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Spectral dynamics of shift current in ferroelectric semiconductor SbSI
摘要： Photoexcitation in solids brings about transitions of electrons/holes between different electronic bands. If the solid lacks an inversion symmetry, these electronic transitions support spontaneous photocurrent due to the geometric phase of the constituting electronic bands: the Berry connection. This photocurrent, termed shift current, is expected to emerge on the timescale of primary photoexcitation process. We observe ultrafast evolution of the shift current in a prototypical ferroelectric semiconductor antimony sulfur iodide (SbSI) by detecting emitted terahertz electromagnetic waves. By sweeping the excitation photon energy across the bandgap, ultrafast electron dynamics as a source of terahertz emission abruptly changes its nature, reflecting a contribution of Berry connection on interband optical transition. The shift excitation carries a net charge flow and is followed by a swing over of the electron cloud on a subpicosecond timescale. Understanding these substantive characters of the shift current with the help of first-principles calculation will pave the way for its application to ultrafast sensors and solar cells.
关键词： photovoltaic effect,ferroelectricity,picosecond techniques,solar cells,bulk matter
更新于2025-09-19 17:15:36
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Alternating Current Photovoltaic Effect
摘要： It is well known that the photovoltaic effect produces a direct current (DC) under solar illumination owing to the directional separation of light-excited charge carriers at the p–n junction, with holes flowing to the p-side and electrons flowing to the n-side. Here, it is found that apart from the DC generated by the conventional p–n photovoltaic effect, there is another new type of photovoltaic effect that generates alternating current (AC) in the nonequilibrium states when the illumination light periodically shines at the junction/interface of materials. The peak current of AC at high switching frequency can be much higher than that from DC. The AC cannot be explained by the established mechanisms for conventional photovoltaics; instead, it is suggested to be a result of the relative shift and realignment between the quasi-Fermi levels of the semiconductors adjacent to the junction/interface under the nonequilibrium conditions, which results in electron flow in the external circuit back and forth to balance the potential difference between two electrodes. By virtue of this effect, the device can work as a high-performance broadband photo detector with extremely high sensitivity under zero bias; it can also work as a remote power source providing extra power output in addition to the conventional photovoltaic effect.
关键词： nonthermal equilibrium state,quasi-Fermi levels,excessive carriers,AC photovoltaic effect,photovoltaic effect,alternating current
更新于2025-09-19 17:13:59
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Polarization tunable and enhanced photovoltaic properties in tetragonal-like BiFeO3 epitaxial films with graphene top electrode
摘要： Ferroelectric photovoltaic materials have attracted intensive interest due to their intriguing above-bandgap photovoltage, while the low photocurrent limits their further device applications. In this work, both enhanced and tunable photovoltaic effect (PVE) are demonstrated in sandwiched structure of Graphene/tetragonal-like BiFeO3/Ca0.96Ce0.04MnO3 (Graphene/T(-like) BFO/CCMO). The epitaxial BFO film is grown on the CCMO buffered LaAlO3 substrate by pulsed laser deposition and the mechanically exfoliated graphene is transferred directly onto the BFO film as top electrode. The optimized open circuit voltage (Voc) and short circuit current density (Jsc) are measured to be (cid:1)0.88 V and 2.56 mA/cm2, respectively. Moreover, the photovoltaic response can be modulated by controllable ferroelectric polarization, whereby both the Voc and Jsc show piezoresponse-like hysteresis behaviors against voltage. The notably enhanced PVE is likely a result of the combination effects of large polarization in the T(-like) BFO film, partially unscreened depolarization field, high transmittance and conductivity of the graphene top electrode. This work clearly indicates the potential of Graphene/ferroelectric photovoltaic devices for memory and energy conversion applications.
关键词： Photovoltaic effect,Polarization,Graphene,Tetragonal-like BiFeO3
更新于2025-09-19 17:13:59
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Plasmonic gold nanorods mediated p-BFCrO/n-rGO heterojunction in realizing efficient ferroelectric photovoltaic devices
摘要： In this work, we introduce a chemically synthesised lead-free ferroelectric thin film 2% Cr doped BiFeO3 (BFCrO) for possible photovoltaic (PV) applications. The first set of PV devices were fabricated onto ITO/glass electrode by utilizing BFCrO as an active material and Pt as top electrode. The obtained ferroelectric and electrical results were systematically compared with the conventional BFO and the BFCrO device was found to be a potential one. To further enhance the PV performance, highly conducting n-type reduced graphene oxide (rGO) was heterogeneously employed as an electron transport layer (ETL) in between ITO and BFCrO. Surprisingly, the JSC was significantly improved by 1000 times along with amended VOC and FF as compared to the standalone BFCrO device. Furthermore, an attempt has been made to embed plasmonic Au nanorods (NRs) in between rGO and BFCrO, which alleviates the absorbance in heterojunction through localized surface plasmonic effect, ultimately offered remarkable PV performances than conventional BFO one. The Au NRs based BFCrO/rGO PV device exhibited an increased VOC and JSC of 0.63 V and 2.56 mA/cm2, respectively as compared to the BFCrO/rGO device with VOC (0.56 V) and JSC (1.54 mA/cm2). Effort was devoted to establish ferroelectricity in BFCrO and the effect of positive and negative polarizations on J-V measurements were observed in with or without Au NRs based devices. The modulation in charge transport with polarization field and improved photoresponse were explained by projecting a band diagram, which also provides a comprehensive understanding on the operation principle of the fabricated devices.
关键词： Ferroelectric polarization,Heterointerface,Photovoltaic effect,Electron transport layer,Plasmon resonance
更新于2025-09-19 17:13:59
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Solar Hydrogen Production || Solar photovoltaics (PV)
摘要： The photovoltaic conversion is based on the photovoltaic effect, that is, on the conversion of the light energy coming from the sun into electrical energy. To carry out this conversion, devices called solar cells are used, constituted by semiconductor materials in which a constant electric field has been created artificially (by means of a pn junction). Next, we will try to understand in a qualitative way how light is converted into electricity. This requires remembering some concepts of physics and chemistry.
关键词： light energy,solar cells,pn junction,photovoltaic effect,semiconductor materials,electrical energy
更新于2025-09-19 17:13:59
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Thin Films Based on Cobalt Phthalocyanine:C60 Fullerene:ZnO Hybrid Nanocomposite Obtained by Laser Evaporation
摘要： Matrix-assisted pulsed laser evaporation (MAPLE) was used to deposit hybrid nanocomposite thin films based on cobalt phthalocyanine (CoPc), C60 fullerene and ZnO nanoparticles. The inorganic nanoparticles, with a size of about 20 nm, having the structural and optical properties characteristic of ZnO, were chemically synthesized by a simple precipitation method. Furthermore, ZnO nanoparticles were dispersed in a dimethyl sulfoxide solution in which CoPc and C60 had been dissolved, ready for the freezing MAPLE target. The effect of the concentration of ZnO nanoparticles on the structural, morphological, optical and electrical properties of the CoPc:C60:ZnO hybrid nanocomposite layers deposited by MAPLE was evaluated. The infrared spectra of the hybrid nanocomposite films confirm that the CoPc and C60 preserve their chemical structure during the laser deposition process. The CoPc optical signature is recognized in the ultraviolet–visible (UV–Vis) spectra of the obtained layers, these being dominated by the absorption bands associated to this organic compound while the ZnO optical fingerprint is identified in the photoluminescence spectra of the prepared layers, these disclosing the emission bands linked to this inorganic semiconductor. The hybrid nanocomposite layers exhibit globular morphology, which is typical for the thin films deposited by MAPLE. Current-voltage (J-V) characteristics of the structures developed on CoPc:C60:ZnO layers reveal that the addition of an appropriate amount of ZnO nanoparticles in the CoPc:C60 mixture leads to a more efficient charge transfer between the organic and inorganic components. Due to their photovoltaic effect, structures featuring such hybrid nanocomposite thin films deposited by MAPLE can have potential applications in the field of photovoltaic devices.
关键词： cobalt phthalocyanine,photovoltaic effect,hybrid nanocomposite films,MAPLE,ZnO nanoparticles
更新于2025-09-19 17:13:59
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Ferroelectric photovoltaic and flexoa??photovoltaic effects in (1a?? <i>x</i> )(Bi <sub/>0.5</sub> Na <sub/>0.5</sub> )TiO <sub/>3</sub> a?? <i>x</i> BiFeO <sub/>3</sub> systems under visible light
摘要： The anomalous photovoltaic (APV) effect has witnessed great progress from classical ferroelectric photovoltaics to flexo-photovoltaics. Both call for an extension of the spectral response range. Here, we present a comprehensive study on the ferroelectric, photoelectric, and photovoltaic properties of pure (Bi0.5Na0.5)TiO3 (BNT) and 0.3(Bi0.5Na0.5)TiO3-0.7BiFeO3 (0.3BNT-0.7BFO) ceramics. The data show that pure BNT with typical ferroelectricity exhibits intriguing photovoltaic effect even when illuminated by 550 nm visible light, while the 0.3BNT-0.7BFO solid solution with enhanced visible light absorption shows no ferroelectric photovoltaic due to the negligible ferroelectricity but striking strain-induced flexo-photovoltaic effect. Transmission electron microscopy analysis reveals distinctions in the domain structures and local strain states in pure BNT and 0.3BNT-0.7BFO ceramics, which may account for their differences in photovoltaic behavior. These findings not only deepen the understanding of photovoltaic mechanisms induced by ferroelectric polarization and flexoelectric effect but also highlight a possible candidate for multifunctional photoelectric applications.
关键词： BiFeO3,(Bi0.5Na0.5)TiO3,photovoltaic effect,visible light response
更新于2025-09-19 17:13:59
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Domain and Switching Control of the Bulk Photovoltaic Effect in Epitaxial BiFeO3 Thin Films
摘要： Absence of inversion symmetry is the underlying origin of ferroelectricity, piezoelectricity, and the bulk photovoltaic (BPV) effect, as a result of which they are inextricably linked. However, till now, only the piezoelectric effects (inverse) have been commonly utilized for probing ferroelectric characteristics such as domain arrangements and resultant polarization orientation. The bulk photovoltaic effect, despite sharing same relation with the symmetry as piezoelectricity, has been mostly perceived as an outcome of ferroelectricity and not as a possible analytical method. in this work, we investigate the development of BpV characteristics, i.e. amplitude and angular dependency of short-circuit current, as the ferroelastic domain arrangement is varied by applying electric fields in planar devices of Bifeo3 films. A rather sensitive co-dependency was observed from measurements on sample with ordered and disordered domain arrangements. Analysis of the photovoltaic response manifested in a mathematical model to estimate the proportion of switched and un-switched regions. the results unravel the potential utility of BPV effect to trace the orientation of the polarization vectors (direction and amplitude) in areas much larger than that can be accommodated in probe-based techniques.
关键词： BiFeO3,ferroelectricity,polarization orientation,domain switching,bulk photovoltaic effect
更新于2025-09-16 10:30:52
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Light-controlled molecular resistive switching ferroelectric heterojunction
摘要： Molecular ferroelectrics have attained significant advancement as a promising approach towards the development of next-generation non-volatile memory devices. Herein, the semiconducting-ferroelectric heterojunctions which is composed of molecular ferroelectrics (R)-((cid:1))-3-hydroxlyquinuclidinium chloride together with organic charge transfer complex is reported. The molecular ferroelectric domain provides polarization and bistability while organic charge transfer phase allows photo-induced charge generation and transport for photovoltaic effect. By switching the direction of the polarization in the ferroelectric phase, the heterojunction-based devices show non-volatile resistive switching under external electric field and photocurrent/voltage induced by light excitation, stable fatigue properties and long retention time. Overall, the photovoltaic controlled resistive switching provides a new route for all-organic multiphase non-volatile memories.
关键词： Molecular ferroelectrics,photovoltaic effect,heterojunctions,non-volatile memory,resistive switching
更新于2025-09-16 10:30:52
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3C-SiC/Si heterostructure: an excellent platform for position sensitive detectors based on photovoltaic effect
摘要： Single crystalline silicon carbide (3C-SiC) on Si-substrate has drawn significant attention in recent years due to its low wafer cost and excellent mechanical, chemical, and optoelectronic properties. However, the applications of the structure have primarily been focused on piezoresistive and pressure sensors, bio-mems, and photonics. Herein, we report another promising application of the heterostructure as a laser spot position sensitive detector based on the lateral photovoltaic effect (LPE) under nonuniform optical illuminations at zero-bias conditions. The LPE shows a linear dependency on spot positions and the sensitivity is found to be as high as 33 mV/mm under an illumination of 2.8 W/cm2 (635 nm). The structure also exhibits a linear dependency of LPE over a large distance (7 mm) between two electrodes, which is crucial for PSDs as the region with a linear dependency of LPE is only usable for PSDs. The LPE at different spot positions and under different illumination conditions have been investigated and explained based on the energy-band analysis. The temperature dependency of the LPE and position sensitivity are also investigated. Furthermore, the 2D-mapping of the lateral photovoltages reveals the potential for utilizing the 3C-SiC/Si heterostructure to detect the laser spot position precisely on a plane.
关键词： 3C-SiC/Si heterostructure,Lateral photovoltaic effect,position detector,energy-band analysis,harsh environments
更新于2025-09-16 10:30:52