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In this article, we introduce a double-gate nanotube tunneling field-effect transistor with high scalability based on the Si/Ge heterostructure. Our device includes two Ge source regions which are covered by the gate metal to facilitate line tunneling in these regions. The tunneling charge carriers flow toward the drain region through two n⁻ Si channel regions. The manufacturing process of the proposed transistor is fully compatible with CMOS technology. The performance of the device is investigated by employing a numerical simulator which is calibrated to experimental data. We achieved a remarkable switching performance including a minimum subthreshold swing (SS) of 10 mV/dec, an I $_{{on}}$ / I $_{{off}}$ ratio of 3.92 x 10⁷, an on-state current of 52.19 μA/μm, and a drain-induced barrier lowering of 45 mV/V for the device; moreover, the ambipolar conduction completely vanished.

The polycrystalline ceramic (Sm0.75Bi0.25FeO3)0.5 (BaTiO3)0.5 (SF-BT) is synthesized by high temperature solid state reaction method at an optimized temperature 1250 °C. The sample is investigated for its multifunctionality by analyzing its structural and electrical properties. The room temperature XRD pattern confirms the single phase compound in the tetragonal symmetry. The symmetry of the compound have been verified by commercially available software POWD. Complex impedance studies confirm the grain contribution to the electrical properties in the material. It reveals semiconducting behaviour of the material and transport phenomena is due to short range mobility of charge carriers. The relaxation mechanism in the sample is due to the short-range mobility of charge carriers.

Abundant heat is generated in household, industry and natural processes, and the majority of the heat is dissipated to environment as waste heat owing to the low heat utilization efficiency. Hence, to harvest waste heat is of great significance for the sustainable development. Among the heat-harvesting technologies including organic Rankine cycles, thermo-osmotic energy conversion and thermoelectric generators (TEGs), TEGs that can directly convert heat into electricity is the only feasible technology to harvest the low-grade heat that has a temperature below 200 oC and is about 2/3 of the total waste heat. The operational principle of TEGs is the Seebeck effect of electronic thermoelectric (TE) materials such as semiconductors or semimetals. Recently, ionic conductors, such as liquid ionic conductors and gel ionic conductors, emerged as the next-generation TE materials mainly due to their high thermopower. Their thermopower can be higher than that of the electronic TE materials by 2-3 orders in magnitude. In addition, they usually have a low thermal conductivity. Because the charge carriers in ionic conductors are cations and anions, the principle for the ionic thermopower and ionic TE conversion devices are notably different from the electronic counterparts. Very exciting progress has been made on the ionic TE materials and devices. This article provides a review on the ionic TE materials, including the thermopower mechanism, TE properties, and applications.

The photoelectrochemical (PEC) process is one of the most promising techniques for converting solar energy directly into clean fuels and for environmental remediation applications. One-dimensional (1D) TiO2 nanostructure arrays are extensively studied morphologies for a wide range of catalytic processes, including photocatalysis (PC) and PEC reactions for water splitting. In this study, a well-aligned spaced TiO2 nanorod (TNR) arrays were uniformly grown on a fluorine-doped tin oxide (FTO) substrate, and thermal exfoliation of the TNRs, which appeared as small islands, was investigated. The calcination time, which ranged from 1 to 5 h at 400 °C, had a significant impact on the agglomerated TNRs islands, which tended to be uniformly exfoliated as spaced nanorods and eventually improved the PEC performance. The regularly arranged spaced nanorods allow for the efficient transfer of internal charge carriers within the TNRs. Furthermore, the heterojunction formation with NiCo2S4 via the successive ionic layer adsorption and reaction (SILAR) method, substantially improve PEC performance, owing to reduced charge carrier recombination at the interface of the heterojunction. The Mott–Schottky analysis strongly supports the improved charge carrier density at the heterojunction interface. The improved life time of the charge carriers was investigated by comparing the time-resolved photoluminescence spectra for the TiO2/NiCo2S4 heterojunction with pristine TNRs, which was eventually confirmed by incident photon-to-current efficiency analysis.

Molecules of 12-o-carboranyldodecylphosphonic acid form a novel self-assembled monolayer (SAM) on alumina, which can effectively tune charge carriers in organic field effect transistors (OFETs) with the assembled dipoles of o-carborane at the semiconductor–dielectric interface. This SAM has not only realized p-channel OFETs of pentacene with both low threshold voltage and high field effect mobility (up to 5.2 cm2 V−1 s−1), but also enabled ambipolar charge transport in the solution-processed thin films of a chlorinated tetraazapentacene, which is a typical n-type organic semiconductor. As measured with Kelvin probe force microscopy, the SAM of CBPA has a surface electrostatic potential of −0.40 ± 0.10 V versus gold, which is in agreement with the observed shift of threshold voltage in the OFETs.

Chemical oxidative copolymerization has been employed for the synthesis of pyrrole and aniline copolymer at room temperature, in equal proportion. The prepared copolymer was undoped and then further doped with 10% NiCl2 using immersion method. Structural characterization of self-doped, undoped and doped copolymer was performed using FTIR, WAXD and SEM techniques. Results reveal the modifications in the original copolymer structure accompanied by various shifts in the band positions and appearance of the new bands in IR spectrum due to doping. The X-ray diffractograms reveals presence of modified and shifted peaks indicating the changes due to doping. The scanning electron micrographs of undoped and doped copolymers show globular structure due to doping when compared with that of the parent copolymer. In addition, using two probe methods the dc electrical conductivity of these samples was recorded in the temperature range of 313 K to 673 K, at a field of 27 V/cm. The log σ Versus 1/T plots of the self-doped and doped samples display the transformation of the sample at a given temperature from metallic to semi conducting and vice versa. The I-V plots for the self-doped and doped copolymer has also been plotted at a fixed temperature of 323 K which shows linear behavior of the samples. The conductivity measurements show reduction in conductivity of prepared samples thereby suggesting the presence of bipolarons as charge carrier. The results confirm the effect of doping on the copolymer properties.

Prompt recombination of photo-generated charges in semiconducting material strictly restrict photocatalytic process efficiency. Herein, coupling of CuxP nanoparticles and PbTiO3 nanoplates through inert atmosphere calcination process for outstanding H2 production has been reported. Uniform edging distribution of CuxP nanoparticles over PbTiO3 nanoplates; witnessed from TEM analysis revealed an intimate material contact for charge transportation to the active reaction sites of catalyst surface. Besides, junction interface between CuxP and PbTiO3 component; confirmed from XPS and Mott-Schottky analysis yield an amplified photo/electro-chemical and catalytic performance. A stronger photocurrent density via., H2O2 electron scavenger and larger photovoltage in junction material compared with PbTiO3 counterpart; follows higher surface charge transfer efficiency and slower potential decay with longer charge carriers lifetime simultaneously. The PbTiO3 nanoplates with an optimum amount of CuxP have achieved maximum H2 production attaining conversion efficiency of 9.72%. Consequently, a type-II energy band alignment mechanism has been proposed for enhanced H2 production.

Designing and constructing advanced heterojunction architectures are desirable for boosting CO2 photoreduction performance of semiconductor photocatalysts. Herein, we have prepared hierarchical ZnS@ZnIn2S4 core-shell cages with controlled particle sizes using sequential synthesis of Zeolitic imidazolate (ZIF-8) polyhedrons, ZnS cages, and ZnIn2S4 nanosheets on the ZnS polyhedron cages. ZIF-8 polyhedrons are firstly synthesized by a liquid-phase approach. The subsequent sulfidation of the ZIF-8 polyhedrons results in the formation of ZnS polyhedron cages, which act as substrates for fabricating ZnS@ZnIn2S4 core-shell cages by growing ZnIn2S4 nanosheets. The size of ZnS cages can be tuned to optimize CO2 photoreduction performance of hierarchical ZnS@ZnIn2S4 core-shell cages. The synergy of the unique hierarchical core-shell cage-like structure and heterojunction composition endows the hybrid catalyst high incident light utilization, abundant active sites, and effective separation of photoexcited charge carriers. Benefiting from these advantages, the optimized hierarchical ZnS@ZnIn2S4 core-shell cages exhibit enhanced performance for CO2 photoreduction with the CO yield of 87.43 μmol h−1g−1 and 84.3% selectivity, which are much superior to those of single ZnIn2S4 or ZnS. Upon Au decoration, the CO2 photoreduction performance of ZnS@ZnIn2S4 core-shell cages is further enhanced because of the Schottky junctions and surface plasmon resonance effect.

All-inorganic perovskite materials (Typically: CsPbI2Br) have attracted enormous attention due to their illustrious thermal stability and appropriate bandgap, and their use in perovskite solar cells (PSCs) has been extensively investigated. However, the inevitable defects of the perovskite layer, energy level mismatch between perovskite and carbon electrodes, and the phase instability of CsPbI2Br limit the power conversion efficiency (PCE) and stability of carbon-based CsPbI2Br PSCs. Herein, we demonstrate a simple and effective strategy for regulating energy level, inhibiting carrier recombination, and delaying the degradation of perovskite by modifying the surface of CsPbI2Br with a new type of 2D perovskite Cs2PtI6. The carbon-based CsPbI2Br PSCs achieve a higher PCE (13.69 %) than the control device (11.10 %). The excellent matching of the energy level and suppression of charge carrier recombination should be responsible for the improvement in efficiency. Furthermore, the excellent hydrophobic performance of Cs2PtI6 enhances the moisture resistance of the device. This study provides a potential strategy for improving the performance and stability of all-inorganic CsPbI2Br PSCs.

Multilayered structures with abundant interfaces are highly desired for reducing the thickness and improving electromagnetic (EM) attenuation ability. Herein, elaborately designed laminar Fe3O4/MXene nanosheets exhibit great potential as high-efficiency and lightweight absorbers due to heterogeneous structure coupled with intensive magnetic-dielectric synergistic effect. The MXene nanosheets with metallic conductivity not only serve as a supporter to carry the magnetic Fe3O4, but also provide massive interfaces to facilitate the transport of charge carriers. Hollow Fe3O4 microspheres were evenly dispersed without apparent agglomeration on the MXene surface, giving rise to largely enhanced consumption ability of –42.7 dB over a broad qualified bandwidth (5.7 GHz) at 2.5 mm. Besides, static density functional theory (DFT) method was introduced to shed light on the absorption mechanism by portraying the interaction between the Fe3O4 and MXene. This study provides a crucial strategy for designing magnetic-supported composites by means of a large family of MXenes as thin and lightweight EM absorbers.

Interface engineering is an effective way to improve efficiency and long-term stability of perovskite solar cells (PSCs). Herein, an ionic compound tetrabutylammonium hexafluorophosphate (TP6) is adopted to passivate surface defects of the perovskite film. It is found that TP6 effectively reduced the surface defects, especially at the grain boundaries where the defects are abundant. Meanwhile, the exposed long alkyl chains and fluorine atoms in the TP6 enhanced the moisture stability of the perovskite film due to its strong hydrophobicity. In addition, the driving force of charge carrier separation and transport is increased by enlarged built-in potential. Consequently, the power conversion efficiency (PCE) of PSCs is significantly improved from 20.59% to 22.41% by increased open-circuit voltage (Voc) and fill factor (FF). The unencapsulated device with TP6 treatment exhibits better stability than the control device, and the PCE retains ~ 80% of its initial PCE after 30 days under 15%–25% relative humidity in storage, while the PCE of the control device declines by more than 50%.

Nowadays solar cell is one of the best techniques for energy harvesting, we are using CH3NH3PbI3 perovskite material for solar cells applications. One of the most exciting developments in photovoltaics over recent years has been the emergence of perovskite (CH3NH3PbI3) as a promising new material for low-cost, high-efficiency photovoltaics. In this paper, we are assuming the layer of perovskite free from defects. A solar cell simulation software GPVDM, which works as a popular solar cell simulation tool (AMPS: Analysis of microelectronic and photonic structures) was used. The simulation model solves drift–diffusion of electron and hole, carrier continuity equations in position space to describe the movement of charge within the device, poison’s equation, and recombination of charge carriers.

Using natural mineral to realize photocatalytic reduction of CO2 is promising but remains a great challenge. Herein MoO3-x quantum dots (QDs) immobilized on acid modified palygorskite (H-Pal) nanocomposite was prepared as powder photocatalyst for CO2 conversion. The effect of various mass fractions of MoO3-x on CO2 reduction was investigated. Results reveal that the 30% MoO3-x/H-Pal demonstrates remarkable CO2 photoreduction property with a CH3OH yield rate of about 6.2 μmol·g−1·h−1 under full spectrum irradiation. The MoO3−x QDs possess high localized surface plasmon resonance (LSPR) effect induced by oxygen vacancy (Ov) not only enables the efficient capture of NIR photons, but also build S-scheme heterostructure with H-Pal mediated by Ov enhancing the separation of charge carriers as well as preserving high redox potential. In addition Ov act as active sites promoting the adsorption and activation of CO2. This work may provide a cost-effective strategy for the practical application of artificial photosynthesis.

Hierarchical structure Bi2MoxW1-xO6 (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) solid solutions with high surface area are prepared by hydrothermal method without employing any surfactant. All the as-prepared products are hierarchical microspheres self-assembled by nanosheets. The piezocatalytic performance of Bi2MoxW1-xO6 solid solutions are investigated by the degradation of RhB under ultrasonic vibration. The experimental results show that the x value of Bi2MoxW1-xO6 has great influence on the piezocatalytic efficiency. Among which, the Bi2Mo0.4W0.6O6 presents a high value of the rate constant k of 0.119 min-1 by degrading 97.5% of RhB dye solution in 30 min. It is about 43.4% higher than that of pure Bi2WO6 sample, for which k is 0.083 min-1. Radical trapping test indicates that holes (h+) are the dominating active species in the degradation process. The improved piezocatalytic performance for Bi2Mo0.4W0.6O6 sample ascribes to the larger piezoelectric potential generated under a strained state, which facilitates the transfer of charge carriers and accelerate the piezocatalytic process. Our work presents a new design strategy of piezocatalysts for remediation of water pollution.

The ferroelectric material In2Se3 is currently of significant interest due to its built-in polarisation characteristics that can significantly modulate its electronic properties. Here we employ density functional theory to determine the transport characteristics at the metal-semiconductor interface of the two-dimensional multiferroic In2Se3/Fe3GeTe2 heterojunction. We show a significant tuning of the Schottky barrier height as a result of the change in the intrinsic polarisation state of In2Se3: the switching in the electric polarization of In2Se3 results in the switching of the nature of the Schottky barrier, from being n-type to p-type, and is accompanied by a change in the spin polarization of the electrons. This switchable Schottky barrier structure can form an essential component in a two-dimensional field effect transistor that can be operated by switching the ferroelectric polarization, rather than by the application of strain or electric field. The band structure and density of state calculations show that Fe3GeTe2 lends its magnetic and metallic characteristics to the In2Se3 layer, making the In2Se3/Fe3GeTe2 heterojunction a potentially viable multiferroic candidate in nanoelectronic devices like field-effect transistors. Moreover, our findings reveal a transfer of charge carriers from the In2Se3 layer to the Fe3GeTe2 layer, resulting in the formation of an in-built electric field at the metal-semiconductor interface. Our work can substantially broaden the device potential of the In2Se3/Fe3GeTe2 heterojunction in future low-energy electronic devices.

One of the most effective option of photocatalysts for water splitting is doped strontium titanate, SrTiO3. It has a high rate of photo-generated charge transfer and limited photocatalytic activity for water splitting. The search of an appropriate photocatalyst having a high visible light absorption as well as fast charge transportation is extremely needed, however it is a difficult task. The structural, electronic and optical properties of sulfur-doped SrTiO3 and nitrogen-doped SrTiO3 are investigated using calculations based on density functional theory (DFT). According to the band structure calculations, the O-2p states represented the higher levels of the valence band of pure SrTiO3. When S and N atoms are introduced into the SrTiO3 structure on the O site, electronic structure findings indicate that doping the Sulfur (S) atoms reduced the band gap significantly, whereas doping of N atoms increased the bandgap of SrTiO3. According to our results, the N-doped SrTiO3 has a sufficient band gap of 2.03 eV, as well as suitable high visible light absorption and charge carrier transportation. The optical properties showed that N-doped SrTiO3 has good photosensitivity for visible light. In addition, we have found a significant impurity state that differs from O 2p-states, which can increase photocatalytic efficiency. The results of studies of electronic band structure showed that electron-hole transportation was well consistent with the experimental data. Thus, the N-doped SrTiO3 in this study is indeed an attractive candidate for hydrogen evolution throughout the visible light range, providing a logical base for the establishment of innovative photocatalysts.

Thermoelectric materials have been extensively studied for applications in solid-state power generation and cooling. Progress has been made over the past decade in multiple materials systems, hence, it becomes increasingly valuable to be able to analytically model the transport behavior to optimize materials and compare different systems. The well-known effective mass modeling approach is often used to fit the data to the form expected for a single, parabolic band, with charge carrier scattering dominated by acoustic phonons, i.e., deformation potential scattering. However, many high-performance thermoelectric materials benefit from having multiple bands (multi-valley) and many have non-parabolic bands or complex scattering. Understanding how these effects alter properties from that given by the effective mass model provides rational strategies for new materials. In this review, we discuss how this can be done in three strategies, the first is how to evaluate the influence of point defects on charge carrier mobilities as well as thermal conductivity. Established methods are also available for considering additional scattering mechanisms for phonons and electrons. We focus on how to determine the parameters used in modeling that require the least amount of fitting. We discuss the thermoelectric transport in two different types of materials: lead chalcogenides and half Heuslers. The second strategy involves systems with multiple sets of conduction or valence bands, which are not necessarily aligned. We discuss different conditions in hypothetical materials systems by considering quality factors for each set of bands. We then demonstrate how the lessons learned are reflected in real thermoelectric materials systems. The third strategy uses resonant dopants, and lead chalcogenides have become model systems. These dopants create a distortion in the density of states inherently the parabolic dispersion assumption can no longer be used. It is possible nonetheless, to quantitatively reproduce thermoelectric transport properties, providing insights on how to best utilize resonant dopants. Finally, we provide an outlook, identifying limitations and challenges to solve in order to model, and better yet, predict the thermoelectric performance of different materials.

A high-efficiency and easy-available approach was developed to obtain a ternary heterojunction composites with advanced hydrogen evolution reaction (HER) performance under visible light by water split. PdAg bimetallic nanoparticles make a close contact interface between g-C3N4(CN) and Zn0.5Cd0.5S(ZCS). Under visible light irradiation, CN and ZCS are both excited to generate electron-hole pairs, PdAg bimetallic nanoparticles act as a bridge between CN and ZCS. Not only can the photogenerated electrons from CN be captured, but they can also be quickly transferred to the surface of ZCS and participate in the photocatalytic reaction to release H2, and the recombination of charge carriers between the contact interface of ZCS and CN can be significantly inhibited. In addition, the thin CN layer reduces the photocorrosion of the ZCS and enhances the specific surface area of the composite material. After testing, the composite material with 30 wt% ZCS and 4 wt% PdAg demonstrates hydrogen evolution performance, up to 6250.7 μmol g−1h−1, which is 753 times the hydrogen evolution rate of single-component CN and 12.6 times of ZCS/CN. Compared with single-component and two-component photocatalysts, the ternary ZCS/PdAg/CN photocatalyst achieves significantly enhanced photocatalytic activity.

Despite the huge expansion of GO/rGO market, there is a clear lack of experimental studies on getting high quality, large scale GO and rGO nanosheets/thin films, which is a critical requirement for electronic applications. In this work, a detailed experimental study on the effect of lateral sheet size on properties of GO/rGO, supported by density functional theory (DFT) calculations, is presented for the first time, to help prepare pristine graphene-like rGO. Furthermore, we investigated the effect of thermal reduction at low temperature (200 °C), under ambient pressure, on the corresponding electronic properties of rGO. Current-voltage (I–V) analysis, optical and electron microscopy, atomic force microscopy, Raman, XPS, and quantitative 13C NMR spectroscopy were used to study and optimize rGO. The optimized rGO-field-effect transistor (rGO-FET) device exhibited the highest charge carrier mobilities, i.e. 2,962 (holes) and 2,183 (electrons) cm [2]/V.s. Furthermore, the transconductance characteristics curve of rGO-FET showed the ambipolar behavior of high-quality graphene, with Dirac point around zero. In addition, the optical band gap of rGO nanosheets (∼0.4 eV), prepared in this work, is among the smallest reported band gaps for rGO. These findings highlight the significance of our study for synthesizing large-scale graphene-like rGO thin film, for ultra-fast, low-power transistor applications.

Despite the remarkable progress achieved in the field of non-fullerene acceptor (NFA)-based organic photovoltaics (OPVs) in recent years, the large energy loss remains the major factor limiting the power conversion efficiency (PCE) of in OPVs. Although many studies on polymer OPVs have been reported, low energy loss systems with high efficiency are rarely reported all-small-molecule organic-solar-cells (ASM-OSCs). This is partially because low energetic offset between donors and acceptors is usually required to get small energy loss, which could result in insufficient exciton dissociation driving force, making the trade-off between device performance and energy loss an important research focus. In this article, we reported ASM-OSCs based on three small molecule donors ZR1-C2, ZR1-C3 and ZR1-C4 with small molecule NFAs BTP-C11-N2Cl, BTP-C9-N2F and BTP-C9-N4F. Charge carrier mobilities, exciton dissociation efficiency and charge collection efficiency were measured and calculated for blends ZR1-C3:TP-C11-N4Cl, ZR1-C3:BTP-C9-N2F and ZR1-C3:BTP-C9-N4F, revealing good charge transport property. Morphology characterizations such as AFM, TEM and GIWAXS have been conducted, demonstrating excellent molecular compatibility, suitable phase separation with fibrous structures that provides efficient charge transport channels. By morphology and charge carrier optimization, the highest PCE of 14.29% was achieved with a small nonradiative energy loss of 0.2 eV which, to the best of our knowledge, is the highest PCE value for ASM-OSCs with non-radiative voltage loss ≤ 0.2 eV, reaching a balance between high performance and low energy loss.

The design and scale-up of carbon nanotube (CNT)-based thermoelectric (TE) modules is limited by the low structural similarity between p-type enhancers and n-dopants. This study was aimed at investigating the organic TE properties of polyazacycloalkane/CNT TE films prepared using the drop casting method and the effect of Cu ion doping that can coordinate with its organic ligands. The Seebeck coefficient of cyclen-doped CNTs was −43.3 μV K−1 at 345 K but reduced to 41.6 μV K−1 after adding Cu ions. Cu ion addition switched the charge carrier type of the composite film from electrons to holes owing to cyclen complexation with Cu ions, resulting in a neutral molecular state with suppressed electron donation of the dopant molecules. Notably, conventional approaches cannot maintain sufficient power characteristics owing to the reduced electrical conduction induced by structural defects in the nanotubes. However, herein, an output power exceeding 200 μW m−1 K−2 was obtained, which was 2–5 times higher than that of existing carrier-switchable CNTs. For a typical TE module consisting of five pairs of p-type (Cu(II)-cyclen/CNT)-n-type (cyclen/CNT) junctions, the generated TE voltage and power, depending on the temperature gradient, were similar to the theoretical values. Under optimized conditions, a maximum output power of 1.36 μW was achieved at a temperature difference of 75 K, which is higher than that of previously reported carrier-switchable CNT-based TE modules that used oil-based dopants, whereas we used optimal water-soluble dopants. The proposed approach can help simplify the path from material preparation to module fabrication.

Quantum confinement of the charge carriers of graphene is an effective way to engineer its properties. This is commonly realized through physical edges that are associated with the deterioration of mobility and strong suppression of plasmon resonances. Here, we demonstrate a simple, large-area, edge-free nanostructuring technique, based on amplifying random nanoscale structural corrugations to a level where they efficiently confine charge carriers, without inducing significant inter-valley scattering. This soft confinement allows the low-loss lateral ultra-confinement of graphene plasmons, scaling up their resonance frequency from the native terahertz to the commercially relevant visible range. Visible graphene plasmons localized into nanocorrugations mediate much stronger light–matter interactions (Raman enhancement) than previously achieved with graphene, enabling the detection of specific molecules from femtomolar solutions or ambient air. Moreover, nanocorrugated graphene sheets also support propagating visible plasmon modes, as revealed by scanning near-field optical microscopy observation of their interference patterns. A scalable soft nanoengineering technique enables the realization of visible plasmons in corrugated graphene.

Multiwall carbon nanotubes (MWCNTs) modified n- type Ni:Bismuth Vanadate photoanode has been prepared and investigated for solar energy induced water splitting for hydrogen generation. 0.5 wt% MWCNTs modified Ni:BiVO4 (M3) sample displayed the best response in comparison to the other samples. Electrochemical impedance spectroscopy (EIS) analysis indicates reduced charge transfer resistance and enhanced photoresponse at electrode/electrolyte interface. The calculated flat band potential, photocurrent density and applied bias photon to current conversion efficiency also support the augmentation in photoresponse. Thus, characteristics of MWCNTs has been demonstrated clearly which would support PEC efficiency as well as separation of charge carriers.

New ternary PVA/POPDA-GO-ZnO nanocomposite has been synthesized for electrical applications, using several facile synthesis-steps. X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared (FT-IR) used to characterize the structural properties, and the capacitance data to determine the dielectric constant (ɛ'), dissipation factor (ɛ''), and A.C. electrical conductivity (σa.c) in the frequency range (1 – 5 MHz). The structural exams proved the formation of crystalline ternary PVA/POPDA-GO-ZnO nanocomposite. The prepared PVA/POPDA-GO-ZnO film shows an enhanced electrical properties comparing with PVA film, the highest dielectric constant (ɛ') and A.C. electrical conductivity (σa.c) recorded to the ternary PVA/POPDA-GO-ZnO nanocomposite (1.62348), (3.29*10-5 S/m) at the frequency (1 MHz) and (5 MHz) respectively, while at the frequency (5 MHz) achieved the lowest dissipation factor (ɛ'') (0.46369). This improvement is due to the GO nanosheets and ZnO nanoparticles which effectively enhancing the transfer ability of charge carriers and the surface area of the ternary nanocomposite, the adding of crystalline POPDA polymer improves the electrical conductivity of the PVA matrix polymer. The electrical properties effectively depend on the frequency of applied electric field.

A series of novel three-dimensional (3D) CoTiO3/BiOBr (CTBB) hierarchical heterostructures were prepared via a simple hydrothermal method. In comparison with pure CoTiO3 and BiOBr, all the CTBB nanocomposites display enhanced photocatalytic performance toward dyes decomposition. Particularly, the CTBB-5 reveals the best photocatalytic efficiency for RhB removal with K of 0.2030 min-1, which is about 50.75 and 3.02-fold higher than pure CoTiO3 and BiOBr, respectively. The outstanding activity is further demonstrated by MO photodegradation. The dramatically enhanced activity can be accredited to the increased surface area and reduced recombination probability of charge carriers. Furthermore, CTBB-5 exhibits excellent stability after repetitively running four times. The h+ and •O2- are identified as the dominating reactive species contributing to the oxidation reaction. Finally, a possible Z-scheme charge transfer mechanism is presented and analyzed in detail.

Rechargeable aluminium-ion batteries (AIBs) are considered to be promising alternatives for current lithium-ion batteries (LIBs), since they can offer the possibilities of low cost with high energy-to-price ratios. Unlike in LIBs, the charge storage mechanism in AIBs involving different ionic species is far more complicated and remains largely unexplored, which impedes further screening and optimization of cathodes materials that can reversibly accommodate aluminium-based (complex) charge carriers with boosted cell performance. Here, we report a comprehensive study of the battery chemistry in metal selenide based cathode in AIBs from an integrated chemical and physical point of view. Various in situ and ex situ characterization techniques and theoretical calculations reveal that both Cl- and AlCl4- can act as the charge carriers in the FeSe2 cathode during the charge process, and the Al3+ can also be embedded into the host upon discharge process. Furthermore, using in situ magnetometry, the spin-polarized surface capacitance is observed in AIBs for the first time, which proves that Al3+ can serve as charge compensation in the formation of space charge zones with electrons. These innovative findings provide unprecedented insight into the charge storage mechanism of AIBs.

A Z-scheme photosystems combining Schottky junction and loading of applicable bandgap semiconductor is beneficial for enhancing the charge carriers' separation/transfer as well as maintain their excellent redox ability. Here, CdxZn1-xS@Au was in-situ deposited on the (010) facets of BiVO4 taking Au as a bridge for constructing a sandwich structure CdxZn1-xS@Au/BiVO4 Z-scheme photocatalyst. The electrons in BiVO4 (010) migrate unidirectionally to Au nanoparticles across the Schottky junction and effectively suppress opposite electrons flow, then be captured by the excited holes in CdxZn1-xS. Furthermore, Zn-doping also contributes to an appropriate redox ability and charge carriers separation. Benefiting from the dual-facilitated effects, the ternary CdxZn1-xS@Au/BiVO4 exhibited superior photocatalytic activity for CO2 reduction under visible light irradiation using H2O as a reducing agent, as compared with CdS and CdS@Au/BiVO4. Furthermore, the intermediate product HCOO* fixed on the surface of CdxZn1-xS@Au/BiVO4 is identified by in-situ FT-IR, playing a key role in the conversion of CO2 to CO and then improve photocatalytic selectivity.

Ag3PO4-based photocatalysts have been deeply studied in environmental remediation; however, two problems limited their further application: photocorrosion and quenching effect by in-situ generated H2O2. To addressed these two questions simultaneously, Fe2(MoO4)3 was coupled with Ag3PO4 to construct Z-scheme Fe2(MoO4)3/Ag/Ag3PO4 heterojunction driven by internal-electric-field. The rhodamine B degradation rate of heterojunction was 254 and 7.0 times higher than those of Fe2(MoO4)3 and Ag3PO4, respectively. The outstanding photoactivity was due to the high visible-light harvest, low interface resistance, high separation efficiency of charge carriers, long lifetime of hole (h+) and electron (e-), well-preserved oxidation potential of h+, and especially photocatalytic produced H2O2 inside the system. The in-situ generated H2O2 was fully activated to be •OH on the Fe2(MoO4)3 surface via a Fenton reaction, leading to the elimination of quenching effect on h+ and e-, and generation of more •OH. Additionally, in Z-scheme heterojunction, e- transferred from Ag3PO4 to Fe2(MoO4)3, avoiding the accumulation on Ag3PO4 surface, and hence suppressing the photocorrosion. As a result, 91.2% of degradation efficiency remained after 5 cycles. This paper provides a new method to simultaneously increase the degradation rate by utilizing the in-situ generated H2O2 and improve the stability of Ag3PO4 via constructing a Z-scheme heterojunction.

In this communication, we report the results of the studies on structural and transport properties of monovalent Na + doped La1-xNaxMnO3 (LNMO; x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) manganites synthesized by conventional ceramic method. X-ray diffraction (XRD) and Rietveld refinements reveal the single phasic nature of LNMO manganites without any detectable impurity within the measurement range. Temperature dependent resistivity, under different applied magnetic fields, has been performed on LNMO samples. Samples understudy exhibit metal to insulator (semiconductor) transition at temperature TP which is strongly influenced by the substitution of Na + at La 3+ site.  - T plots also exhibit resistivity upturn behavior at low temperature well below 40K under all the applied fields. Variation in TP and resistivity has been discussed in the context of the competition between the transport favoring tolerance factor and zener double exchange (ZDE) mechanism and transport degrading Jahn-Teller (JT) and size variance effects. In order to understand the mechanisms responsible for the charge transport in metallic and semiconducting regions and to explore the possible electronic processes responsible for the observed low temperature resistivity minima in all the presently studied LNMO manganites, various models have been employed. It has been found that VRH mechanism gets successfully fitted to the resistivity data in the semiconducting region while ZDE polynomial law is responsible for the charge conduction in metallic region for all the presently studied LNMO samples. A strong dependence of activation energy on the Na + - content as well as applied magnetic field has been discussed in the context of variation and interrelations between the structural parameters. Charge conduction in metallic region has been discussed in the light of electron-phonon interactions which is influenced by the Na + - content and applied magnetic field. Electrostatic blockade model has been employed to understand the low temperature resistivity minima behavior. Blocking energy for the charge carriers shows a dependence on the magnetic energy provided to the charge carriers. Present study can be useful to understand and to control the charge conduction in the manganites and hence to design the manganite based thin film devices for various spintronic applications. Copyright © 2016 VBRI Press.

Perovskite quantum dots (PQDs) have many properties that make them attractive for optoelectronic applications, including expanded compositional tunability and crystallographic stabilization. While they have not achieved the same photovoltaic (PV) efficiencies of top-performing perovskite thin films, they do reproducibly show high open circuit voltage (VOC) in comparison. Further understanding of the VOC attainable in PQDs as a function of surface passivation, contact layers, and PQD composition will further progress the field and may lend useful lessons for non-QD perovskite solar cells. Here, we use photoluminescence-based spectroscopic techniques to understand and identify the governing physics of the VOC in CsPbI3 PQDs. In particular, we probe the effect of the ligand exchange and contact interfaces on the VOC and free charge carrier concentration. The free charge carrier concentration is orders of magnitude higher than in typical perovskite thin films and could be tunable through ligand chemistry. Tuning the PQD A-site cation composition via replacement of Cs+ with FA+ maintains the background carrier concentration but reduces the trap density by up to a factor of 40, reducing the VOC deficit. These results dictate how to improve PQD optoelectronic properties and PV device performance and explain the reduced interfacial recombination observed by coupling PQDs with thin-film perovskites for a hybrid absorber layer.

This work synthesized a novel CuS/KTa0.75Nb0.25O3 (KTN) heterojunction composite and firstly applied it in photocatalytic and piezocatalytic reduction of N2 to NH3. XRD, Raman, XPS, SEM, and TEM analyses indicate that CuS nanoparticles closely adhered to the surface of KTN nanorods, which facilitates the migration of electrons between the two semiconductors. Mott-Schottky and valence band XPS analysis shows that KNbO3 shows a higher conduction band than CuS, indicating that CuS mainly acts as electron trappers to capture the photogenerated electrons from KTN. Because of the great enhanced spatial separation of photogenerated charge carriers, the CuS/KTN presents much higher performance than pure KNT, which is further confirmed by 1H NMR analysis of the reaction solution. An interesting finding is that synthesized CuS/KTN not only performs well under light irradiation but also can work in an ultrasonic bath, indicating its great potential in photo/piezocatalytic conversion of N2 to NH3. The optimal 10 %CuS/KTN shows an NH3 production rate of 36.2 μmol L−1 g−1 h−1 under ultrasonic vibration, which reaches 7.4 times that of KTN. The electrons generated by KTN through the piezoelectric effect can be captured by CuS, which endows the electrons a longer life to participate in the reaction, thereby improving the catalytic reaction performance.

Theory of spin noise in low dimensional systems and bulk semiconductors is reviewed. Spin noise is usually detected by optical means, continuously measuring the rotation angle of the polarization plane of the probe beam passing through the sample. Spin noise spectra yield rich information about the spin properties of the system including, for example, $g$-factors of the charge carriers, spin relaxation times, parameters of the hyperfine interaction, spin-orbit interaction constants, frequencies and widths of the optical resonances. The review describes basic models of spin noise, methods of its theoretical description, and their relation with the experimental results. We also discuss the relation between the spin noise spectroscopy, the strong and weak quantum measurements and the spin flip Raman scattering, and analyze similar effects including manifestations of the charge, current and valley polarization fluctuations in the optical response. Possible directions for further development of the spin noise spectroscopy are outlined., Comment: Accepted to Phys. Usp. The original manuscript in Russian is available in the supplementary files at arXiv and at this URL: https://www.dropbox.com/s/kz5uyz3btgocf8l/UFN_spin_noise_review_rus.pdf?dl=1

Herein, we report a reproducible improvement of the thermoelectric performance in BiSbTe alloy via kinetically and dynamically regulating excitation behavior in the intrinsic excitation regime. Doping with Pb increases the carrier concentration to the optimal value, kinetically pushing the onset temperature for the intrinsic excitation from 350 K for Bi0.46Sb1.54Te3 sample to 450 K for Pb0.01(Bi0.46Sb1.54)0.995Te3 sample. Moreover, the refined grains, nanostructures as well as dense dislocations induced by the melt-spinning process not only lower the lattice thermal conductivity via intensifying the interfacial phonon scattering but also selectively block the migration of minority carrier, modifying the dynamic process of the charge carrier and resulting in a smaller ratio of ( μ e / μ h ). This improves the power factor in the measured temperature range and suppresses the bipolar thermal conductivity in the intrinsic excitation regime. Thus, a maximum power factor of 4.44 mW m−1 K−2 and the lowest thermal conductivity of 1.06 W m−1 K−1 are attained for the sample with refined grains and nanostructures. All these contribute to the highest ZT value of 1.31 at 380 K and the highest average ZT value of 1.17 from 300 K to 500 K for Pb0.002(Bi0.46Sb1.54)0.999Te3 sample. This improved thermoelectric property was further verified in a thermoelectric module with the conversion efficiency of 4.38 % under a temperature gradient of 175 K, which is 20 % higher than that of the commercial ZM-based module under the same temperature gradient.

New, more stringent environmental requirements for electrical insulation liquids have led to the development of novel, more environment‐friendly liquid dielectrics. Ester fluids, introduced several decades ago, provide a viable alternative to traditional mineral insulating liquids. In order to expand the practical applications of these novel dielectric fluids, their dielectric and electrical parameters should be established. One of the critical parameters that affects and governs the development of pre‐breakdown processes in insulating liquids is the mobility of charge carriers. In the present paper, the mobility of charge carriers in commercially available synthetic and natural insulating ester fluids and in a mineral insulating oil were obtained using two methods, the time of flight and the space charge saturation current methods. The mobility was obtained for a wide range of electrical field magnitudes. It was found that the mobility of charge carriers is greater in the mineral oil than in both, the natural and synthetic, ester fluids. It was also established that the mobility is higher for higher applied electric field. The results of this work will help in characterizing liquid dielectrics and in optimizing high‐voltage systems in which liquid dielectrics, including natural and synthetic ester fluids, are used.

We report an investigation into the impact of applying a large reverse bias voltage during current–voltage (J-V) sweeps on the degradation rate of solar cells based on poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) and [6-6]-phenyl C71-butyric acid methyl ester (PC70BM), under air mass 1.5 simulated solar irradiation. The degradation rate was found to be significantly slower when devices were characterized using frequent J-V sweeps with a large reverse bias component (-7 V to 1 V), with a decrease in power conversion efficiency of 24% after ∼ 100 hrs of light exposure. In contrast, devices scanned from −1 V to 1 V degrade by 72% in the same time period. The decay in the photovoltaic performance was found to be related to an increase in the series resistance and a decrease in the shunt resistance of the devices over time. Further characterization of the bulk heterojunction layer under irradiation conditions indicates that this behavior might be caused by the decreasing mobility of the charge carriers due to the formation of the defects or traps in the layer, induced by the photo-oxidation process. The frequent application of a large reverse bias sweep most likely helps de-trap the charge carriers and slows down the device degradation. Impedance analysis indicated that during the decay of PCDTBT:PC70BM devices the bulk layer became more resistive with time, and applying large and frequent reverse bias sweeps during testing could significantly slow down this process. The charge carrier extraction time was found to increase from 7 μs to more than 400 μs after photo-degradation. These findings demonstrate that repeated application of a reverse bias voltage can affect device degradation, and therefore that the specific details of J-V characterization should be reported alongside device lifetime claims.

In this study, bromide-iodide lead perovskite (CH3NH3Pb(I1−xBrx)3) thin films were fabricated and applied as copper-free back contact layers for CdTe solar cells. The results reveal that the open-circuit voltage (Voc) and fill factor (FF) of the CdTe solar cells are greatly enhanced by the utilization of perovskite back contact layers. This is mainly due to the evidently reduced charge transportation barrier at the back contact, which is verified by temperature-dependent current–voltage (J-V-T) and apparent quantum efficiency (AQE) measurements. Specifically, after the application of perovskite back contact layer, the best-performing device shows 15.80% improvement in efficiency (from 10.82 to 12.53%), with Voc and FF increasing by 3.94% and 6.91%, respectively. Besides, the overall uniformity of the solar cells is also improved by the perovskite back contact, suggested by laser beam induced current (LBIC) results. Further simulation results confirm the experimental results and clarify the optimized cell performance by perovskite back contact layer in terms of both energy band alignment and charge carriers’ recombination. In addition, in the simulation section, we have also investigated the effect of the bandgap, thickness and doping level of perovskite and the doping level of CdTe on the cell performances. The experiments and the numerical simulation reported in this work suggest perovskite a potential copper-free back contact layer for the fabrication of efficient CdTe solar cells.

Transition metal chalcogenides quantum dots (TMCs QDs) demonstrate emerging potential in solar energy conversion owing to marvelous physicochemical properties, such as quantum size effect, large extinction coefficient, and multiple excitons generation. Nevertheless, TMCs QDs as photosensitizers are unstable owing to high surface energy, and moreover, substantial trap states of TMCs QDs annihilate the photo-induced charge carriers, thus resulting in ultra-short charge lifetime and inferior photoactivities. Herein, 0D/2D TMCs QDs/MXene heterostructures were designed by a ligand-initiated electrostatic self-assembly strategy, wherein positively charged TMCs QDs were anchored on the negatively charged ultrathin Ti 3C2Tx nanosheets (NSs) framework, which promotes the anisotropic unidirectional electron transport from TMCs QDs to MXene NSs. MXene functions as an effective charge mediator to decrease the charge recombination and prolong the charge lifetime for photocatalytic hydrogen generation and anaerobic reduction of nitroaromatics to amino compounds under visible light irradiation. Our work would shed new insights on the role of MXene in tuning the directional charge transport for solar energy conversion.

As a prospective visible-light-responsive photochemical material, graphitic carbon nitride (g-C3N4) has become a burgeoning research hot topics and aroused a wide interest as a metal-free semiconductor in the area of energy utilization and conversion, environmental protection due to its unique properties, such as facile synthesis, high physicochemical stability, excellent electronic band structure, and sustainability. However, the shortcomings of high recombination rate of charge carriers, relatively low electrical conductivity and visible light absorption impede its practical application. Various strategies, such as surface photosensitization, heteroatom deposition, semiconductor hybridization, etc., have been applied to overcome the barriers. Among all the strategies, functional nanocarbon materials with various dimensions (0D∼3D) attract much attention as modifiers of g-C3N4 due to their unique electronic properties, optical properties, and easy functionalization. More importantly, the properties of these functional nanocarbon materials can be tuned by various dimensions and thus there will be a way to overcome the defects of g-C3N4 by choosing different dimensional carbon materials. Distinguishing from some present reviews, this review starts with the fundamental physicochemical characteristics of g-C3N4 materials, followed by analyzing the advantages of functional nanocarbon materials modifying g-C3N4. Then, we present a systematic introduction to various dimensional carbon materials.The design philosophy of carbon/g-C3N4 composites and the advanced studies are exemplified in detail. Finally, a nichetargeting summary and outlook on the major challenges, opportunities for future research in high-powered carbon/g-C3N4 composites was proposed.

By using a low CO2 concentration as a C1 source, the design of a plasmonic catalyst that can effectively photocatalytic CO2 reduction is of great significance for sustainable and ecological development. Herein, the space confinement effect and liquid environment of the molten salt result in uniform hollow structure, while the strong aggressive force furnished via using molten salt enhances the formation of line defects. This special structure can not only provide a large number of active sites but also greatly accelerate the transport of photoinduced charge carriers. The hollow copper ball with line defects (CCu) shows excellent photocatalytic activity with pure water (1028.57 μmol g−1), and it also shows good catalytic activity even under ultra-low CO2 content, which far exceeds the catalytic activity of most semiconductor-based catalysts. This work is designed to simultaneously construct line defect and hollow structure in plasmatic metal nanoparticles for efficient photocatalytic CO2 reduction.

Although kesterite Cu2ZnSnS4 (CZTS) has emerged as a potential absorber material for development of low cost thin film solar cells, the performance of the CZTS devices has been limited by a large deficit in open circuit voltage caused by recombinations of charge carriers primarily at the back contact interface. Recently, field passivation through engineering of the back contact interface has been shown to control the interface recombination and thereby minimise the open circuit voltage deficit. In this work, we have numerically established the limiting role of defect densities in the bulk of CZTS and at interfaces (CZTS-CdS and CZTS-Mo) on performance metrics of the champion CZTS cell (∼11%). Furthermore, we have shown that field passivation by using back surface field (BSF) layers in the form of very thin p+ type Cu2O and SnS layers, sandwiched between the bottom electrode Mo and CZTS, greatly improved the device efficiency (to about 15%) despite significant high bulk and interface defect densities. Numerical calculations have revealed critical dependence of back contact interface recombination on charge carrier concentration gradient and band offset at the interface, and thickness of the BSF layer. Based on the results, a mechanism for suppressing the recombinations at back contact interface has been illustrated.

Highly photoactive FeVO4 photoanodes with ordered nanoblock morphology and uniform Ti-doping were prepared by drop-casting mixed Ti and V precursors onto FeOOH nanorod films and following an annealing process. The results indicate that Ti4+ is uniformly doped into the FeVO4 lattice by substituting V5+ and provides an increased number of O2– vacancies. The optimized film thickness and doping level are 620 nm and 0.3%, respectively. Compared to the undoped sample, the Ti-doped photoanode showed ~ 219% enhancement in photocurrent at 1.0 V vs Ag/AgCl under back illumination of AM 1.5, reaching a state-of-the-art value of ~ 1.47 mA cm−2, and also achieved stable and efficient overall water splitting activity with evolution rates of 28.3 and 14.1 μmol cm−2h−1 for H2 and O2, respectively. The excellent PEC performance could be attributed to the remarkably enhanced charge carrier concentration and conductivity, and the facilitated charge transfer kinetics across the semiconductor/electrolyte interface, as a result of Ti-doping.

Constructing heterostructures with narrow-band-gap semiconductors is a promising strategy to extend light absorption range of graphitic carbon nitride (g-C3N4) and simultaneously promote charge separation for its photocatalytic activity improvement. However, its highly localized electronic states of g-C3N4 hinder photo-carrier migration through bulk towards heterostructure interfaces, resulting in low charge carrier separation efficiency of solid bulk g-C3N4-based heterostructures. Herein, porous g-C3N4 (PCN) material with greatly shortened migration distance of photo-carriers from bulk to surface was used as an effective substrate to host CdSe quantum dots to construct type II heterostructure of CdSe/PCN for photocatalytic hydrogen production. The homogeneous modification of the CdSe quantum dots throughout the whole bulk of PCN together with proper band alignments between CdSe and PCN enables the effective separation of photo-generated charge carriers in the heterostructure. Consequently, the CdSe/PCN heterostructure photocatalyst gives the greatly enhanced photocatalytic hydrogen production activity of 192.3 μmol h−1, which is 4.4 and 8.1 times that of CdSe and PCN, respectively. This work provides a feasible strategy to construct carbon nitride-based heterostructure photocatalysts for boosting visible light driven water splitting performance.

In this study, Al-doped Cu2-xAlxZnSnS4 (x = 0%, 1%, 2%, 3%, and 4%) nanoparticles have forged using a simple hydrothermal method. The effect of Al doping on the structural, morphological, and thermoelectric properties have investigated and it has found that Al occupies the Cu site and acts as an acceptor dopant. As compared to un-doped Cu2ZnSnS4, the electrical conductivity and Seebeck coefficient improved with the increase in Al doping concentration leads to a noticeable improvement in power factor. Meanwhile, increased grain size with the doping of higher radius atoms causes the improvement in the mobility of the charge carriers and hence electrical conductivity (27.31–36.1 S/cm). The Seebeck coefficient value has also improved by the energy filtering effect at the grain boundaries. As a result, the Al-doped sample (4%) has achieved maximum power factor value (1.82 × 10−7 Wm−1K−2), which is roughly 35% higher than pure CZTS.

This paper reports the prospect of strained Si/Si1-xGex nano-scale p++-i-n++ photo-detector in the infrared (IR) wavelength region (1000nm-2200nm). The proposed device is capable of offering high photo-responsivity and quantum efficiency at 1600 nm wavelength in comparison to the unstrained conventional Si based pin photo-detector device. The authors have developed a Quantum Modified Drift Diffusion Model to analyze the nano-scale properties of strained Si photo-detector device. The analysis reveals that the strained Si based pin photo-detector offers high photo responsivity 0.67 A/W at 1600nm wavelength and quantum efficiency 0.60 at the same wavelength compared to the conventional unstrained Si based photo-detector. The enhancements of the photo electric characteristics of the Si photo device are obtained by incorporating selective amount of Ge into the Si active region. The electrical properties in the strained Si semiconductor at room temperature (300K), have made this material more attractive for being used as a photodetector. Due to the incorporation of this Ge layer, in-plane biaxial strain is produced in the active region. This phenomenon enhances the out-of-plane mobility of charge carriers. In this current research, in-plane strain is used to boost up the outplane mobility depending on the geometrical structure of the active region. The validity of the proposed model is established by comparing the simulated data with the corresponding experimental results. The authors also report the reliability study of the proposed device in details. Further, the authors have developed a 4x4 array type photo-detector based on the strained Si structure and the results are compared with the corresponding single array type photo-detector. In case of the 4x4 array type photo detector, the photo electric characteristics i.e. photo responsivity and quantum efficiency increase to 0.74 A/W and 0.69 respectively at 1600nm wavelength. In IR wavelength region, the designed photo-sensor depicts a significant improvement of performance compared to the available photo-detector in published research work. The proposed photo-detector can play an important role in Biomedical, Defence and Agro industries. According to the authors’ knowledge, this is the first report on strain engineered nano scale asymmetrical Si/Si1-xGex based photo-detector array.

Here we report tuning of structural parameters of La2Sn2O7 by Nd substitution at La-site in a quest to effectively control the dielectric response as a small variation in lattice parameters can result in large dielectric fluctuations. For this purpose, a series of Nd-substituted La2Sn2O7 was synthesized using sol gel auto-combustion route. The formation of stable cubic pyrochlore phase with consistent variation in the lattice parameters was observed in structural analysis. The morphological investigations revealed a spherical shape of La2Sn2O7 particles which transformed to diamond like shape with a systematic variation in grain size by increasing the Nd contents. The variation in grain size dominantly affected the dielectric dispersion in the vast frequency range. Less energy loss and improved dielectric properties make La1.2Nd0.8Sn2O7 a potential candidate for utilization in energy storage devices. The complex modulus analysis provided an insightful view which helped to distinguish the mobility range of charge carriers in different frequency ranges.

In this work, Bi2WO6/TiO2 nanorod heterojunction was prepared by sonochemical assisted impregnation method. After loading 2 wt% Bi2WO6 on TiO2 nanorods, the photocatalytic hydrogen production rate of 2026 µmol/h/g was achieved. Compared to commercial P25 and TiO2 nanorods, ∼13 and ∼3 folds enhanced activity was observed. The excellent photocatalytic performance of Bi2WO6/TiO2 nanorod photocatalyst was mainly attributed to i) reduction of bandgap due to heterojunction formation, ii) quick transport of photogenerated charge carriers, and iii) efficient charge carrier separation supported by UV-DRS, photocurrent measurement, Impedance study, and photoluminescence spectra analysis. The Z-scheme band alignment for Bi2WO6/TiO2 nanorod heterojunction was proposed based on the Mott-Schottky measurement. This result demonstrated the effective utilization of Z-scheme heterojunction of Bi2WO6/TiO2 for photocatalytic reduction application.

The heterostructure between two semiconductor materials that had suitable band edge positions can contribute to the separation of photoelectrons and holes. In this paper, the heterostructure MoS2-C-g-C3N4 photocatalysts were in-situ synthesized at one-pot high temperature processing. The obtained 0.4 MoS2-C-g-C3N4 composites displayed the highest photocatalytic hydrogen evolution activity with a corresponding H2 evolution rate of 238 μmol g−1h−1, which was about 4.5 times higher than that of 3% C-g-C3N4, and the photocatalyts exhibited excellent stability which was used for photocatalytic hydrogen evolution reaction for 12 h. The 0.4 MoS2-C-g-C3N4 sample displayed well degradation activities for MO, MB, RhB, MR and Ar18, and the scavenging studies indicated the major involvement of ·O2– radicals in the degradation process. The enhanced photocatalytic activity of MoS2-C-g-C3N4 composite was predominantly attributed to the synergistic effects of type II heterostructure between g-C3N4 and MoS2, which effectively accelerated the transfer and separation of photogenerated charge carriers. Besides, the introduction of noble metal-free MoS2 co-catalyst further improved visible light absorption and provided more active sites for H2 evolution reaction. Such work is promising for designing a novel heterostructure photocatalysts for solar-to-fuel conversion and environmental modification.