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Significant Enhancement of Hole Transport Ability in Conjugated Polymer/Fullerene Bulk Heterojunction Microspheres
摘要： Bulk heterojunction (BHJ) strategy requires morphology of wide area donor-acceptor interfaces with high charge carrier mobilities through the bicontinuous charge transporting layers. Here, we report formation of well-defined bulk heterojunction (BHJ) microspheres from regiorandom poly(hexylthiophene) (rra-PHT)/phenyl-C61-butyric acid methyl ester (PCBM) mixture by a vapor diffusion method. By electrochemical oxidation, the BHJ microsphere exhibits enhanced generation of PHT cation species due to increased hole-transport property in comparison with a solution-cast film derived from rra-PHT/PCBM mixture without microsphere morphology. Photoconductivity and electrochemical stability of the microsphere are comparable or even higher than a cast film of irregular aggregates of regioregular P3HT.
关键词： polythiophene,bulk heterojunction,microspheres,electrochemistry,fullerene
更新于2025-09-23 15:22:29
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Different Types of Field-Effect Transistors - Theory and Applications || Quantum Confinement in High Electron Mobility Transistors
摘要： Modulation-doped semiconductor nanostructures exhibit extraordinary electrical and optical properties that are quantum mechanical in nature. The heart of such structures lies in the heterojunction of two epitaxially grown semiconductors with different band gaps. Quantum confinement in this heterojunction is a phenomenon that leads to the quantization of the conduction and the valence band into discrete subbands. The spacing between these quantized bands is a very important parameter that has been perfected over the years into device applications. Most of these devices form low-dimensional charge carriers that potentially allow optical transitions between the subbands in such nanostructures. The transition energy differences between the quantized bands/levels typically lie in the infrared or the terahertz region of the electromagnetic spectrum and can be designed according to the application in demand. Thus, a proper understanding and a suitable external control of such intersubband transitions (ISTs) are not only important aspects of fundamental research but also a necessity for optoelectronic device applications specifically towards closing the terahertz gap.
关键词： HEMT,intersubband transition,infrared,heterojunction,terahertz
更新于2025-09-23 15:22:29
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Noble-metal-free MOF derived hollow CdS/TiO2 decorated with NiS cocatalyst for efficient photocatalytic hydrogen evolution
摘要： Noble-metal-free hollow NiS/CdS/TiO2 (NS/CT) nanohybrid photocatalyst was prepared by a facile hydrolysis combining sulfidation process using metal-organic framework (MOF) as a template. The as-prepared composites were characterized by SEM, TEM, XRD, XPS, UV-vis, and photoelectrochemical techniques. It is found that NS/CT composites with porous hollow structure show significantly enhanced photocatalytic efficiency compare to TiO2, or CdS/TiO2, or even Pt decorated CdS/TiO2 photocatalysts, for hydrogen evolution from water upon visible light irradiation. Significantly, NS/CT composite with optimum amount of 30% CdS and 0.3% NiS exhibits the highest photoactivity, with H2 production rate of 2149.15 μmol·g-1·h-1, which is 23.9 and 2.3 times higher than that of the pure CdS particles and the CdS/TiO2 nanocomposites, respectively. The superiority of the composites arises from the synergistic effect of the heterojunction for rapid charge separation and the NiS cocatalyst for accelerated surface redox reaction.
关键词： NiS cocatalyst,H2 production,CdS/h-TiO2,heterojunction,photocatalysis.
更新于2025-09-23 15:22:29
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Analysis of current transport mechanisms in sol-gel grown Si/ZnO heterojunction diodes in high temperature environment
摘要： This paper analyzes the electrical parameters of Si/ZnO heterojunction diodes in the wide temperature range, i.e. from room temperature (298 K) to 573 K to study the electrical performance of the diode in very high temperature environment. In this work, sol-gel derived nanostructured ZnO thin film was deposited directly on p-Si substrate using spin coating technique. Electrical parameters, such as rectification ratio, reverse saturation current, ideality factor, barrier height, series resistance and activation energy are derived from current-voltage characteristics of the device, measured using semiconductor parameter analyzer in the temperature range of 298 K–573 K for bias voltage of ± 5 V. The ideality factor, barrier height and series resistance is derived as 2.66, 0.789 eV and 3554 Ω respectively at 298 K, whereas at 573 K these are modified as 1.58, 1.15 eV and 801 Ω respectively. The above-mentioned results indicate the presence of spatial barrier height inhomogeneities (BHI) in high temperature environment. Hence, we have included the Gaussian distribution of spatial BHI in our analysis to calculate the effective Richardson constant (RC). Before inclusion of spatial BHI, RC was 4.026 × 10^{-6} Acm^{-2}K^{-2}. However, after inclusion of spatial BHI, RC is modified to 29.14 Acm^{-2}K^{-2}, which is nearer to the theoretical value (32 Acm^{-2}K^{-2}). Therefore, this study indicates that our as-fabricated Si/ZnO heterojunction diodes can sustain their electrical behaviour in very high temperature environment also and they are suitable for high temperature electronic and optoelectronic application.
关键词： Current-voltage characteristics,Richardson constant,Trap-assisted tunneling,Spatial barrier inhomogeneities,Heterojunction diode,Semiconductor thin film
更新于2025-09-23 15:22:29
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In-situ ion exchange synthesis of Ag2S/AgVO3 graphene aerogels for enhancing photocatalytic antifouling efficiency
摘要： Efficient charge separation and cycle stability are critical for water purification by semiconductor photocatalyst. Herein, novel Ag2S/AgVO3 graphene aerogels (Ag2S/AgVO3@GAs) were synthesized via an in-situ ion exchange method. The series of characterization results verified that the Ag2S/AgVO3@GAs synergistically integrate the excellent properties of the Ag2S and AgVO3 into the macroscopic porous graphene aerogel. Furthermore, owing to the chelation of chitosan (CS) for AgVO3 and the ion exchange between well-dispersed AgVO3 and Na2S, the Ag2S can in situ grow on AgVO3, which prevents Ag2S and AgVO3 agglomeration/shedding in the photocatalytic reaction and contributes to the enhanced photocatalytic activity and cyclic stability. Benefiting from the unique structure, the Ag2S/AgVO3@GAs with excellent stability displayed the outstanding photodegradation efficiency for methyl orange (97% removal rate in 40 min) and disinfection activity for Escherichia coli (100% antibacterial efficiency in 36 min).
关键词： Photodegradation,Disinfection,Charge transfer,Three-dimensional graphene aerogel,Heterojunction
更新于2025-09-23 15:22:29
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Influence of Local Heterojunction on the Thermoelectric Properties of Mo-SnSe Multilayer Films Deposited by Magnetron Sputtering
摘要： Mo-SnSe multilayer films were deposited by multi-step magnetron sputtering. The Mo-SnSe multilayer films are then annealed, and the new phases including SnSe2 and MoSe2 are observed by x-ray diffraction and Raman spectroscopy. Scanning electron microscopy reveals that the SnSe exhibits the columnar grain structure with sizes from 50–100 nm. The high-resolution transmission electron microscopy shows the SnSe2 is dispersed at the boundary of the columnar grain and the local MoSe2/SnSe heterojunction is formed in the interior of the columnar grain. The influence of Mo content on the thermoelectric properties of SnSe thin films was investigated. A maximum power factor of 0.44 μW cm?1 K?2 was obtained for a 2.6 at.% Mo-doped SnSe thin film at 576 K, which is higher than that of a SnSe thin film deposited under the same conditions.
关键词： thermoelectric properties,heterojunction,SnSe films,sputtering
更新于2025-09-23 15:22:29
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Two-dimensional g-C3N4/TiO2 Nanocomposites as Vertical Z-scheme Heterojunction for Improved Photocatalytic Water Disinfection
摘要： Developing highly active photocatalysts towards effective microorganism inactivation is a green and energy-smart strategy in response to the growing demands to water quality under the background of the water crisis. Here, a vertical face-to-face heterojunction was fabricated by horizontally assembling TiO2 nanosheets with {001} facets exposed on graphitic carbon nitride (g-C3N4) sheets through a facile hydrothermal driving coupling. The vertical heterojunction could almost completely disinfect 103 CFU/mL E. coli within 30 min under solar light, which was more efficient than the physically mixed composite and pure g-C3N4 and TiO2. The two-dimensional (2D) morphology provides ample surface area in forming the vertical heterojunction and enables intimate contact which is advantageous to charge transfer between g-C3N4 and TiO2. A Z-scheme charge transportation mechanism is confirmed through band structure analysis and reactive species (RSs) probing and trapping experiments. In comparison with physically mixed composite and the single-phase counterparts, the nanocomposite based on Z-scheme electron transfer mode effectively prompts charge pair dissociation and subsequently encourages bacterial inactivation by boosting the generation of RSs. The constructing vertical Z-scheme heterojunction highlights the potential of 2D nanomaterials for accelerated water sterilization.
关键词： photocatalysis,Z-scheme heterojunction,vertical heterojunction,two-dimensional materials,water disinfection
更新于2025-09-23 15:21:21
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Theory-Driven Heterojunction Photocatalyst Design with Continuously Adjustable Band Gap Materials
摘要： The utilization efficiency of hot carriers in photocatalyst is limited at present by their fast recombination. Heterojunction interface would reduce the recombination rate by effectively facilitating spatial separation of the hot electron and hole. Here, we establish a heterojunction photocatalyst design principle by using continuously adjustable band gap materials. This is demonstrated using first-principles calculations, and is subsequently validated by direct measurements of photocatalytic activity of ZnxCd1-xS-reduced graphene oxide (RGO) heterojunction as a proof-of-concept photocatalyst. Tuning the Zn/Cd ratio and/or the reduction degree of RGO can result into three types of heterojunction, and different conduction and valence band offsets by varying their band gap and positions of band edges. The modulation of efficient electron-hole separation at the interface is manifested by the consistency of calculated and experimental optical absorbance, and enhanced photocatalytical activity of ZnxCd1-xS-RGO heterojunction. This results can also rationalize the available experimental results of RGO-based composites. This design principle is broadly applicable to the development of other heterojunction materials ranging from photocatalysts and solar cells to functional electronic devices through interfacial band alignment engineering.
关键词： band gap,photocatalytic activity,RGO,heterojunction,ZnxCd1-xS,photocatalyst,first-principles calculations
更新于2025-09-23 15:21:21
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Characteristics of GeSn-based multiple quantum well heterojunction phototransistors: a simulation-based analysis
摘要： Introduction of multiple quantum wells (MQWs) is an efficient way to enhance the light absorption capability in phototransistors. Direct band gap Ge1?xSnx alloy (x?>?0.08) having large absorption coefficient is an attractive material for heterojunction phototransistors (HPTs) compatible with CMOS platform. In this work, simulations are employed to obtain current gain, responsivity and collector current characteristics of Ge/GeSn/Ge HPTs with incorporation of MQWs (Ge0.87Sn0.13/Ge0.83Sn0.17) in the base region. The performances of bulk, single quantum well and MQW HPT structures are examined and compared. Best performance is shown by HPTs having MQW structure over a wide range of base emitter voltage.
关键词： simulation,current gain,heterojunction phototransistors,responsivity,GeSn,multiple quantum wells
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Thermo-enhanced field electron emission by bandto-ban tunneling from p-Si/ZnO nano-emitters
摘要： We fabricated full array of uniform individual p-Si/ZnO nano-emitters and demonstrated the strong thermo-enhanced field emission. The emission current density showed about ten-time enhancement (from 1.31 to 12.11 mA/cm2 at 60.6 MV/m) by increasing the temperature from 323 K to 623 K. The strong thermo-enhancement was proposed to be benefit from the increase of band-to-band tunneling probability at the surface portion of the p-Si/ZnO nano-junction. This work provides promising cathode for portable x-ray tubes/panel, ionization vacuum gauges and low energy electron beam lithography, in where electron-dose control at a fixed energy is needed.
关键词： p-Si/ZnO heterojunction,band-to-band tunneling,solution-phase growth,thermo-enhanced field emission,nano-template
更新于2025-09-23 15:21:21