Acceptor Concentration Research Articles

Potentiostatic electrodeposition of copper, indium, and cadmium sulfides for CO2 electroreduction: A path toward sustainable hydrogen generation

This study focuses on the potentiostatic electrodeposition of copper indium and cadmium sulfide (CuS, In2S3, and CdS) thin films on copper substrates, aiming to develop efficient electrocatalysts for the electrochemical reduction of CO2 and sustainable hydrogen generation. Utilizing Cu Kα radiation for X-ray diffraction (XRD) analysis, the crystal structures of the electrodeposited films were confirmed, revealing well-defined crystalline phases. The films exhibited average particle sizes of 55.99 nm for CuS, 50.37 nm for In2S3, and 63.51 nm for CdS. Cyclic voltammetry and chronoamperometry were employed to optimize the deposition parameters, ensuring efficient nucleation and growth of the metal sulfide films. The electrochemical performance of the synthesized electrocatalysts was rigorously tested, demonstrating their potential for CO2 reduction under optimized conditions with the highest efficiency for CdS electrodes. Additionally, the electrodeposited CuS and CdS are of the p-type, and In2S3 is of the n-type semiconductor were studied and verified by the Mott–Schottky test. CuS, In2S3, and CdS were found to have donor and acceptor concentrations (ND) of 1.68 × 106, 1.44 × 105, and 8.9 × 105 cm3, respectively. The photoelectrochemical measurements of the electrodeposited metal sulfides were studied at ambient temperature and under illumination, providing higher photocurrent responses for CdS and demonstrating its strong potential as a photoelectrode material for CO2 reduction. This work underscores the significance of facile electrochemical synthesis methods in developing cost-effective and scalable electrocatalysts, paving the way for their integration into photoelectrochemical systems for green energy applications.

Stokes and anti-Stokes emission characteristics of Er3+/Yb3+ co-doped zinc tellurite glasses under 377 and 1550 nm excitations for solar energy conversion application

One of the best rare earth combinations for down- and up-converting the solar photons is Er3+/Yb3+. Therefore, at present, by using the traditional melt quench technique, zinc tellurite glasses doped with Er3+ and Er3+/Yb3+ were characterised. Several methods of down-conversion that result in the emission of 1000 nm from the acceptor (Yb3+) under excitation of donor (Er3+) were studied. On the other hand, the impact of acceptor (Yb3+) concentration and excitation pump power on the excited state absorption and its influence on the up-conversion emission (1000 nm) properties were investigated in detail under 1535 nm excitation. The studies on emission and decay results are discovered to be very significant. Suggesting that these glasses when used as conversion layers, can append the conversion efficiency of Si-based solar cells.

Carrier scattering and temperature characteristics of mobility and resistivity of Fe-doped GaN

Abstract The electron mobility and dark resistivity of Fe-doped semi-insulating GaN (GaN:Fe) are calculated over the temperature range from 10 K to 500 K by considering the impurities compensation mechanism and majority carrier scattering. The temperature characteristic curve of the mobility exhibits unimodality and the curve of resistivity decreases monotonically with rising temperature. The carrier scatterings induced by ionized impurities, acoustic deformation potential, piezoelectric, and polar optical phonons are analyzed. It is found that the mobility is determined by ionized impurity scattering, piezoelectric scattering, and polar optical phonon scattering in different temperature ranges, and the contribution of acoustic deformation potential scattering is negligible over the entire temperature range. Furthermore, the effects of concentrations of shallow donors and deep acceptors on the temperature characteristic curves of mobility and resistivity, the peak mobility and its corresponding temperature (peak temperature), and the mobility and resistivity at room temperature are discussed. Our simulation shows the calculation results agree very well with the reported experimental and theoretical results when the Fe-related level is selected as 0.58 eV below the conduction band edge. Understanding of thermal properties of dark resistivity and mobility can be useful for optimizing GaN:Fe-based electronic and photonic devices performance in different temperature regimes.

Solar Cells on Multicrystalline Silicon Thin Films Converted from Low‐Cost Soda‐Lime Glass

AbstractFabrication and characterization of solar cells based on multicrystalline silicon (mc‐Si) thin films are described and synthesized from low‐cost soda‐lime glass (SLG). The aluminothermic redox reaction of the silicon oxide in SLG during low‐temperature annealing at 600 – 650 °C leads to an mc‐Si thin film with large grains of lateral dimensions in the millimeter range, and moderate p‐type conductivity with an average Al acceptor concentration between 5 × 1016 and 1.2 × 1017 cm−3 in the bulk. A residual composite layer of mainly alumina and unreacted Al forms beneath the mc‐Si thin film as the second product of the crystalline silicon synthesis (CSS) process, which can be used as rear contact in a vertical solar cell design. The mc‐Si absorber (≈10 µm) is thin enough that the diffusion length given by a minority carrier lifetime of ≈1 µs exceeds the path length to the top contact several times. Homojunction and heterojunction diodes have been fabricated on the mc‐Si thin films and show great potential of CSS for the realization of high‐performance solar cells.

C60/CZTS Junction Combination to Improve the Efficiency of CZTS-Based Heterostructure Solar Cells: A Numerical Approach

This work presents a copper zinc tin sulfide (CZTS)-based solar cell structure (AI/ITO/C60/CZTS/SnS/Pt) with C60 as a buffer layer, developed using the SCAPS-1D simulator by optimizing each parameter to calculate the output. Optimizing the parameters, the acceptor concentration and thickness were altered from 6.0 × 1015 cm−3 to 6.0 × 1018 cm−3 and 1500 nm to 3000 nm, respectively. Although, in this simulator, we can tune the value for the acceptor concentration to 6.0 × 1022, higher doping might present an issue regarding adjustment in the physical experiment. Thus, tunable parameters need to be chosen according to the reliability of the experimental work. The defect density varied from 1.0 × 1014 cm−3 to 1.0 × 1017 cm−3 and the auger hole/electron capture coefficient was determined to be 1.0 × 10−26 cm6 s−1 for the maintenance of the minorities in theoretical to quasi-proper experimental measurements. Although the temperature was intended to be kept near room temperature, this parameter was varied from 290 K to 475 K to investigate the effects of the temperature on this cell. The optimization of the proposed structure resulted in a final acceptor concentration of 6.0 × 1018 cm−3 and a thickness of 3000 nm at a defect density of 1.0 × 1015 cm−3, which will help to satisfy the desired experimental performance. Satisfactory outcomes (VOC = 1.24 V, JSC = 27.03 mA/cm2, FF = 89.96%, η = 30.18%) were found compared to the previous analysis.

Interface traps in the sub-3 nm technology node: A comprehensive analysis and benchmarking of negative capacitance FinFET and nanosheet FETs - A reliability perspective from device to circuit level

Interface traps play a significant role in shaping the performance and reliability of semiconductor devices, particularly in advanced technologies such as Negative Capacitance based FinFET and Nanosheet (NS) FET. Hence, for the first time, using well calibrated TCAD models, we benchmark and explore into the analysis of interface traps in NC-FinFET and NC-NSFET devices at the sub-3 nm technology node, focusing on their effects on digital, analog/RF performance parameters. The investigation is mainly focussed on: (a) Positioning of acceptor (EV + 1 - EV-0.4) and donor (EC + 0.2 - EC-1.5) trap locations in the energy band (b) variation in acceptor and donor interface trap concentration (c) design of Common Source (CS) amplifier for analog integrated circuits. In addition, we explored a design space to achieve optimal capacitance matching, targeting the NC effect for an optimized device design. Our findings showed a significant improvement in ION/IOFF ratio by ~9× for NC-NSFET when compared to NC-FinFET with change in acceptor trap locations. The NC-FinFETs demonstrated a resilient intrinsic gain (AV) profile, making them suitable for high-speed amplifiers. Varying donor trap locations had minimal impact on NC-NSFET but slightly affected NC-FinFET's intrinsic gain profile. Moreover, increasing acceptor trap concentration improved digital performance, with NC-NSFET outperforming NC-FinFET and the analog/RF performance favored lower trap concentrations. In addition, NC-FinFETs were more resilient to increased donor traps concentration than NC-NSFETs. Further, the CS amplifier-based NC acceptor devices offered effective amplification and power-saving features, making them ideal for IoT and biomedical applications reliant on battery voltages.

Optimized batch cultivation and scale-up of Bacillus thuringiensis for high-yield production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Addition of statistically optimized concentration of electron acceptor, propionic acid (1.2 g/L) at different cultivation times (0 h, 14.86 h and 19 h) during batch cultivation of B. thuringiensis in mixed substrate (glucose and glycerol) featured production of 8 g/L of biomass and 3.57 g/L of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) containing 0.805 g/L of 3-hydroxyvalerate concentration. Successful scale up of batch cultivation from 7 L to a 70 L bioreactor was, thereafter, achieved using power/volume (P/V) criteria with maximum PHBV and biomass concentration of 3.57 g/L and 7.15 g/L respectively. Characterization of PHBV so produced was carried out using NMR, FTIR, DSC and TGA to elucidate its structure, thermal properties and stability to map their applications in society. These findings highlight the potential of the optimized batch cultivation and scale-up process in producing PHBV emphasizing its relevance in sustainable biopolymer production.

Investigating improvement in the performance of WS2 absorber layer based thin film solar cell with a hole transport layer of Indium Telluride

In this work, Tungsten Disulfide (WS2) is used as absorber layer with Indium Telluride (In2Te3) as hole transport layer and a comparison is made between the devices without and with hole transport layer. Analysis is carried out by varying thickness of WS2, Acceptor concentration of WS2, Interface defects, Temperature, Surface recombination velocities, Series and Shunt Resistances. It is observed that by introducing hole transport layer of Indium Telluride, carrier recombination losses can be restricted and the power conversion efficiency of proposed solar cell can be raised significantly. The efficiency of Tungsten Disulfide absorber layer based solar cell is 23.13% when hole transport layer is not inserted, whereas by incorporating a hole transport layer of Indium Telluride, it is increased to 25.37%. SCAPS-1D is used for simulation of the model.

Tuning Circularly Polarized Afterglow Color via Modulation of Energy and Chirality Transfer in Co‐Doped Films

AbstractCircularly polarized luminescence (CPL) materials offer exciting potential due to their unique light properties. However, controlling the color of afterglow emission, a key feature for many applications remains a challenge. Here, a co‐doping strategy is presented for precise control of multicolor CPL afterglow in films. This approach utilizes chiral naphthylphosphoric acid derivatives as energy and chirality transfer donors, commonly used fluorescent dye rhodamine B (RB) and PVA are selected as the acceptor and the polymeric matrix, respectively. Remarkably, the co‐doped films exhibit ultra‐long green circular polarization phosphorescence lasting several seconds with high efficiency (14.23%), lifetime (1025.5 ms), and dissymmetry factor (8.44 × 10−3). Crucially, by adjusting the acceptor content, it can precisely tune the phosphorescence‐to‐fluorescence ratio and achieve multicolor afterglow. This control stems from a combination of Förster resonance energy transfer, chirality transfer, and color‐mixing effects. Furthermore, this approach significantly improves the asymmetry factor of the CPL afterglow by an order of magnitude (5.17 × 10−2). It is anticipated that this straightforward approach to precisely regulating the afterglow color of CPL will provide invaluable insights for the future design of highly efficient and innovative CPL materials.

The development of a bilayer absorption scenario of CsPbI3/Cs2SnI6 PSCs for enhanced efficiency and stability

The introduction of heterojunction structures in perovskite solar cells (PSCs) can lead to substantial enhancements in power conversion efficiency (PCE) and stability. Using the SCAPS-1D software, we have theoretically investigated the performance potential of CsPbI3/Cs2SnI6 heterojunction PSCs. The purpose of incorporating a thin layer of Cs2SnI6 perovskite onto the CsPbI3 layer is to enhance the stability of the device through the formation of a protective barrier that prevents the continuous degradation of CsPbI3. The device's overall efficiency was found to be greatly enhanced by meticulously optimizing the acceptor concentration (NA), defect density (Nt), and absorber thickness of CsPbI3. In addition, the influence of various physical parameters such as the operating temperature, the work function of the metal rear contact, and series and shunt resistance on the photovoltaic performance of the device is comprehensively examined. With the systematic optimization of these parameters, the device exhibited improved performance and attained an outstanding PCE of 20.86 %, an open circuit voltage (VOC) of 1.19 V, a fill factor (FF) of 81.77%, and a current density voltage (JSC) of 21.32 mA/cm2. We think that our work will provide theoretical guidance in the advancement of heterojunction devices with much improved efficiency and stability.

Characterizing parameter variations for enhanced performance and adaptability in 3 nm MBCFET technology

With the continuous scaling down of semiconductor devices, traditional transistor architectures face significant challenges in maintaining performance and power efficiency. Multi-bridge channel field-effect transistors (MBCFETs) are promising candidates for next-generation of transistors, enabling significant size reduction while preserving high performance. This paper investigates both n-type and p-type 3-nm MBCFETs with a focus on their behavior under diverse operating conditions. The study examines the influence of doping concentration, sheet thickness, temperature, device width, and the number of sheets, on the device's functionality aiming for high-performance applications. Doping concentrations of acceptors and donors ranging from 1 × 10 15 cm−3 - 9 × 10 17 cm−3 and 1 × 10 17 cm−3 - 9 × 10 19 cm−3, respectively, to observe their impact on device performance. Similarly, sheet thicknesses from 1 nm to 2 nm and device widths from 3 nm to 30 nm are analyzed to understand the scaling effects. The temperature varies from 273.15 K to 573.15 K to simulate different operational environments, while the number of sheets, ranging from 1 to 7, is adjusted to evaluate structural effects on device behavior. By extracting the subthreshold swing (SS), threshold voltage (Vth), ON-current (ION), OFF-current (IOFF), and the ION/IOFF ratio, the study offers valuable insights into the suitability and potential applications of N-MBCFET and P-MBCFET devices at the ultra-scaled 3 nm dimension. At room temperatures, the SS achieves 60 mV dec⁻1 for n-type and 64 mV dec⁻1 for p-type which indicates proper switching speed, with corresponding ON/OFF ratios of 2 × 106 and 1 × 105 for n-type and p-type, respectively. This study makes notable contributions to the field of nanoscale transistor technology, aiding in the design and optimization of future electronic devices.

Copper Is Accumulated as Copper Sulfide Particles, and Not Bound to Glutathione, Phytochelatins or Metallothioneins, in the Marine Alga Ulva compressa (Chlorophyta).

To analyze the mechanism of copper accumulation in the marine alga Ulva compressa, it was cultivated with 10 μM of copper, with 10 μM of copper and increasing concentrations of a sulfide donor (NaHS) for 0 to 7 days, and with 10 μM of copper and a concentration of the sulfide acceptor (hypotaurine) for 5 days. The level of intracellular copper was determined as well as the level of glutathione (GSH) and phytochelatins (PCs) and the expression of metallothioneins (UcMTs). The level of intracellular copper in the algae treated with copper increased at day 1, slightly increased until day 5 and remained unchanged until day 7. The level of copper in the algae cultivated with copper and 100 or 200 μM of NaHS continuously increased until day 7 and the copper level was higher in the algae cultivated with 200 μM of NaHS compared to 100 μM of NaHS. In contrast, the level of intracellular copper decreased in the algae treated with copper and hypotaurine. The level of intracellular copper did not correlate with the level of GSH or with the expression of UcMTs, and PCs were not detected in response to copper, or copper and NaHS. Algae treated with copper and with copper and 200 μM of NaHS for 5 days were visualized by TEM and the elemental composition of electrondense particles was analyzed by EDXS. The algae treated with copper showed electrondense particles containing copper and sulfur, but not nitrogen, and they were mainly located in the chloroplast, but also in the cytoplasm. The algae treated with copper and NaHS showed a higher level of electrondense particles containing copper and sulfur, but not nitrogen, and they were located in the chloroplast, and in the cytoplasm. Thus, copper is accumulated as copper sulfide insoluble particles, and not bound to GSH, PCs or UcMTs, in the marine alga U. compressa.

Artificial neural network assisted numerical analysis on performance enhancement of Sb2(S,Se)3 solar cell with SnS as HTL

This paper presents the design and investigation of a highly efficient photovoltaic (PV) device comprising antimony sulfide-selenide (Sb2(S,Se)3) absorber utilizing the SCAPS-1D simulator. Initially, the validity of this simulation process is justified by reproducing the experimental structure, and a comparison is made between the experimental and simulation outcomes. Then we have inserted tin sulfide (SnS) as a hole transport layer (HTL) and zinc sulfide (ZnS) as a buffer at the back and front parts of the suggested new heterojunction structure. In addition, to explore the role of intrinsic parameters on performances of the designed device, an artificial neural network-based machine learning (ML) algorithm is applied. It is revealed that the proposed SnS HTL and ZnS buffer form better band alignment with the promising Sb2(S,Se)3 absorber than others. Thus, the efficiency improves by diminishing recombination loss in the proposed Sb2(S,Se)3 solar device. The PV parameters are also thoroughly assessed by varying crucial factors including absorber thickness, acceptor concentration, defects in absorber, defects at SnS/Sb2(S,Se)3 and Sb2(S,Se)3/ZnS interfaces, temperature, work function, and cell resistances. To achieve the best performances, the thicknesses of HTL, absorber, and buffer are optimized to be 0.1 μm, 1.0 μm, and 0.05 μm, respectively. The simulation predicts an efficiency of 28.20 % accompanied by open-circuit voltage (Voc) of 0.94 V, short-circuit current density (Jsc) of 34.65 mA/cm2, and fill-factor (FF) of 86.22 %. Implementation of ML algorithms uncovers that the predicted performance for both training and testing data is correlated with the actual PCE generated by the SCAPS-1D. The optimized physical parameters derived in this simulation will be very useful for researchers to establish an environmentally friendly, cost-effective, and highly efficient Sb2(S,Se)3-based thin-film PV devices.

Aerobic and anaerobic mineralisation of sediment organic matter in the tidal River Elbe

PurposeThe share of microbially degradable sediment organic matter (SOM) and the degradation rate depend, among others, on the intrinsic properties of SOM as well as on the type and concentration of terminal electron acceptors (TEA). Next to its role as TEA, molecular oxygen enhances SOM decay by oxygenase-mediated breakdown of complex organic molecules. This research investigated long-term SOM decay (> 250 days) under aerobic and anaerobic conditions to (1) provide a basis for sediment carbon flux estimates from the River Elbe estuary and (2) assess the potential for carbon burial in relation to redox conditions and dredging interventions.MethodsLong-term aerobic and anaerobic SOM decay in fluid mud, pre-consolidated and consolidated sediment layers was investigated over three years along a transect of ca. 20 km through the Port of Hamburg, starting at the first hydrodynamically determined hotspot of sedimentation after the weir in Geesthacht. Absolute differences between aerobic and anaerobic cumulative carbon mineralization were calculated, as well as their ratio. Findings were correlated to a suite of solids and pore water properties.ResultsSOM decay followed first order multi-phase exponential decay kinetics. The ratio between C release under aerobic and anaerobic conditions ranged around 4 in the short-term, converging to a value of 2 in the long term. Strong gradients in absolute C release along the upstream–downstream transect did not reflect in a corresponding gradient of the aerobic-anaerobic ratio. C release was most strongly correlated to the water-soluble organic matter, in particular humic acids. Contact of anaerobically stabilized sediment with the oxygenated water phase induced significant release of carbon.ConclusionSOM degradability in the study area exhibited strong spatial gradients in relation to the organic matter source gradient but was mainly limited by the high extent of organic matter stabilization. Under these conditions, molecular oxygen as TEA provides little thermodynamic advantage. Carbon-sensitive sediment management, considering SOM reactivity patterns in stratified depositional areas, is a powerful strategy to reduce environmental impacts of dredging measures.

CH3NH3SnI3${\mathrm{CH}}_{\mathrm{3}}{\mathrm{NH}}_{\mathrm{3}}{\mathrm{SnI}}_{\mathrm{3}}$: Superior Light Absorption and Optimized Device Architecture with 31.93% Efficiency

AbstractThis research investigates and optimizes the perovskite solar cells. Initially, optoelectronic parameters of perovskite absorber materials, including , , and , are estimated using Density Functional Theory (DFT) principles implemented in the Quantum Espresso software. The absorption of light energy is examined, detailing electron transitions between the highest p energy states of halogens (I, Br, and Cl) in the VB and the lowest 5p energy states of tin in the CB. shows superior optical characteristics, surpassing and , and demonstrating more effective absorption within the visible spectrum than . Subsequently, a numerical analysis is conducted for a P–I–N configuration Fluorine doped Tin Oxide (FTO)////Anode using SCAPS‐1D software. The optimization process focuses on absorber thickness, defect density, acceptor density, and the work function (WF) of the anode materials. Simulation findings recommend a defect density () of for optimal performance, coupled with an absorber thickness of 1 µm. Examining the transformation from to through oxidation reveals that reducing the concentration of acceptors in the absorber layer (NA) significantly enhances device performance. Superior performance is achieved by a high WF anode material. This study not only contributes to advancing our understanding of lead‐free perovskite optoelectronics but also provides valuable insights for the development of highly efficient and stable solar cells.

Microbial Ecology and Site Characteristics Underlie Differences in Salinity‐Methane Relationships in Coastal Wetlands

AbstractMethane (CH4) is a potent greenhouse gas emitted by archaea in anaerobic environments such as wetland soils. Tidal freshwater wetlands are predicted to become increasingly saline as sea levels rise due to climate change. Previous work has shown that increases in salinity generally decrease CH4 emissions, but with considerable variation, including instances where salinization increased CH4 flux. We measured microbial community composition, biogeochemistry, and CH4 flux from field samples and lab experiments from four different sites across a wide geographic range. We sought to assess how site differences and microbial ecology affect how CH4 emissions are influenced by salinization. CH4 flux was generally, but not always, positively correlated with CO2 flux, soil carbon, ammonium, phosphate, and pH. Methanogen guilds were positively correlated with CH4 flux across all sites, while methanotroph guilds were both positively and negatively correlated with CH4 depending on site. There was mixed support for negative relationships between CH4 fluxes and concentrations of alternative electron acceptors and abundances of taxa that reduce them. CH4/salinity relationships ranged from negative, to neutral, to positive and appeared to be influenced by site characteristics such as pH and plant composition, which also likely contributed to site differences in microbial communities. The activity of site‐specific microbes that may respond differently to low‐level salinity increases is likely an important driver of CH4/salinity relationships. Our results suggest several factors that make it difficult to generalize CH4/salinity relationships and highlight the need for paired microbial and flux measurements across a broader range of sites.

Performance enhancement of Sb2Se3 solar cell with IGZO and n-ZnO as electron transport layers

A prototype of an antimony (III) selenide (Sb2Se3) solar cell with different electron transport layers (ETLs) was simulated using the Solar Cell Capacitance Simulator (SCAPS) software. The impact of two individual ETLs – namely, indium gallium zinc oxide (IGZO) and n-type zinc oxide (n-ZnO) – was analyzed, and it was found out that n-ZnO was best for the ETL. The n-ZnO, antimony (III) selenide and Indium gallium zinc oxide (IGZO) layers in the newly proposed structure have respective thicknesses of 50, 300 and 20 nm. To achieve the optimum performance of this prototype, the acceptor concentration of copper (II) oxide is taken as 1018 cm−2 and the donor concentration of n-ZnO is taken as 1020 cm−2. The defect densities at antimony (III) selenide and antimony (III) selenide/n-ZnO are taken as 1013 and 1010 cm−2, respectively. They play a crucial part in device performance. With the optimized structure, a maximum power conversion efficiency of up to 31.72% (V OC = 1.148 V, J SC = 48.30 mA/cm2 and fill factor = 88.50%) is obtained with n-ZnO as the ETL. For effective results, the defect densities at both interfaces are taken as 109 cm−2, and maximum efficiency is achieved. Numerical analysis of the proposed structure and study of various parameters such as thickness variation at the absorber layer, series resistance and temperature variation, defect density, metal function and interface density variation were done.

Comprehensive structural and optoelectronic characterizations of co-precipitated Mn-doped SnS nano-powders

This study investigates the physical characteristics of un- and Mn-doped SnS nanoparticles (NPs) synthesized through a co-precipitation method. The undoped SnS is referred to as Mn 0, while Mn 1, Mn 2, and Mn 3 samples are obtained by incorporating 1, 3, and 6 mL of Mn-dopant solution, respectively. Elemental analysis is done by means of energy-dispersive X-ray spectroscopy (EDX), confirming successful Mn incorporation into the SnS lattice. X-ray diffraction (XRD) studies validate the formation of the SnS phase with a preferred orientation at the (040) plane for all samples. The crystallite size (D) of SnS NPs initially increases and then decreases after Mn-doping, confirmed by transmission electron microscopy (TEM) images. Field emission scanning electron microscopy (FESEM) images exhibit grain-shaped morphology with sizes ranging from 23 to 36 nm for all samples. The reduction in bandgap energy (Eg) upon Mn-doping is attributed to variations in grain size and the formation of impurity levels within the SnS band gap. Mott-Schottky analysis showed p-type conductivity for all samples. The semiconductor parameters of SnS, such as the acceptor concentration (NA) and the density of states (NV), improved after Mn-doping. Current-voltage (I–V) curves revealed that the conductivity and mobility of SnS after Mn-doping initially declined for Mn 1 and Mn 2 samples and then improved for the Mn 3 sample. Electrochemical impedance spectroscopy (EIS) results align with the I–V findings. Consequently, it can be concluded that Mn-doping leads to enhancements in optoelectronic properties of SnS.

Kinetics of ferrihydrite reduction in a biofilm system

Microorganisms can exist in both suspended and attached forms in natural and engineered systems. While extensive research has been performed to investigate the bioreduction kinetics of iron oxides by suspended microorganisms, the kinetics of iron oxide reduction by biofilms has not been well studied. This study investigated the rates of ferrihydrite bioreduction by biofilms of Shewanella oneidensis MR-1 with variable concentration ratios of electron donor to acceptor, and different biofilm thickness. Results indicated that the bioreduction rate of ferrihydrite by biofilms increased with increasing biofilm surface area and was faster than that by suspended microorganisms for the same biomass amount, apparently as a result of the biofilm surface area facilitating the direct contact between ferrihydrite and microorganisms for electron transfer. Increasing biofilm thickness decreased bioreduction rate for the same total biomass as a result of the decrease of the ratio of the biofilm surface area to total biomass. The bioreduction rate increased with increasing electron donor and ferrihydrite inputs, consistent with the saturation type of kinetic models. The different rates of ferrihydrite reduction in the biofilm system resulted in different rates of Fe(II) production as a function of electron donor, acceptor, and biofilm surface area, which in turn affected the type and concentrations of the secondary iron minerals, such as lepidocrocite and goethite. A kinetic model was developed that integrates biofilm surface area, and electron donor and acceptor concentrations that well described the measured rates of ferrihydrite bioreduction. The results emphasized the importance of the biofilm surface area in understanding and modeling iron redox biogeochemistry and iron-related biogeochemical processes.

Investigating the potential of WO3 and WS2 as Cd-free buffer layers in Sb2Se3-Based thin-film solar cells: A numerical study with SCAPS-1D software

In this numerical study, the performance of thin-film solar cells (TFSCs) based on Sb2Se3 with WO3 and WS2 materials as Cd-free buffer layers was investigated using SCAPS-1D software. WO3 and WS2 were chosen for their suitable band gaps, good electrical conductivity, and optical transparency. The proposed solar cell structures, Au/Sb2Se3/WO3/ITO and Au/Sb2Se3/WS2/ITO were theoretically examined, considering various factors such as conduction band offset, absorber and buffer layer thickness, doping concentrations, series and shunt resistances, temperature, activation energy, and C–V characteristic. The conduction band offset at the absorber/buffer interface showed spike-like configurations, with values of 0.38 eV and 0.23 eV for the WO3 and WS2 buffer layers, respectively. The optimized thickness for the absorber layer in both structures was 1 μm, while for WO3 and WS2 buffer layers, it was 0.1 μm and 0.05 μm, respectively. The optimized acceptor and donor doping concentrations were 1 × 1016 cm−3 and 1 × 1018 cm−3, respectively. The efficiency of the proposed photovoltaic devices was found to be 9.538 % (with Voc = 0.561 V, Jsc = 30.856 mA/cm2, FF = 55.84 %) and 10.151 % (with Voc = 0.558 V, Jsc = 29.189 mA/cm2, FF = 62.34 %) for structures with WO3 and WS2 buffer layers, respectively. These results suggest that using non-toxic materials like WO3 and WS2 as buffer layers can be an efficient and environmentally friendly alternative to toxic CdS for fabricating cost-effective and highly efficient Sb2Se3-based TFSCs.