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This review focuses on the discussion of the latest progress and remaining challenges in selected metal-free photocatalysts for hydrogen production. The scope of this review is limited to the metal-free elemental photocatalysts (i.e. B, C, P, S, Si, Se etc.), binary photocatalysts (i.e. BC3, B4C, CxNy, h-BN etc.) and their heterojunction, ternary photocatalysts (i.e. BCN) and their heterojunction, and different types of organic photocatalysts (i.e. linear, covalent organic frameworks, microporous polymer, covalent triazine frameworks etc.) and their heterostructures. Following a succinct depiction of the latest progress in hydrogen evolution on these photocatalysts, discussion has been extended to the potential strategies that are deemed necessary to attain high quantum efficiency and high solar-to-hydrogen (STH) conversion efficiency. Issues with reproducibility and the disputes in reporting the hydrogen evolution rate have been also discussed with recommendations to overcome them. A few key factors are highlighted that may facilitate the scalability of the photocatalyst from microscale to macroscale production in meeting the targeted 10% STH. This review is concluded with additional perspectives regarding future research in fundamental materials aspects of high efficiency photocatalysts followed by six open questions that may need to be resolved by forming a global hydrogen taskforce in order to translate bench-top research into large-scale production of hydrogen.

Earth abundant iron pyrite (FeS2) has attracted considerable attention as a potential non-toxic absorber material in lieu of widely used but toxic and relatively rare Indium containing CIGS and CdTe for thin-film solar cells. Research in this regard has been progressed in understanding its fundamental electronic, optical and chemical properties, while its surface polarity is rarely been studied. In this contribution, we have investigated the adhesion of water to determine the wettability (i.e. hydrophilic or hydrophobic) of naturally grown FeS2, and thereof, the polarity of the surface. FeS2 has a cubic crystal structure that grows and cleaves along its cubic faces. Based on the measurements using Sessile drop method, we have found that the surfaces of the pyrite phase of FeS2 crystals are intrinsically super-hydrophilic and highly polar. Our finding is corroborated with X-ray diffraction, Fourier Transform Infrared, Raman Spectroscopy, particle size determination, and contact angle measurements of the pyrite phase. The surface polarity would be a critical factor for choosing surface passivation protocols and type of contact materials as well as for interpreting surface field effects in the system for solar cell application with material heterojunctions.

Photocatalytic solar fuel production, for example, production of hydrogen via water-splitting, is an effective means of chemical storage of solar energy and provides a potential option for achieving a zero-emissions energy system. Conveniently, hydrogen can be converted back to electricity either via fuel cells or through combustion in gas turbines, or it can be mixed in low concentrations with natural gas or biogas for combustion in existing power plants. The cornerstone of a practical solar fuel production process is a stable, efficient, and scalable photocatalyst (a semiconductor material that accommodates photon absorption, charge carrier generation and transport, and catalytic reactions). Therefore, the quest for suitable photocatalyst materials is an ongoing process. Recently, carbon nitride (CN) has attracted widespread interest as a metal-free, earth-abundant, and highly stable photocatalyst. However, the catalytic efficiency of CN is not satisfactory because of its poor charge transport attributes. There is a direct relation between the photocatalytic efficiency and charge transport because the basic principle of light-promoted overall photodecomposition of water into H

This work clarified the conventional/phase shift dual Mach–Zehnder modulation measured technique for upgrading radio over fiber (ROF) systems. Four levels of pulse amplitude modulation and non-return to zero code scheme are employed in different previous studies for upgrading ROF systems. The possible transmission distance is extended to 150 km and a bit rate of 40 Gb/s for achieved acceptable max. Q factor of 13.7498 and minimum bit error rates of 1.82×10–43. The total optical received power is measured at fiber cable length for maximum distance. Also, in the same way, the signal power levels are measured after fiber optic cable and avalanche photo detector optical receiver. The proposed model has presented the enhancement percentage ratio of 13.654% over the previous models in signal quality enhancement.

In pursuit of inexpensive and earth abundant photocatalysts for solar hydrogen production from water, conjugated polymers have shown potential to be a viable alternative to widely used inorganic counterparts. The photocatalytic performance of polymeric photocatalysts, however, is very poor in comparison to that of inorganic photocatalysts. Most of the organic photocatalysts are active in hydrogen production only when a sacrificial electron donor (SED) is added into the solution, and their high performances often rely on presence of noble metal co‐catalyst (e.g. Pt). For pursuing a carbon neutral and cost‐effective green hydrogen production, unassisted hydrogen production solely from water is one of the critical requirements to translate a mere bench‐top research interest into the real world applications. Although this is a generic problem for both inorganic and organic types of photocatalysts, organic photocatalysts are mostly investigated in the half‐reaction, and have so far shown limited success in hydrogen production from overall water‐splitting. To make progress, this article exclusively discusses critical factors that are limiting the overall water‐splitting in organic photocatalysts. Additionally, we also have extended the discussion to issues related to stability, accurate reporting of the hydrogen production as well as challenges to be resolved to reach 10 % STH (solar‐to‐hydrogen) conversion efficiency., While half‐reactions using organic photocatalysts for hydrogen production are encouraging, systems with high efficiency without using sacrificing electron donors (SED) and showing full overall water‐splitting are still largely absent. Critical factors that are limiting the overall water‐splitting using organic photocatalysts are summarized, with a supplementary discussion on remaining challenges.

Lead halide perovskites (LHPs) have recently emerged as promising materials for solar energy conversions. Here, the underlying optoelectronic properties, charge transport abilities, energy level positions for alignment of contact materials, and the stability of LHPs are all dependence on the material composition and structure. Therefore, understanding the structure-to-property relationships is crucial from both a fundamental perspective as well as for constructing efficient and stable devices based on LHPs. XRD is a century old powerful tool to extract the structure of crystalline materials. It provides means to quantify atomic level distances, extraction of symmetries, densities, compositional and temperature dependent phase transitions as well as orientation and size of crystallites in polycrystalline films. Raman spectroscopy is a versatile characterization technique that provides information about the chemical composition and phases in crystalline materials, as well as the local vibration found in amorphous structures, molecular materials, solvents, and gases. With this knowledge, one can extract chemical identities via observed vibrations, bonding interactions, orientations, symmetries, local and lattice vibrations in a crystalline materials. In this contribution, we succinctly discuss the latest progress in understanding the physical properties of LHPs using XRD and Raman Spectroscopy.

This work was intended to clarify if the dyeing treatment could modify the functional properties of white substrate as well as the surface finishing would alter the initial color of dyed textiles. Thus, in this work, a kind of surface coating was applied to modify the flame retardant and hydrophilic properties of both the undyed (white) and dyed polyamide 6.6 (PA6.6) textiles using some novel compounds like chitosan (CS), montmorillonite (MMT), sodium alginate (ALG) and phytic acid (PA) in a quadralayer (QL) or a hexalayer (HL) fashion. The obtained results revealed that the dyed fabric samples exhibited better flame retardancy and hydrophilicity compared to the undyed one; indicating the dyeing treatment contributed in improving the functional properties. For example, the 5HL-deposited dyed fabric sample (i.e., PA6.6-D-5HL) showed a maximum reduction in the peak heat release rate (pHRR) by 32% and the 7.5QL-deposited dyed fabric sample (i.e., PA6.6-D-7.5QL) brought a water contact angle (WCA) value of 0°. However, this kind of surface finishing caused a slight loss in depth of color for the dyed fabric samples.

We here introduce, for the first time, a topological carbon nitride (TCN) with built-in crystalline–amorphous phases. Topologically anchored dual complementary phases allow localized photon absorption of different wavelengths, and provide a twinned photocatalyst interface to facilitate geminate charge carrier pair separation. These unique attributes, which are absent in widely used graphitic carbon nitride (GCN) and amorphous carbon nitride (ACN) photocatalysts, are highly desirable for precious metal (i.e. Pt) cocatalyst-free hydrogen production via water-splitting. Our results are substantiated with both experiments and simulations.

DyCrO3 and 10% Fe-doped DyCrO3 nanoparticles have been synthesized using a sol–gel method to investigate their performance in photocatalytic hydrogen production from water. The synthesized nanoparticles have been characterized by performing X-ray diffraction, energy dispersive X-ray spectroscopy and UV-visible spectrophotometric measurements. In addition, field emission scanning electron microscopy has been performed to observe their size and shape. The Fe-doped DyCrO3 nanoparticles show a significantly smaller band gap of 2.45 eV compared to the band gap of 2.82 eV shown by the DyCrO3 nanoparticles. The Fe-doped DyCrO3 nanoparticles show better photocatalytic activity in the degradation of rhodamine B (RhB) compared to the photocatalytic activity shown by both the DyCrO3 and Degussa P25 titania nanoparticles. The recycling and reuse of Fe-doped DyCrO3 four times for the photo-degradation of RhB shows that Fe-doped DyCrO3 is a stable and reusable photocatalyst. To evaluate the extent of the photocatalytic hydrogen production ability of the synthesized nanoparticles, a theoretical model has been developed to determine their “absorptance”, a measure of the ability to absorb photons. Finally, 10% Fe-doped DyCrO3 proves itself to be an efficient photocatalyst as it demonstrated three times greater hydrogen production than Degussa P25.

Perovskites have emerged as one of the hottest solar cell materials in the recent years, evident by more than 6,000 publications in 2018. Although intense research efforts on perovskite materials have made a significant progress in understanding its fundamental physicochemical properties, a long-term stability of perovskite solar cells (PSC) under operating conditions remains elusive. This article previews the recent findings on most stable PSC to date. Notably, an integrated effort of collaborative research has presented a simple but broadly applicable method to enhance the long-term operational stability of perovskite solar cells (over 1800 h at 70-75°C) under continuous simulated full-spectrum sunlight, which is up to ten times more stable than previous most stable devices.

To overcome the scarcity of natural resources as construction material and to reduce the hazards from industries, industrial wastes can play a very significant role. In this paper, the influence of glass powder and steel slag is reviewed. It is concluded that glass powder and steel slag can upset some portion of concrete thereby providing significant improvement in mechanical properties of concrete consequently reducing the environmental hazards from industries.

A generalized 2-D analytical model of gate threshold voltage for multiple material gate Tunneling FET (TFET) structures is derived. The model can also be used for calculating threshold voltage of a single metal gate TFET. Surface potential model of a triple material double gate TFET has been developed by applying Gauss's law in the device. From the potential model, physics-based model of gate threshold voltage has been derived by exploring the transition between linear to quasi-exponential dependence of drain current on applied gate bias. The model includes the effect of gate and drain bias, gate material workfunction, oxide thickness, silicon film thickness, gate dielectric, and other device parameters. The accuracy of the proposed model is verified by comparing the results predicted by the proposed model to the results of the numerical model developed in Silvaco, Atlas.

This contribution reports the synthesis, characterization and application of a new ternary homo-heterojunction photocatalyst for improved hydrogen production via water-splitting. The heterostructure is constructed by soft-grafting of graphitic carbon nitride (GCN) and graphene oxide (GO) into an amorphous carbon nitride (ACN) substrate. In this ternary hybrid, a cascaded redox-junction is formed that significantly facilitates the separation of photogenerated electron–hole pairs (EHPs), retards EHP recombination and shuttles electrons to the photocatalyst/liquid interface for proton reduction reactions. When deposited with 3 wt% Pt as a cocatalyst, this new photocatalyst exhibits hydrogen production of 251 μmol h−1 from 10 vol% aqueous triethanolamine solution under visible light (420 nm) irradiation with an apparent quantum efficiency of 6.3%. This ternary photocatalyst therefore outperforms stand-alone/binary photocatalysts and promises to be a viable alternative to metal-based photocatalysts.

Considering the natural abundance, the optoelectronic properties, and the electricity production cost, iron pyrite (FeS2) has a strong appeal as a solar cell material. The maximum conversion efficiency of FeS2 solar cells demonstrated to date, however, is below 3%, which is significantly below the theoretical efficiency limit of 25%. This poor conversion efficiency is mainly the result of the poor photovoltage, which has never exceeded 0.2 V with a device having appreciable photocurrent. Several studies have explored the origin of the low photovoltage in FeS2 solar cells, and have improved understanding of the photovoltage loss mechanisms. Fermi level pinning, surface inversion, ionization of bulk donor states, and photocarrier loss have been suggested as the underlying reasons for the photovoltage loss in FeS2. Given the past and more recent scientific data, together with contradictory results to some extent, it is timely to discuss these mechanisms to give an updated view of the present status and remaining challenges. Herein, the current understanding of the origin of low photovoltage in FeS2 solar cells is critically reviewed, preceded by a succinct discussion on the electronic structure and optoelectronic properties. Finally, suggestions of a few research directions are also presented.

We describe here the metal-templated transformation of carbon nitride (C3N4) into nitrogen-containing carbons as anodes for Li-ion batteries (LIBs). Changing the template from the carbon- and nitrogen-immiscible Cu powder to the carbon- and nitrogen-miscible Fe powder yields different carbons; while Fe templating produces graphitized carbons of low (

Polymeric melon shows real promise to be a next generation photocatalyst material for solar hydrogen production. Because it is earth abundant, and highly stable in photoredox reactions. However, a long-standing problem with polymeric melon is that it is inactive for photocatalytic hydrogen evolution without a metal cocatalyst, such as Pt. Sluggish charge transfer kinetics and a high activation energy for proton reduction makes pristine melon overly dependent on a high loading of precious Pt-cocatalyst for hydrogen evolution. While Pt-assisted hydrogen evolution is not considered economic for scale-up, a modulation of intrinsic photophysical and physicochemical properties of melon is therefore crucial to overcome the Pt dependency. However, to our knowledge, no systematic study has been reported to date to make melon independent of Pt for solar hydrogen evolution. Here we show that the limiting factors of Pt-dependent hydrogen production can be overcome by amorphization. The amorphization lowers the band gap, shifts the proton reduction potential close to the origin, and enhances the light harvesting and charge transport. Therefore, it results in a Pt-free hydrogen evolution under visible light irradiation. We here also present a mechanistic understanding of the origin of this cocatalyst-free hydrogen evolution.

A dual interaction-based (i.e., ionic/covalent) deposition of carbohydrate polymers, namely chitosan (CS) and oxidized sodium alginate (OSA) along with a plant-derived phosphorus-rich compound like phytic acid (PA) and a nitrogen rich compound like melamine (ME) was considered onto the phosphorylated chitosan (PCS) modified polyamide 6.6 (PA6.6) fabric surfaces in order to impart durable flame retardancy along with super-hydrophilicity of the same. Firstly, the pure PA6.6 textile surfaces were modified by PCS via UV-induced grafting and subsequently, the above-mentioned polyelectrolytes were assembled onto the fabric surfaces in a quadralayer fashion [i.e., (CS/ME-OSA-CS/ME-PA) n; “n” represents the number of quadralayers (QLs)]. Here, the amino groups of CS/ME and the aldehyde groups of the OSA were stabilized via covalent interaction and the deposition of positively charged CS/ME and negatively charged phytic acid (PA) formed ionic interaction. In the vertical burning (UL-94) test, both the only PCS grafted and the simultaneously PCS-grafted along with LbL assembled fabrics could completely stop the melt dripping tendency and attained a V-1 rating. In the meantime, the limiting oxygen index (LOI) value received a moderate increase from 18.5 % of pure PA6.6 to 23.5 % for the PCS grafted and 8-QLs deposited fabric sample (i.e., PA6.6-g-PCS-8QL). Moreover, the PA6.6-g-PCS-8QL fabric sample exhibited a dramatic decrease in the peak heat release rate (pHRR) and total heat release (THR) by about 45 % and 24.7 % respectively alongside enhanced thermal stability. Apart from the appreciable flame retardancy, this fabric sample (i.e., PA6.6-g-PCS-8QL) could boost up the hydrophilicity to attain a water contact angle of 0°. Finally, this dual interaction-based deposition of bio-inspired polyelectrolytes posed a positive impact in enhancing the coating stability in laundering and imparting durable flame retardancy to sustain even up to 20 laundering cycles.

A new analytical model for the gate threshold voltage ($$V_\mathrm{TG}$$VTG) of a dual-material double-gate (DMDG) tunnel field-effect transistor (TFET) is reported. The model is derived by solving the quasi-two-dimensional Poisson's equation in the lightly doped Si film and employing the physical definition of $$V_\mathrm{TG}$$VTG. A numerical simulation study of the transfer characteristics and $$V_\mathrm{TG}$$VTG of a DMDG TFET has been carried out to verify the proposed analytical model. In the numerical calculations, extraction of $$V_\mathrm{TG}$$VTG is performed based on the transconductance change method as already used for conventional metal---oxide---semiconductor FETs (MOSFETs). The effects of gate length scaling, Si film thickness scaling, and modification of the gate dielectric on $$V_\mathrm{TG}$$VTG are reported. The dependence of $$V_\mathrm{TG}$$VTG on the applied drain bias is investigated using the proposed model. The proposed model can predict the effect of variation of all these parameters with reasonable accuracy.

Hydrogen from direct splitting of water molecules using photons is reckoned to be a sustainable and renewable energy solution for the post fossil-fuel era. Efficient photocatalysts, including metal-free photocatalysts, are key determinants of cost-effective hydrogen generation at a large-scale. The search for new materials that are metal-free is therefore ongoing. Recently, 2D phosphorene, a phosphorus analogue of graphene, has been added as a new semiconductor to the family of monolayer-flatland materials. In this review, we focus on analysing the fundamental electronic, optical and chemical properties of 2D phosphorene and assess its suitability as a metal-free water splitting photocatalyst. We also critically analyse its stability against claims from environmental antagonists and attempt to predict its future as a photocatalyst. This review provides timely information for researchers, scientists and professionals devoted to materials research for photocatalysis.

The layer by layer (LBL) deposition of chitosan/melamine/urea (CS/ME/UREA) and phytic acid (PA) onto the acrylic acid (AA) grafted Polyamide 6.6 (PA6.6) fabrics including a pad-dry-cure treatment with chitosan/graphene oxide (CS/GO) nanocomposites were considered to improve the hydrophilicity and durable flame retardancy. Obtained results indicated that these hybrid coatings could significantly improve the flame retardancy as the limiting oxygen index (LOI) value reached up to 25 % from 18.5 % and could completely stop the melt dripping where the fabric sample with two bilayers deposition and simultaneously treated with CS/GO nanocomposite (PA6.6-g-AA-2BL-CS/GO) achieved a V-1 rating. A 2BLs deposited hybrid coating (i.e., PA6.6-g-AA-2BL-CS/GO) could decrease the peak heat release rate (pHRR) by 47.1 %; whereas a maximum reduction of pHRR by about 56 % was achieved for 5BLs deposition. Moreover, a considerable improvement in thermal stability and char yield% were also realized in the thermogravimetric analysis (TGA) test. Furthermore, the as-prepared hybrid coatings imparted better hydrophilicity as a 2BLs deposition along with pad-dry-cure treatment by CS/GO could boost up the hydrophilicity of the treated fabrics further compared to the only 2BLs deposited fabric sample. In addition, the application of CS/GO nanocomposite could improve the stability of this coating and able to stop the dripping tendency even after 10 laundering cycles as well.

In this work, prospects of nanocavity embedded Dual Metal Double Gate Tunnel FET device as a label free biosensor have been analyzed for neutral biomolecule detection. A numerical model of the device has been developed in Atlas, Silvaco and device electrical characteristics for the presence of different biomolecules have been observed. Based on the device performance, sensing metrics have been indicated. Sensitivity of the sensing metrics like tunneling current, threshold voltage, Sub-threshold Slope have been analyzed for the presence of varying biomolecules. Additionally, the filling factor of the biomolecules in the cavities has been analyzed. It has also been found that dual metal structure provides better sensitivity than the single metal counterpart.

The electroless and electrolytic deposition of silver from a solution containing silver nitrate in either an ethylene glycol (EG)-choline chloride based or a urea-choline chloride based ionic liquids has been carried out onto steel and copper cathodes by simple immersion, constant current and constant potential methods at room temperature. It has been found that electroless silver deposits of up to several micronshave been obtained by dip coating from both urea and EG based ionic liquids without the use of catalysts. The influences of various experimental conditions on electrodeposition and morphology of the deposited layers have been investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It has been observed that crack free bright metallic coloured silver coatings can be obtained from both EG and urea based ionic liquids at the applied deposition potentials up to -0.40 V and applied deposition current densities up to -5.0 A m-2 at room temperature. The cathodic current efficiency for the deposition of Ag is about 99%.

This paper discussed advances in several suitable passivation schemes and emitter optimization techniques available up to date. c-Si endowed with numerous crystal defects and impurities which are responsible for lower efficiency of solar cells made out of it. The surface passivations and emitter formations are the two inevitable processes to upgrade the solar cells efficiency by circumventing several induced effects due to associated crystal defects and impurities of c-Si. This work will act as a common place for the solar cell researchers, engineers and for the students to get the very recent results of surface passivation and emitter optimization techniques practiced both in the industries and R&D laboratories over the world. Key issues here to be considered while agglomerating the relevant information for each process step are the cost-effectiveness, added complexity, additional benefits, reliability, and efficiency potential.

Pure BiFeO 3 nanoparticles were synthesized by a simple sol-gel method namely modified Pechini method. The nanoparticles were calcinated at four different temperatures (450°C, 550°C, 650°C, 750°C). Requirement for extra washing step for impurity phase reduction has been eliminated by elongation of the drying duration at oven from 12 hours to 28 hours along with intermediate grinding. FESEM and X-ray Diffraction (XRD) were performed which confirm that the samples calcinated at 450°C and 550°C show smaller particle size and greater correspondence. Hence XPS was performed on these two samples which showed lower oxygen vacancies for 550°C. Finally the SQUID analysis has been carried out for the 550°C sample. A higher value of remanent magnetization and coercive field at room temperature has been observed. Besides, an asymmetric shift in the field axis with unsaturated M-H curve may be attributed to the existence of exchange bias effect in the synthesized nanoparticles.

In this work, effect of interface charge on the performance of a Dual Material Double Gate (DMDG) Tunnel Field Effect Transistor (TFET) device has been studied. Due to the presence of high electric field in the device, interface charges are generated at oxide-semiconductor interface by hot carrier effect. A 2-D model of the device with interface charge has been developed in TCAD simulator and impact of both positive and negative interface charges has been observed in potential distribution, band profile, carrier concentration, tunneling current and threshold voltage. Since high electric field mainly exists in the source-body junction of the device, interface charges are mainly localized at that region. Effect of localized charge spreading over varying length has also been analyzed on surface potential and threshold voltage of the device. The study will be useful in fabrication and application of DMDG TFET devices.

The impact of inversion charge layer on triple material double gate (TMDG) Tunnel FET (TFET) has been inspected in this work by using 2D TCAD simulations. Simulation results show that band-to-band tunneling current saturates due to inversion layer formation. Inversion charges cause the pinning of surface potential and make drain current less responsive to gate voltage. The contribution of source and drain in forming the inversion layer is measured quantitatively. The influence of different device parameters on inversion layer formation has also been inspected.

A comparative study has been made to analyze the impact of interstitial iron in minority carrier lifetime of multicrystalline silicon (mc-Si). It is shown that iron plays a negative role and is considered very detrimental for minority carrier recombination lifetime. The analytical results of this study are aligned with the spatially resolved imaging analysis of iron rich mc-Si.

A charge sheet model is proposed to analyze the transistor characteristics of fully depleted SOI four gate field effect transistors (G 4 -FETs). The model is derived assuming a parabolic potential variation between the junction-gates and by solving 2-D Poisson’s equation. The proposed model facilitates the calculation of surface potential and charge densities as a function of all gate biases. Modifying this charge sheet model for non-equilibrium condition, current–voltage and capacitance–voltage characteristics are also analyzed. Different back surface charge conditions are considered for each analysis. The models are compared with 3-D Silvaco/Atlas simulation results which show good agreement.

Triple material double gate (TMDG) tunnel field-effect transistor (TFET) can be considered as a potential nominee for next generation low power high speed device fabrication. In this study, the effect of Si film thickness on performance of TMDG TFET is analyzed using two dimensional TCAD simulations. The tunneling current is substantially dependent on device thickness and the device physics regulating it is outlined. Potential and electric field distributions along film thickness reveal that double gate pairing in TMDG TFET structure can lower the tunneling barrier width at the middle of the device until an optimized silicon film thickness is achieved and provide maximum drain current.

This paper introduces a detailed study of minority carrier lifetime profile into transient anode voltage and current modeling of Non-Punch Through (NPT) Insulated Gate Bipolar Transistor (IGBT). The minority carrier concentration has been modeled through parabolic approximation. With the new approach, an analytical model has been developed for turn-off voltage and current of IGBT in all minority carrier lifetime conditions. Consistency with the experimental results has been found compared to the previously used linear model. Finally, the implications of carrier lifetime dependence on the switching analysis are discussed.

Cotton fabric was dyed by exhaust method with C.I. Reactive Blue 19 with various dye concentrations, followed by the treatments of soaping, dye fixing, and wet rubbing improving. The dye exhaustion, wash fastness, rubbing fastness, and colour difference of dyed cotton fabric were examined. The consequences demonstrate that the entire utilized textile auxiliaries did not cause a yellowness problem. After application of the dye fixative and wet rubbing improver, to the deep blue shade cotton (15% dye o.m.f), the wash fastnesses were all at grade 5, and at grade 5 and 4 of dry and wet of rubbing fastness respectively. The wet rubbing improver contributed to deep blue shade and promoted half grade in wet rubbing for all dye o.m.f.

Cotton fabric was dyed with C.I. Reactive Black 5 with different dye mass, followed the treatments of soaping, dye fixing, and wet rubbing improving. The wash fastness, rubbing fastness, and colour uniformity of dyed cotton were inspected. The results show that the entire utilized textile auxiliaries did not cause a yellowness problem. After application of the dye fixative and wet rubbing improver, to the deep black shade cotton (15% o.m.f), the wash fastnesses were all at grade 5, and reached at grade 5 and 3-4 of dry and wet of rubbing fastness respectively. The wet rubbing improver improved half grade of wet rubbing for dye o.m.f less than 8%, but did not have any contribution for deep shade.

A mathematical model is developed to determine the subthreshold swing of thin-film fully depleted silicon-on-insulator four-gate transistors (G4-FETs). The model is developed using a 2-D model of potential distribution that was derived from 2-D Poisson's equation. Study reveals that the subthreshold swing is a strong function of back-surface charge condition and depends on structural parameters of the device. Excellent agreement with 3-D device simulations is observed.

Crystalline silicon (c-Si) solar cells have the lion share in world PV market. Solar cells made from crystalline silicon have lower conversion efficiency, hence optimization of each process steps are very important. Achieving low-cost photovoltaic energy in the coming years will depend on the development of third-generation solar cells. Given the trend towards these Si materials, the most promising selective emitter methods are identified to date. Current industrial monocrystalline Cz Si solar cells based on screen-printing technology for contact formation and homogeneous emitter have an efficiency potential of around 18.4%. Limitations at the rear side by the fully covering Al-BSF can be changed by selective emitter designs allowing a decoupling and separate optimization of the metallised and non-metallised areas. Several selective emitter concepts that are already in industrial mass production or close to it are presented, and their specialties and status concerning cell performance are demonstrated. Key issues that are considered here are the cost-effectiveness, added complexity, additional benefits, reliability and efficiency potential of each selective emitter tech- niques.

In many power converter applications, minority carrier lifetime assessment in the carrier storage region of IGBT is considered desirable. This paper presents a minority carrier lifetime estimation technique through investigation into transient base charge modeling of Non-punch Through (NPT) Insulated Gate Bipolar Transistor (IGBT). Parabolic approximation has been used for derivation of minority carrier concentration within the base. With the help of derived expression, an analytical model has been developed for transient base charge decay of IGBT in all minority carrier lifetime conditions. Better agreements with the experimental results have been found compared to the previously used linear model. Finally, the implications of carrier lifetime dependence on the charge decay rate are discussed, including implementation of such a carrier lifetime measurement technique.

In many power converter applications, study of doping concentration in the carrier storage region of IGBT is considered desirable. This paper introduces an estimation technique for base doping concentration through investigation into transient anode voltage modeling of Non-punch through (NPT) Insulated Gate Bipolar Transistor (IGBT). Parabolic profile has been used for derivation of minority carrier concentration within the base. With the derived expression, an analytical model has been developed for turn-off anode voltage of IGBT in all doping profile conditions. Better agreements with the experimental results have been found compared to the previously used linear model. Finally, the implications of base doping dependence on the anode voltage are discussed, including implementation of such a doping concentration estimation technique.

Dual Metal double gate tunnel field-effect transistor (DMDG TFET) is a potential candidate for the next generation device fabrication. In this work a 2-D analytical model of the surface potential, electric field of DMDG TFET is developed by solving quasi-two-dimensional Poisson equation. These expressions can be numerically integrated to find the drain current. This model incorporates the effects of drain voltage, gate work function, gate length, gate dielectric thickness and silicon film thickness. The effectiveness of the proposed model is confirmed by a comparison with 2-D numerical simulations.

The performance and characteristics of Double Gate MOSFET with high dielectric constant (high-κ) gate stack have been analyzed and compared with those of conventional pure SiO2 gate MOSFET. Quantum Ballistic Transport Model has been used to demonstrate the performance of the device in terms of threshold voltage, drain current in both low and high drain voltage regions and subthreshold swing. The effect of temperature on the threshold voltage and subthreshold characteristics has also been observed. This work reveals that improved performance of this structure can be achieved by scaling the gate length and illustrates its superiority over SiO2 gate MOSFETs in achieving long-term ITRS goals.

The low quantum yield of photocatalytic hydrogen production in carbon nitride (CN) has been improved upon via the modulation of both the extrinsic and intrinsic properties of the material. Although the modification of extrinsic properties has been widely investigated in the past, recently there has been growing interest in the alteration of intrinsic properties. Refining the intrinsic properties of CN provides flexibility in controlling the charge transport and selectivity in photoredox reactions, and therefore makes available a pathway toward superior photocatalytic performance. An analysis of recent progress in tuning the intrinsic photophysical properties of CN facilitates an assessment of the goals, achievements, and gaps. This article is intended to serve this purpose. Therefore, selected techniques and mechanisms of the tuning of intrinsic properties of CN are critically discussed here. This article concludes with a recommendation of the issues that need to be considered for the further enhancement in the quantum efficiency of CN photocatalysts.

Photoinduced charge separation against their faster recombination is a rate determinant for photocatalytic proton reduction to hydrogen. Dissociation of electron-hole pairs into free electrons and holes in carbon nitrides greatly suffered from the inherent high recombination rate. This study has shown that coupling two energetically optimized, but with different phases carbon nitrides in the form of hybrid could significantly inhibit the charge carrier recombination and facilitate the overall charge transfer processes. It is also found that the potential gradient in this homojunction delocalizes electrons and holes, and increases the spatial charge separation. Therefore, this leads to a record high apparent quantum efficiency of 5% for photocatalytic H2 production from water under visible light irradiation in the absence of a precious metal (e.g., Pt) cocatalyst.

This model describes the production and destruction mechanism of nitrogen plasma at atmospheric pressure. We have studied the mechanisms of chemical dissociation, ionization, ion conversion and recombination in nitrogen plasmas, with kinetic temperature (Tg) of the free electrons being higher than the kinetic temperature (Tg) of heavy species. Therefore, the investigation of nitrogen plasma species in a wide range of pressure from 1 Torr to 760 Torr is interesting phenomena for obtaining the equilibrium state when the nitrogen species breakdown. In order to calculate the species densities to reach thermodynamic equilibrium under various conditions, a set of chemical kinetic reactions of nitrogen under consideration have been simulated. It solves the particle balance equations for a set of interacting species. In this study 16 reactions and 4 species of Nitrogen N, N2, N+, N2+ and electron have been considered. The densities of the charged and neutral species are modeled by continuity equations which includes the relevant plasma-chemical kinetics. Nitrogen species density is guided by continuity equation where chemical processes and Arrhenius form are used to follow the change of species density over the time. To calculate the species densities over pressure, temperature and time the continuity equations of the 16 reactions for the 5 species under consideration giving their initial pressure, densities and temperatures, with the latter held constant have been solved. The variations of species densities have been investigated as a function of pressure ranging from 1 to 760 Torr. This model shows that as the pressure is increased the species densities of nitrogen plasma also increase from pressure 1 to 200 Torr and after pressure above 200 Torr the species densities become almost saturated. The change of species densities at various temperatures ranging from 2000 Kelvin to 25000 Kelvin is successfully investigated. The destruction and production rates of the nitrogen species also have been calculated within the time ranging from 0 to 19nS and it shows that the density of nitrogen plasma increases with time. In our study we have considered the gas and electron temperature as 10k Kelvin and 4eV respectively.

Accurate determination of a material’s optical band gap lies in the precise measurement of its absorption coefficients, either from its absorbance via the Beer–Lambert law or diffuse reflectance spectrum via the Kubelka–Munk function. Absorption coefficients of powder-form nanomaterials calculated from absorbance spectrum do not match those calculated from diffuse reflectance spectrum, implying the inaccuracy of the traditional optical band gap measurement method for such samples. We have modified the Beer–Lambert law and the Kubelka–Munk function with proper approximations for powder-form nanomaterials. Applying the modified method for powder-form nanomaterial samples, both absorbance and diffuse reflectance spectra yield exactly the same absorption coefficients and therefore accurately determine the optical band gap.

Perfluoropolyether (PFPE) fluids are used satisfactorily on magnetic recording media, in the aerospace industry, and in satellite instruments. These oils have been used as hydraulic fluids, high-temperature liquid lubricants in turbine engines, and base oils for high-temperature greases. Despite considerable research on PFPE, the rheological characteristics at high pressure and their effects on the life of ball bearings have not been investigated completely. First, high-pressure density measurements of three kinds of commercial PFPE fluids (fluid K, fluid D, and fluid F) were made from temperatures 293 K to 333 K and pressures up to 1.2 GPa for estimation of the free volume. The density-pressure-temperature relation and viscosity-pressure-temperature relation of PFPE fluids were proposed based on the free volume and the phase diagram. Next, the effect of PFPE fluids on ball bearing fatigue life was determined by systematic tests using thrust ball bearings. The general tendency of PFPE fluids shows that be...

The acoustic emission (AE) technique was applied to rolling contact fatigue tests using a test-rig running under constant load and speed for detecting the incipient damage and damage location. This incipiently-damaged roller was investigated in detail and monitored by further running to determine the damage severity and to understand the surface damage propagation process by applying the AE techniques. The conventional AE parameters and AE signal features were studied, and their relation with the AE source locator hit count rate were correlated. The results demonstrated the successful use of the AE measurement unit, which is principally, consists of the AE data analyzer and the AE source locator as a new system for detecting incipient damage produced by fatigue. Moreover, the system is able to forecast the position of the damage in the roller, capable of providing an indication of the severity of damage i.e. damage size, and thus it could allow the user to monitor the rate of further degradation of the rolling elements.

A silicon on insulator field effect transistor for cryogenic operation has been fabricated using a sol-gel derived TiO2 electron beam resist as a high-k gate dielectric and characterized over a range of temperatures. The TiO2 dielectric layer allows too large a gate leakage current for good device operation at room temperature, but the leakage current is strongly suppressed at cryogenic temperatures and good transistor characteristics were observed. The temperature dependence of the gate leakage current suggests that Frenkel-Poole and trap-assisted tunneling dominates the conduction in the dielectric layer. The drain current shows peaks at certain frequencies under continuous wave microwave irradiation, which may be caused by the resonance of electrons trapped in defects at the TiO2/SiO2 interface. These resonances offer the possibility to manipulate single electrons for nonclassical information processing.

Acoustic emissions (AE) technique was applied to rolling contact fatigue tests of two radially loaded rollers running under constant load and velocity to detect the incipient damage and damage location. Signals detected from contacts were processed using signal conditioning and enhancement techniques by an AE source locator to bring out the difference between the signals from the sound and damaged rollers. It was found that AE hit count pulse observations by the AE source locator can provide an indication of the damage at its initial stage. The conventional AE parameters and the AE signal features were studied and correlated with the AE source locator counts. The results demonstrated the successful use of the combination of the AE monitoring and the AE source locator as a new technique for detecting the incipient damage and forecasting the position of the damage in the roller, and this technique could allow the user to monitor the rate of deterioration of the rolling elements.

The study highlighted the potentiality and effectiveness of Acoustic Emission (AE) signals monitoring along with data clustering analysis as a powerful tool applicable to the rolling elements under examination for incipient damage failure. The AE technique was applied to rollers in contact using rolling contact fatigue test-rig running under constant load and speed for detecting the incipient damage initiation and its damage location. The results demonstrated the successful use of the AE activity monitoring combination with AE source locator and AE data analyzer as a new technique for incipient damage detection. The recorded AE signals from run-to-incipient damage life testing were investigated by unsupervised clustering analysis to examine and to produce numerical validation of the results by separating AE sources data into several classes that reflected the internal structure of the data during contact. A methodology including descriptor selection, methods, procedures for numerical verification and cluster validity criteria were followed.

This work presents a minority carrier lifetime estimation technique through investigation into transient anode voltage modeling of Non-punch Through (NPT) Insulated Gate Bipolar Transistor (IGBT). Parabolic approximation has been used for derivation of minority carrier concentration within the base. With the help of derived expression, an analytical model has been developed for turn-off voltage of IGBT in all minority carrier lifetime conditions. Better agreements with experimental data have been found compared to the linear model generally used. Finally, the implications of carrier lifetime dependence on the anode voltage are discussed, including implementation of such a carrier lifetime measurement technique.

An empirical expression for the base transit time, τb , of a bipolar transistor with exponential base doping profile is derived considering doping and field dependence of mobility. In the analysis, bandgap-narrowing effect, high injection effect and carrier velocity saturation at the base edge of the collector-base junction are also incorporated. The collector current density, Jc , and minority carrier stored charge, Qb , in the base are separately expressed as a function of the injected electron density no in the base in order to find an empirical expression for τb . The modelling of Jc , Qb and τb is essential for the design of a modern bipolar transistor. The base transit time calculated analytically is compared with simulation and numerical results in order to demonstrate the validity of the assumptions made in deriving the expression. The base transit time is found to be different if the field dependent mobility is considered.