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A Type II n-n staggered orthorhombic V2O5/monoclinic clinobisvanite BiVO4 heterojunction photoanode for photoelectrochemical water oxidation: Fabrication, characterisation and experimental validation
摘要： Conventional photoanode using a singular semiconductor material is not technically viable for photoelectrochemical (PEC) water oxidation owing to the properties relating to its wide band gap, sluggish charge mobility, as well as poor separation and rapid recombination of photogenerated charge carriers. The main aim of this study was to fabricate an n-n heterojunction photoanode of V2O5/BiVO4 via a facile electrodeposition synthesis method in order to overcome the technical bottlenecks encountered in conventional singular photoanode structures. Additionally, the synergistic effect of band potentials matching and conductivity difference between BiVO4 and V2O5 were studied using LSV, IMPS, EIS, HR-TEM, XRD, XPS, Raman and ultraviolet-visible spectroscopies. This was followed by the performance evaluation of the light-induced water splitting using a standard three-electrode assembly PEC cell under 1.5 AM solar simulator. Results showed that the V2O5/BiVO4 heterojunction photoanode achieved a significantly improved photocurrent density of 1.53 mA/cm2 at 1.5 V vs Ag/AgCl, which was a 6.9-fold and a 7.3-fold improvement over the individual pristine BiVO4 (0.22 mA/cm2) and V2O5 (0.21 mA/cm2), respectively. The improvement was attributed to the lower charge resistances at the FTO/semiconductor, semiconductor/FTO and semiconductor/electrolyte interfaces as well as the fast transit time (τ) of 6.4 millisecond for photo-injected electrons in the V2O5/BiVO4 heterojunction photoanode. Finally, the experimental results were used to reconstruct a theoretical band diagram in validating the heterojunction alignment between V2O5 and BiVO4 as well as in elucidating the photogenerated charge carriers transfer mechanism in the V2O5/BiVO4 heterojunction photoanode.
关键词： Bismuth vanadate,n-n heterojunction,Charge separation,Photoelectrocatalysis
更新于2025-09-19 17:15:36
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[IEEE 2018 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) - Singapore (2018.7.16-2018.7.19)] 2018 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) - A Simple Method of Adjusting Trigger Voltage of HBT Device for ESD Protection
摘要： The trigger voltage of the HBT device is important for ESD protection. A method of adjusting the trigger voltage of SiGe Heterojunction Bipolar Transistor (HBT) device is proposed in this paper. The simulation and experiment results show that the trigger voltage of HBT can be simply adjusted by varying the emitter junction area.
关键词： Trigger voltage,Electrostatic discharge (ESD),Heterojunction bipolar transistor (HBT)
更新于2025-09-19 17:15:36
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Van der Waals broken-gap p-n heterojunction tunnel diode based on black phosphorus and rhenium disulfide
摘要： The broken-gap type-III van der Waals (vdW) heterojunction is of particular interest as there is no overlap between the energy bands of its two stacked materials. Despite several studies on straddling-gap (type-I) and staggered-gap (type-II) vdW heterojunctions, a comprehensive understanding of the current-transport and optoelectronic effects in a type-III broken-gap heterojunction remains elusive. Here, we report gate-tunable current rectifying characteristics in a black phosphorus (BP)/rhenium disulfide (ReS2) broken-gap p-n heterojunction diode. Current-transport in this heterojunction was modeled by using the Simmons approximation through direct tunneling and Fowler?Nordheim tunneling in low- and higher-bias regimes, respectively. We showed that a p-n diode based on a type-III heterojunction is mainly governed by tunneling-mediated transport, but that transport in a type-I p-n heterojunction is dominated by majority carrier diffusion in the higher-bias regime. Upon illumination with a 532-nm-wavelength laser, the BP/ReS2 broken-gap p-n heterojunction showed a photo responsivity of 8 mA/W at a laser power as high as 100 μW and photovoltaic energy conversion with an external peak quantum efficiency of 0.3%. Finally, we demonstrated a binary inverter consisting of BP p-channel and ReS2 n-channel thin film transistors for logic applications.
关键词： Rhenium disulfide,photovoltaics,quantum tunneling,broken-gap heterojunction,logic circuitry,Black phosphorous
更新于2025-09-19 17:15:36
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NO<sub>2</sub> gas sensing performance enhancement based on reduced graphene oxide decorated V<sub>2</sub>O<sub>5</sub> thin film
摘要： Here, we demonstrate the improved NO2 gas sensing properties based on reduced graphene oxide (rGO) decorated V2O5 thin film. Excluding the DC sputtered grown V2O5 thin film, rGO was spread over V2O5 thin film by drop cast method. The formation of several p-n heterojunctions is greatly affected by the current-voltage relation of rGO decorated V2O5 thin film due to p-type and n-type nature of rGO and V2O5, respectively. Initially with rGO decoration on V2O5 thin film, current decreases in comparison to V2O5 thin film, whereas depositing rGO film on glass substrate, current increases drastically. Among all sensors, only rGO decorated V2O5 sensor revealed maximum NO2 gas sensing response for 100 ppm at 150°C, and helped achieve approximately 61% times more response than the V2O5 sensor. An elaborated mechanism for an extremely high sensing response is attributed to the formation and modulation of p-n heterojunction at the interface of rGO and V2O5. In addition, the presence of active sites like oxygenous functional groups on rGO surface also enhances the sensing response. On that account, the sensor based on rGO decorated V2O5 thin film is highly suitable for the purpose of NO2 gas sensing. This enables timely detection of the gas, further prevent the ecosystem from its harmful effects.
关键词： NO2 gas,relative response,DC sputtering,p-n heterojunction,rGO decorated V2O5 thin film
更新于2025-09-19 17:15:36
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Direct Observation of Structure and Dynamics of Photogenerated Charge Carriers in Poly(3-hexylthiophene) Films by Femtosecond Time-Resolved Near-IR Inverse Raman Spectroscopy
摘要： The initial charge separation process of conjugated polymers is one of the key factors for understanding their conductivity. The structure of photogenerated transients in conjugated polymers can be observed by resonance Raman spectroscopy in the near-IR region because they exhibit characteristic low-energy transitions. Here, we investigate the structure and dynamics of photogenerated transients in a regioregular poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend film, as well as in a pristine P3HT film, using femtosecond time-resolved resonance inverse Raman spectroscopy in the near-IR region. The transient inverse Raman spectrum of the pristine P3HT film at 50 ps suggests coexistence of neutral and charged excitations, whereas that of the P3HT:PCBM blend film at 50 ps suggests formation of positive polarons with a different structure from those in an FeCl3-doped P3HT film. Time-resolved near-IR inverse Raman spectra of the blend film clearly show the absence of charge separation between P3HT and PCBM within the instrument response time of our spectrometer, while they indicate two independent pathways of the polaron formation with time constants of 0.3 and 10 ps.
关键词： polaron,femtosecond inverse Raman spectroscopy,conjugated polymer,bulk heterojunction
更新于2025-09-19 17:15:36
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Surface plasma Ag-decorated single-crystalline TiO2?x(B) nanorod/defect-rich g-C3N4 nanosheet ternary superstructure 3D heterojunctions as enhanced visible-light-driven photocatalyst
摘要： Ag-TiO2-x(B)/g-C3N4 ternary heterojunctions photocatalysts are fabricated by hydrothermal-calcination, photo-deposition procedure, and followed by in-situ solid-state chemical reduction procedure. As-obtained photocatalysts are consisted with heterojunctions between 2D g-C3N4 sheets and 1D TiO2(B) single-crystalline nanorods. The band gap of Ag-TiO2-x(B)/g-C3N4 ternary heterojunctions photocatalysts is reduced to ~2.23 eV due to plasma Ag and surface engineering. Under visible light irradiation, it has an optimal photocatalytic property for the reduction of Cr6+ (95%) and degradation of NH4+ (93%). The apparent reaction rate constants (k) of ternary heterojunctions photocatalysts for NH4+ and Cr6+ are 25 and 12 folds higher than that of original TiO2(B). Furthermore, Ag-TiO2-x(B)/g-C3N4 also has excellent hydrogen production efficiency, which is up to 410 mmol h-1 g-1. This enhancement can be attributed to the unique heterojunction formed by 1D single-crystalline TiO2(B) nanorods and 2D g-C3N4 sheets, surface plasma resonance effect of plasma Ag nanoparticle, and surface engineering. A possible photocatalytic mechanism is also proposed by analysizing the XPS valence-band spectra and the Mott-Schottky.
关键词： Surface engineering,g-C3N4 sheet,Visible-light-driven photocatalysis,Single-crystalline TiO2(B) nanorod,Heterojunction
更新于2025-09-19 17:15:36
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Multifunctional Optoelectronic Device Based on an Asymmetric Active Layer Structure
摘要： A single device with a variety of capabilities is highly attractive for the increasing demands of complex and multifunctional optoelectronics. A hybrid heterojunction formed between CsPbBr3 halide perovskite and chalcogenide quantum dots is demonstrated. The heterojunction served as an asymmetric active layer allows not only charge separation/exciton dissociation in a benign process, but also carrier injection/recombination with the suppression of bulk and interfacial nonradiative recombination. An individual device incorporating such a heterojunction is therefore implemented with an integration of proof-of-concept functions, including a voltage controllable multicolor light-emitting diode, an exceptionally high photovoltage energy-harvesting device, and an ultrafast photosensitive detector. The figures of merit of the light-emitting diode remarkably surpass those of the corresponding single-active-layer device, particularly in terms of its bright electroluminescence and superior long-term stability. The asymmetric active layer concept provides a feasible route to design efficient multifunctional and monofunctional devices in the future.
关键词： perovskite,asymmetric active layer,heterojunction,multifunctional optoelectronic device,multicolor electroluminescence
更新于2025-09-19 17:15:36
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Conformal Filling of TiO <sub/>2</sub> Nanotubes with Dense M <sub/>x</sub> S <sub/>y</sub> Films for 3D Heterojunctions: The Anion Effect
摘要： It is appealing to fill up TiO2 nanotube arrays with other semiconductors to form three-dimensional heterojunctions of interdigitated feature. This benefits from the large interfacial area for rapid charge separation and the ordered vertical channels for oriented charge transport. However, it remains a great challenge to fill the nanotubes with dense films and more importantly in a conformal manner. In this study, the TiO2 nanotubes are conformally filled with ZnS by successive ionic layer adsorption and reaction. The ZnS exists in the form of either discrete nanoparticles or dense films when using nitrate or acetate precursor solutions, respectively. This is attributed to the hydrolysis process of the acetates in aqueous solutions, which releases extra hydroxyl ions beneficial to film formation. The CuS/TiO2 heterojunctions, resulted from ZnS dense films, show better rectifying behaviors in view of the interdigitated structure. Such a conformal filling process with dense films can also be used to form other MxSy/TiO2 bulk heterojunctions toward applications in optoelectronics, photovoltaics, photocatalysis, and so on.
关键词： conformal coating,heterojunction,TiO2 nanotubes,Anodization,rectifying behavior
更新于2025-09-19 17:15:36
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Effect of electron radiation on electrical parameters of Zn/n-Si/Au–Sb and Zn/ZnO/n-Si/Au–Sb diodes
摘要： In this study, RF-magnetron sputtered ZnO thin film as an interlayer was used to improve radiation tolerance of the Schottky diodes. The structural and optical measurements showed that the ZnO thin films have hexagonal crystal structure with preferential c-axis orientation, 20.39 nm grain sizes and 3.15 eV bandgap. The electrical parameters such as ideality factor, barrier height and series resistance of Zn/n-Si/Au–Sb and Zn/ZnO/n-Si/Au–Sb diodes were calculated before and after electron radiation at 25, 50 and 75 gray doses. Deviation values of the parameters showed that the ZnO as an interlayer caused to improved radiation tolerance of the diodes.
关键词： Zinc oxide,Barrier height,Schottky diode,Electron radiation,Heterojunction
更新于2025-09-19 17:15:36
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Organic-inorganic nanoparticles molecularly imprinted photoelectrochemical sensor for α-Solanine based on p-Type Polymer Dots and n-CdS heterojunction
摘要： In this study, a molecularly imprinted polymer photoelectrochemcal (MIP-PEC) sensor based on semiconducting organic polymer dots (Pdots) and inorganic CdS quantum dots (QDs) has been established for the determination of α-Solanine. Specifically, p-type Pdots (p-Pdots) and n-type CdS QDs (n-CdS) were utilized to form organic-inorganic nanoparticles p-n heterojunction to enhance signal response, and their specific energy levels (VB/CB or HOMO/LUMO) were calculated for photoelectrochemical (PEC) bioanalysis application. At the same time, the combination of molecular imprinting technology and photoelectrochemistry overcomes the defeats of photoelectrochemistry which is the absence of selectivity, offers a new MIP-PEC sensor with high sensitivity and excellent selectivity based heterojunction enhanced strategy. In short, this study proposes the semiconducting organic-inorganic nanoparticles p-n heterojunction for molecularly imprinted polymer photoelectrochemcal bioanalysis application, and the MIP-PEC sensor was successfully fabricated based on these materials and methods. In the phosphate buffer solution (PBS), it was clearly observed that the photocurrent has a significant change between elution in acetic acid-ethanol mixture and incubation in template molecular solution because of the faster electron transfer speed, this phenomenon fully showed that the MIP-PEC sensor can specifically detect the target. Thus, the work typically offers a linear range from 0.01 to 1000 ng·mL?1 with a detection limit of 6.5 pg mL?1 for α-Solanine. Furthermore, the fabricated MIP-PEC sensor will confirm the actual application.
关键词： photoelectrochemical sensor,Molecularly imprinted polymer,p-n heterojunction,α-Solanine,organic-inorganic
更新于2025-09-19 17:15:36