing MASnI3 and antimony selenosulfide (Sb2(S1−x,Sex)3), as the primary and secondary absorbers, is proposed. Zinc sulfide (ZnS) and copper zinc germanium sulfide (CZGS) are employed as the electron transport layer (ETL) and hole transport layer (HTL), respectively. Four Se compositions (x = 0.1, 0.3, 0.5 and 0.7) are investigated using SCAPS-1D simulation software, with simulation parameters adopted from established theoretical and experimental studies. The ZnS ETL thickness is fixed at 100 nm, while 100 nm is selected for the CZGS HTL and as a practical reference thickness for Sb2(S1−x,Sex)3. The MASnI3 absorber is optimized at 700 nm. Based on band alignment and spectral complementarity analysis, the MASnI3/Sb2(S0.9, Se0.1)3 configuration demonstrates the best photovoltaic performance, with an 11.45
The (1−x) Ba0.7Sr0.3TiO3−xCa0.28Ba0.72Nb2O6 (abbreviated as (1−x) BST–xCBN, x = 0–0.15) ceramics were prepared by the solid-state reaction method, and the effects of CBN as the second phase on the ceramic structure, dielectric properties, and energy storage properties were systematically studied. The samples maintain a single perovskite phase for x < 0.09, and then a tungsten bronze phase appears and gradually increases with further increase in x, presenting a biphasic structure. When x ≥ 0.03, its Curie temperature is much lower than room temperature, accompanied by the phase transition from ferroelectric phase to paraelectric phase. The addition of CBN enhances ionic disorder in the BST structure, inducing the generation and increase of polar nano-regions (PNRs) and disrupting the long-range ferroelectric order. An ultra-high energy storage efficiency of of 97.4
In isolated direct current (DC)-to-DC converters, the leakage inductance of a high-frequency transformer has a pronounced impact on operational performance. Therefore, accurate prediction and effective control of leakage inductance are essential during transformer design. Under high-frequency operation, the leakage magnetic energy within the core window of a transformer decays owing to frequency-dependent effects. However, existing studies only consider the frequency-dependent behavior of the winding region, while overlooking the attenuation of leakage flux energy in regions other than the windings. To address this issue, this paper first investigates the attenuation characteristics of leakage magnetic energy in the non-winding region and then quantifies its contribution to the total attenuation in the core window. Based on the method of images, an analytical leakage inductance calculation method is proposed to simultaneously consider the frequency-dependent effects of leakage magnetic energy in both the winding region and non-winding region. Finally, experimental validation and comparative analysis are carried out using three round conductor transformer prototypes of different sizes. The results show that the average unsigned deviations of the proposed method for the three prototypes are 3.07
