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Cathode Interface Engineering Approach for a Comprehensive Study of the Indoor Performance Enhancement in Organic Photovoltaic
摘要： Organic photovoltaic (OPV) has a prospective future as a reliable energy harvesting to drive low power consumption devices for indoor applications. In this article, the outdoor (1 sun) and indoor (LED 2700K) performance of PTB7-Th:PC70BM inverted OPV with three different solution-processed electron transport layers (ETL = PFN, TiOx, and ZnO) were compared. The morphology, optical, and electrical measurements indicate the strong dependency of the OPV performance with the illumination conditions. The sample with PFN-ETL that shows the highest outdoor performance with power conversion efficiency (PCE) of 10.55% and the best-reported fill factor (FF) of 75.00% among PTB7-Th:PC70BM-based OPV, surprisingly exhibits the lowest performance when illuminated under 250–2000 lux LED 2700K. Meanwhile, the lowest outdoor performance performed by ZnO with PCE of 10.03% displays the best indoor performance with the PCE of 13.94% under 1000 lux and a PCE of up to 16.49% under 1750 lux LED lamp, respectively. The changes in the FF values can be estimated by incorporating the parasitic resistance effect due to the type ETL used. Besides, using impedance spectroscopy, we observed that indoor performance agreed well with the trend of charge collection efficiency.
关键词： impedance spectroscopy,Organic photovoltaic,electron transport layers,PTB7-Th:PC70BM,indoor performance
更新于2025-09-23 15:21:01
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AC Impedance Spectroscopy, Conductivity and Optical Studies of Sr doped Bismuth Ferrite Nanocomposites
摘要： Effect of Sr doping on the structural, optical, dielectric, impedance properties of citrate combustion reaction route prepared Bi1-xSrxFeO3 (BSFO) nanocomposite has been investigated. The study of Fourier Transform Infrared Spectroscopy confirms the formation of perovskite structure of the Sr doped bismuth ferrite samples. SEM analysis shows decrease in grain size with increasing Sr concentration in BSFO nanocomposite. UV–visible absorption spectra in the spectral range 1.0–3.5 eV showed two doubly degenerate d–d transitions and two charge transfer transitions and optical band gap is found to decrease from 2.14 to 2.05 eV with increasing Sr concentration. Studies of frequency and temperature dependences of dielectric permittivity, impedance and electric modulus of the materials in broad frequency (20 Hz- 1 MHz) and temperature (30o C – 500oC) ranges using a complex impedance spectroscopy technique have provided interesting information on the contribution of the microstructure in these parameters. It has been observed that dielectric constant and dielectric losses decreases as the doping of Sr increased from x=0.1 to x=0.3 and attained a maximum value for BSFO (x = 0.1) sample. Impedance analysis indicates the presence of grain (bulk) and grain boundary resistive contributions which are found to increase with the increased Sr content. The ac conductivity of the samples is found to be frequency and temperature dependent and also vary with extent of Sr doping in BFO. Charge transport through short as well as long range conduction contributions has been indicated in different temperature regions of conductivity studies.
关键词： dielectric response,complex impedance spectroscopy,microstructure,Bismuth ferrite
更新于2025-09-23 15:21:01
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The Origin of Photoinduced Capacitance in Perovskite Solar Cells: Beyond Ionica??toa??Electronic Current Amplification
摘要： Photoinduced capacitances of perovskite solar cells exhibit peculiarities such as an apparently high capacitance and an inductive feature, so-called negative capacitance, which are not easily explained with typical carrier dynamics. Consequently, the origins of the photoinduced capacitances in perovskite solar cells have been intensively debated over the past several years. Here, the photoinduced capacitances of perovskite solar cells are analyzed by impedance spectroscopy. The analysis clarifies that the photoinduced capacitances of perovskite solar cells comprise several Debye relaxation-type capacitance components. Among these components, the photoinduced capacitance in the low-frequency range is attributed to ionic-to-electronic current amplification. However, the photoinduced capacitances in the middle- and high-frequency ranges originate from bipolar injection. The clear elucidation of the origins of the photoinduced capacitances in perovskite solar cells provides comprehensive insights for analyzing properties of perovskites in either the time or frequency domain.
关键词： perovskite solar cells,impedance spectroscopy,ionic to electronic response,negative capacitance
更新于2025-09-23 15:21:01
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Impact of the implementation of a mesoscopic TiO2 film from a low-temperature method on the performance and degradation of hybrid perovskite solar cells
摘要： High efficiencies of over 20% have been reported in the literature for both planar and mesoscopic hybrid perovskite solar cells, and the preferred configuration for scale-up and commercialization is still a matter of debate. The mesoscopic configuration generally requires a high-temperature processing step, which limits applications and makes the process less cost-effective. We have used low-temperature (LT) processing (≤120 °C) to fabricate high-efficiency planar and mesoscopic TiO2-based hybrid perovskite solar cells with comparable performance, highlighted by a champion LT mesoscopic solar cell with 16.2% efficiency. Photovoltaic efficiencies of 14–16% have been achieved for a mesoporous film thickness ranging from 120 to 480 nm by fine-tuning the precursor solution chemistry. The presence of the LT mesoporous layer improves the preservation of performance under conditions of relative humidity of 60%, especially under illumination. Impedance spectroscopy illustrates a similarity of the locus and kinetics of the recombination processes for both configurations. However, inductive loops usually related to ion migration are observed showing different characteristics between both configurations, pointing to the previously suggested correlation between ion migration and degradation. These results suggest that the beneficial role of a mesoporous TiO2 layer might be the stabilization of harmful defects at the perovskite/electron extraction layer interface, and indicate that interface engineering is critical to achieving improved long-term performance.
关键词： Low temperature TiO2,Perovskite solar cells,Impedance spectroscopy,Interfacial degradation
更新于2025-09-23 15:21:01
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Effect of the corona treatment on the microstructure of PVDF probed by electrochemical impedance spectroscopy
摘要： The microstructure of Polyvinylidene Fluoride (PVDF) membrane treated by corona was investigated in this study. The crystalline structure of PVDF membrane was con?rmed by x-ray diffraction (XRD), and the hole structure was evaluated by electrochemical impedance spectroscopy (EIS). It was found that the β phase appears in XRD pattern for treated PVDF, implying the polarization during corona treatment. The variation of membrane resistance suggested that the hole structure of PVDF became more porous with increasing treated time from 0 h to 2 h ?rstly, then became denser with treated time from 2 h to 4 h, and ?nally cracked at the treated time longer than 4 h. All the results indicated that corona treatment would induce the change of the bulk structure of PVDF membrane.
关键词： polyvinylidene ?uoride,corona treatment,electrochemical impedance spectroscopy,hole structure
更新于2025-09-23 15:21:01
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Characterization of Graphite/ZnO Schottky Barriers Formed on Polar and Nonpolar ZnO Surfaces
摘要： The authors demonstrate that the electrical properties of Schottky junctions fabricated by the deposition of colloidal graphite strongly depend on the crystallographic orientation of the ZnO substrate. The current-voltage, capacitance-voltage, and impedance measurements indicate that near-ideal Schottky junctions form on c-plane, while on a- and m-plane the junctions are laterally inhomogeneous. This behavior is assigned to higher concentration of native point defects in the near-surface region of nonpolar ZnO substrates. The authors further present an extended equivalent circuit model, which corresponds to actual structure of the junctions, and sheds light on their electrical transport properties.
关键词： impedance spectroscopy,graphite,equivalent circuit,ZnO,crystal polarity,Schottky contact
更新于2025-09-23 15:21:01
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Structural, electrical, dielectric properties and conduction mechanism of sol-gel prepared Pr0.75Bi0.05Sr0.1Ba0.1Mn0.98Ti0.02O3 compound
摘要： A detailed investigation of structural, electrical and dielectric properties of Pr0.75Bi0.05Sr0.1Ba0.1Mn0.98Ti0.02O3 manganite prepared by the sol-gel method was undertaken. The Rietveld refinement of X-ray diffraction pattern reveals that this compound is indexed in the orthorhombic structure with Pbnm space group. Structural properties are also analyzed by scanning electron microscopy and energy dispersive X-ray spectroscopy at room temperature. DC conductivity (σDC) data show the presence of a semiconductor-metal transition at TSM=360K. σDC is described by small polaron hopping model at high temperatures and variable range hopping model at low temperatures. AC conductivity results follow the universal Jonscher's power law at relatively low temperatures and Drude's model at high temperatures. The impedance plots display the contribution of both intra- and inter-granular contributions. Dielectric measurements exhibit highly remarkable dielectric permittivities useful in electronic devices. Dielectric losses are shown to be governed by the DC conduction mechanism and described by the Giuntini theory.
关键词： Electrical properties,Dielectric properties,Metal-semiconductor transition,Impedance spectroscopy
更新于2025-09-23 15:21:01
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Electrical transport properties and complex impedance investigation of Fe3+ and La3+ co-doping (Pb,Sr)TiO3 thin films
摘要： This work investigates the impact of Fe3+ and La3+ co-doping on the structural, electrical transport and dielectric relaxation properties of PST thin films. XRD and Raman spectroscopy data show that the Fe3+ and La3+ doping induce a pseudocubic to tetragonal structural phase transformation. Schottky barrier heights calculated from temperature-dependent current–voltage plots for the PST, PSTF and PSLTF films decreased to 1.20, 0.59, and 0.36 eV, respectively. This behavior was directly assigned to the increase in oxygen vacancies. The frequency dependence of sample’s impedance revealed the presence of the typical electrical relaxation phenomenon in all films. Activation energies calculated from the imaginary part of the impedance are 1.73 and 0.57 eV: the high value (1.73 eV, PST films) suggests the presence of long-range oxygen vacancy diffusion, while the lower one (0.57 eV PSLTF films) should be associated to the short-range oxygen vacancy diffusion.
关键词： Dielectric relaxation,Thin films,Electrical transport,Impedance spectroscopy
更新于2025-09-23 15:21:01
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[IEEE 2018 EMF-Med 1st World Conference on Biomedical Applications of Electromagnetic Fields (EMF-Med) - Split, Croatia (2018.9.10-2018.9.13)] 2018 EMF-Med 1st World Conference on Biomedical Applications of Electromagnetic Fields (EMF-Med) - Measurement of Weak Low Frequency Electromagnetic Field Effects on Cells
摘要： The aim of our research is a development of an automated experimental platform for identification of the effects of weak low frequency (LF) electromagnetic field (EMF) on cells. The platform comprises multiple measurement stations, allowing monitoring and subsequent characterization of cell cultures. Main detection methods include electroimpedance spectroscopy (EIS), optical microscopy, and turbidimetry. EIS provides information about cell culture growth and enables electrical characterization of cell structures. Morphology and cell kinetics are investigated via computer analysis of images obtained from video-microscopy. The complex measurement system allows efficient scanning of frequencies and amplitudes of EMF while searching for possible specific response of investigated biosystem. The developing platform aspires to contribute towards general methodology of investigation into LF EMF biological effects.
关键词： microscopy image analysis,impedance spectroscopy,COST EMF-MED,low frequency electromagnetic fields
更新于2025-09-23 15:21:01
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Current-voltage and capacitance study of light-induced metastabilities in CuZnSnSSe thin-film solar cells
摘要： White, red and blue light-induced metastabilities in Cu2ZnSnS4(Se4) solar cells were investigated by temperature dependent current-voltage measurements, drive level capacitance profiling, impedance and thermal admittance spectroscopy. A set of devices were studied where white and blue light soaking at room temperature led to degradation of the device performance, while after red light soaking the solar cell efficiency did not change. We observed a significant effect of light soaking on capacitance data measured in both low and high-temperature ranges for these devices. In particular, the net doping concentration extracted from drive-level capacitance profiling substantially increased after light soaking treatments. Low and high-temperature capacitance steps observed in the reference capacitance-frequency spectra were assigned to Fermi level pinning and bulk defects, correspondingly. Light soaking with different-wavelength light led to a shift of both steps toward the high-frequency range, and hence a decrease in the thermal admittance activation energies. A low-frequency “inductive” loop was detected in the impedance spectra after light soaking, regardless of wavelength. It was proposed that the appearance of the “inductive” loop is due to the formation of a negative electric field at the highly defected CdS/Cu2ZnSnS4(Se4) hetero-interface. This result also leads us to conclude that such electric field is responsible for the metastable behaviour of these devices at room temperature, while the low temperature metastable changes might have a different origin. We also discuss the methodology for electrical characterization of the metastable solar cells in detail.
关键词： impedance spectroscopy,metastability,kesterite solar cells,electrical characterization
更新于2025-09-23 15:19:57