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Sensitive, selective and rapid ammonia-sensing by gold nanoparticle-sensitized V2O5/CuWO4 heterojunctions for exhaled breath analysis
摘要： Marigold flower-like V2O5/CuWO4 heterojunctions were synthesized and its volatile organic compound (VOC)-sensing properties were tested and significantly enhanced after sensitizing by Au nanoparticles. Detailed characterizations were carried out by SEM, XRD and XPS to determine the morphology, crystal structure, elemental and chemical composition of the sensing materials, respectively. The fabricated gold-sensitized sensor was found to be rapidly responsive (a few seconds), highly sensitive to ammonia with good selectivity as compared to various types of VOCs. The limit of detection and linear range of sensor at 150°C were 212 ppb and 5-158 ppm, respectively, which is suitable for detection of exhaled breath ammonia of patients at their last stage of chronic kidney disease. Furthermore, it was found to be of high intra-day repeatability, which is properly explained by discussing the mechanism of NH3 sensing. Very long-term stability of the sensor was investigated over 56 days, once a week.
关键词： Ammonia-sensing,chronic kidney disease,exhaled breath analysis,Au-sensitized V2O5/CuWO4 heterojunctions
更新于2025-09-19 17:13:59
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Analysis of Processa??Dependent Electrical Properties of Silicon Heterojunction Solar Cells by Quantum Efficiency and Temperaturea??Dependent Current Densitya??Voltage Measurements
摘要： Amorphous silicon–crystalline silicon (a-Si:H/c-Si) heterojunction solar cells are fabricated by infrared (IR) radiative or resistive preheating of silicon wafers before the a-Si:H layers deposition. The cells with IR radiative or resistive preheating lead to without S-shape (WoS) or with S-shape (WS) in their light current density–voltage (J–V) characteristics, respectively. The Suns-Voc analysis shows no front/back metal contact barriers for minority carriers in both cells. The light- and voltage-bias-dependent quantum efficiencies of the WS cell show the hindrance of carrier collection at the a-Si:H/c-Si interface due to the band offset, whereas more defective a-Si:H layers are observed in the WoS cell. The WS and WoS cells’ temperature-dependent dark J–V characteristics reveal that the carrier transport is through tunnel-assisted recombination and tunneling, respectively. The IR preheating of wafers results in the reduction of the bandgap of a-Si:H and facilitates for minimizing the band offset at the interface, whereas, the resistive heating shows the relatively better a-Si:H/c-Si interface passivation.
关键词： S-shapes,heterojunctions,quantum efficiencies,amorphous silicon,band offsets,silicon solar cells
更新于2025-09-19 17:13:59
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Hydrogen‐Assisted Growth of Ultrathin Te Flakes with Giant Gate‐Dependent Photoresponse
摘要： Van der Waals (vdW)-integrated heterojunctions have been widely investigated in optoelectronics due to their superior photoelectric conversion capability. In this work, 0D bismuth quantum dots (Bi QDs)-decorated 1D tellurium nanotubes (Te NTs) vdW heterojunctions (Te@Bi vdWHs) are constructed by a facile bottom-up assembly process. Transient absorption spectroscopy suggests that Te@Bi vdWH is a promising candidate for new-generation optoelectronic devices with fast response properties. The subsequent experiments and density functional theory calculations demonstrate the vdW interaction between Te NTs and Bi QDs, as well as the enhanced optoelectronic characteristics owing to the plasma effects at the interface between Te NTs and Bi QDs. Moreover, Te@Bi vdWHs-based photodetectors show significantly improved photoresponse behavior in the ultraviolet region compared to pristine Te NTs or Bi QDs-based photodetectors. The proposed integration of vdWHs is expected to pave the way for constructing new nanoscale heterodevices.
关键词： bismuth quantum dots,plasma,heterojunctions,van der Waals,tellurium nanotubes
更新于2025-09-19 17:13:59
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Determination of Defect Densities in Thin (i) a‐Si:H Used as the Passivation Layer in a‐Si:H/c‐Si Heterojunction Solar Cells from Static Planar Conductance Measurements
摘要： A set of (p) a-Si:H/(i) a-Si:H/(n) c-Si heterostructures is investigated by coplanar conductance measurements. The thickness of the (i) a-Si:H buffer layer is varied between 2 and 50 nm, well beyond the values used in heterojunction solar cells. The change in this thickness plays a role on band bending at the heterointerface and therefore impacts the level of inversion of carrier population at the c-Si surface. Measurements are compared with 1D analytical calculations and 2D electrical modeling. It is demonstrated that the deep defect density, related to silicon dangling bonds, in the (i) a-Si:H layer strongly increases from 1 (cid:1) 1017 to (cid:3)3 when the (i) a-Si:H layer thickness is decreased from 50 to 2 nm. 4 (cid:1) 1018 cm This result is interpreted in terms of defect formation and dependence of the defect density upon the position of the Fermi level with respect to the valence band edge. Quantitative analysis in the framework of the defect-pool model demonstrates that the strong increase of defect density is also promoted by an increase in the width of the valence band tail in the thin (i) a-Si:H layer, suggesting that a very thin layer also suffers from increased disorder.
关键词： electrical modeling,passivating layers,coplanar conductance,a-Si:H/c-Si heterojunctions,dangling bonds
更新于2025-09-19 17:13:59
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Suppression of Parasitic Epitaxy Growth and Realization of High-Quality Wafer Surface Passivation of Silicon Heterojunction Solar Cells
摘要： Intrinsic hydrogenated amorphous silicon (i-a-Si:H) ?lms lead to excellent surface passivation of crystalline silicon wafers. However, a-Si:H deposition on a crystalline silicon wafer often results in undesired epitaxy growth, which deteriorates the passivation property, In this paper, we studied the in?uence of varying plasma enhanced chemical vapor deposition (PECVD) parameters, such as the product of the gas pressure (P ) and the electrode distance (Di) and the hydrogen dilution ratio (R = SiH4/(H2 + SiH4) × 100), on the passivation quality and the properties of silicon heterojunction (SHJ) solar cells. Measurements showed that proper combinations of high P ×Di and large R values can yield high minority carrier lifetimes (MCLTs) of passivated silicon wafers. Also, the tendency of MCLTs measured from passivated wafers is the same as that for open circuit voltages (Voc) of fabricated SHJ solar cells. A high Voc is obtained from SHJ solar cells when unwanted epitaxial growth is minimized at the wafer surface.
关键词： Plasma-enhanced chemical-vapor deposition,Amorphous semiconductors,Silicon solar cells,Heterojunctions
更新于2025-09-19 17:13:59
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Electronic and optoelectronic performance of nano-Vanadyl 2,3-naphthalocyanine/n-Si (organic/inorganic) solar cells: Temperature dependence
摘要： Vanadyl 2,3-naphthalocyanine (VONc) /n-Si heterojunction was prepared by vacuum deposition of VONc compound onto n-Si single crystals. The analysis of the X-ray diffraction pattern and the scanning electron microscopy images reveal the nanostructure nature of the deposited VONc film. At low voltage, the temperature dependence of current density-voltage characteristics corroborates that the multi-tunneling mechanism is the dominant current mechanism for the dark forward bias. In the case of the higher forward bias (0.4<V<2 V), the conduction mechanism is a space charge limited current dominated by a single trap level. The capacitance-voltage characteristics imply that the junction has an abrupt heterojunction description and the value of built-in voltages, at room temperature, was estimated to be 0.67 eV. The values of the open-circuit voltage, the short-circuit current, fill factor and power conversion efficiency under illumination (100 mW/cm2) and at room temperatures were calculated to be 0.70 V, 11.30 mA/cm2, 0.394 and 3.12 %, respectively. These results indicate that VONc/n-Si heterojunction is characterized by remarkable considerable photovoltaic properties comparing with the other organic/inorganic heterojunctions.
关键词： photovoltaic,nanostructure films,Heterojunctions,organic materials
更新于2025-09-19 17:13:59
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Electrochemical growth and characterization of Cu2O:Na/ZnO heterojunctions for solar cells applications
摘要： Cu2O:Na/ZnO/FTO heterojunctions were successfully prepared by a simple two-step electrodeposition method. The effects of the doping concentration of Na on the electronic, morphological, microstructural, optical and electrical properties of the nanostructures were investigated. The deposition was carried out at various concentrations of Na ions and constant bath temperature (70 C°). Cyclic voltammetry was utilized for the determination of the selective potential for electrodeposition of pure Cu2O. Mott-Schottky electrochemical impedance analysis showed p-type conductivity for the Cu2O layers and n-type conductivity for the ZnO films. X-ray diffraction analysis indicated that all doped and undoped Cu2O nanostructures have a polycrystalline nature with a highly cubic Cu2O (111) oriented crystallites and a hexagonal wurtzite structure of ZnO having (002) preferential orientations. Scanning electron microscopy and atomic force microscopy measurements point out the decrease of the grain size and the roughness of Cu2O:Nax/ZnO heterojunctions with the formation of typical (111) textured feature, through the contribution of Na doping. From UV-Vis spectra, a red-shift of the bandgap from 2.223 to 2.008 eV with an increase in the optical conductivity range up to 9 x 1014 cm-1 was noted by increasing the Na content. The current-voltage characteristics of p-Cu2O:Na/n-ZnO heterojunctions showed excellent rectifying behavior, achieving a high rectifying ratio of 3133%. Na doping has been demonstrated by a huge drop in the series resistance of Cu2O/ZnO heterojunctions besides a great improvement in both of the ideality factor and the threshold voltages as well as photoelectric responses. The highlighted results are attractive and suitable for photovoltaic applications.
关键词： Cu2O/ZnO heterojunctions,metal-oxide,I-V,electrodeposition,sodium doping
更新于2025-09-19 17:13:59
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Understanding Transport in Hole Contacts of Silicon Heterojunction Solar Cells by Simulating TLM Structures
摘要： Silicon heterojunction (SHJ) solar cell device structures use carrier-selective contacts that enable efficient collection of majority carriers while impeding the collection of minority carriers. However, these contacts can also be a source of resistive losses that degrade the performance of the solar cell. In this article, we evaluate the performance of the carrier-selective hole contact—hydrogenated amorphous silicon (a-Si:H)(i)/a-Si:H(p)/indium tin oxide (ITO)/Ag—by simulating transport in SHJ solar cell transfer length method structures. We study contact resistivity behavior by varying the a-Si:H(i) layer thickness, ITO(n+) and a-Si:H(p) layer doping, temperature, and interface defect density at the a-Si:H(i)/crystalline silicon (c-Si) interface. In particular, we consider the effect of ITO/a-Si:H(p) and the a-Si:H(i)/c-Si heterointerfaces on contact resistivity as they play a crucial role in modulating transport through the hole contact structure. Transport models such as band-to-band tunneling, and thermionic emission models were added to describe transport across the heterointerfaces. Until now, most simulation studies have treated the ITO as a Schottky contact; in this article, we treat the ITO as an n-type semiconductor. Our simulations match well with corresponding experiments conducted to determine contact resistivity. As the a-Si:H(i) layer thickness is increased from 4 to 16 nm, the simulated contact resistivity increases from 0.50 to 2.1 Ωcm2, which deviates a maximum of 8% from the experimental measurements. It should be noted that we calculate the contact resistivity for the entire hole contact stack, which takes into account transport across the a-Si:H(p)/c-Si and ITO/a-Si:H(p) heterointerface. Corresponding experiments on cell structures showed a fill factor degradation from 77% to 70%. Our simulations indicate that a highly doped n-type ITO layer facilitates tunneling at the ITO/a-Si:H(p) heterointerface, which leads to low contact resistivities.
关键词： contact resistance,simulation,silicon,heterojunctions,Amorphous semiconductors
更新于2025-09-16 10:30:52
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Plasmon Ag and CdS quantum dot co-decorated 3D hierarchical ball-flower-like Bi <sub/>5</sub> O <sub/>7</sub> I nanosheets as tandem heterojunctions for enhanced photothermal–photocatalytic performance
摘要： Plasmon Ag and CdS quantum dot co-decorated three-dimensional (3D) hierarchical ball-flower-like Bi5O7I nanosheets as tandem heterojunction photocatalysts are synthesized by oil bath, photoreduction and hydrothermal processes. The formation of a tandem heterojunction structure facilitates the migration and spatial separation of photogenerated electron–hole pairs. Plasmon Ag nanoparticles can generate hot electrons to enhance the photothermal performance due to the surface plasmon resonance (SPR) effect. The unique 3D hierarchical ball-flower-like Bi5O7I nanosheets can provide a number of surface active sites and allow incident light to be reflected multiple times within the Bi5O7I nanosheets, thus improving the light utilization. Under the protection of Bi5O7I nanosheets, CdS quantum dots which are deposited by a hydrothermal strategy can effectively avoid photocorrosion. In addition, the introduction of Ag nanoparticles and CdS quantum dots extends the photoresponse to the near infrared (NIR) region. The photocatalytic degradation rate of Bi5O7I/Ag/CdS composites with a CdS content of 5.76 wt% exhibits the best photocatalytic activity, which is several times higher than that of pristine Bi5O7I. The photocatalytic hydrogen evolution is about 10 times higher than that over Bi5O7I nanosheets. Moreover, the photothermal efficiency of Bi5O7I/Ag/CdS is also improved obviously. The results of cyclic experiments show that the composite photocatalysts have high stability. The outstanding photocatalytic and photothermal performance is attributed to the formation of tandem heterojunctions favoring the separation of charge carriers, the 3D hierarchical structure of Bi5O7I offering adequate surface active sites, and the SPR effect of Ag promoting the photothermal effect. These novel Bi5O7I/Ag/CdS tandem heterojunctions may provide a new insight into the synthesis of other photocatalysts with synergistic photocatalytic–photothermal effects.
关键词： tandem heterojunctions,photothermal–photocatalytic performance,Bi5O7I nanosheets,CdS quantum dot,Plasmon Ag
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