Electron-hole Pair Generation Research Articles

Giant Colloidal Quantum Dot/α-Ga2O3 Heterojunction for High Performance UV-Vis-IR Broadband Photodetector.

Broadband optoelectronics, which extend from the UV to IR regions, are crucial for imaging, autonomous driving, and object recognition. In particular, photon detection efficiency relies significantly on semiconductor properties, such as absorption coefficients and electron-hole pair generation rate, which can be optimized by designing a suitable p-n junction. In this study, we devise giant PbS colloidal quantum dots (G-PbS CQDs) that exhibit high absorption coefficients and broadband absorption. To leverage these exceptional optical properties, we combine G-PbS CQDs with an ultrawide-bandgap semiconductor, α-Ga2O3, and create an efficient G-PbS CQD/α-Ga2O3 heterojunction photodetector that exhibits high performance across the UVC-vis-NIR spectrum range. The resultant heterojunction facilitates efficient electron-hole pair separation at the G-PbS CQD/α-Ga2O3 heterojunction. Furthermore, we utilize transparent graphene electrodes to overcome the limitations of conventional transistor-type device structures and the substantial optical losses induced by opaque metal electrodes. This strategy maximizes the light-collection area and results in an approximately 3-orders of magnitude higher responsivity (55.5 A/W) and specific detectivity (1.66 × 1013 Jones) compared to devices with opaque metal electrodes.

Efficient photodegradation of acid orange 7 in water using a facile ultrasound-assisted microwave-combustion synthesized Ag-ZnAl2-xFexO4 solid-solution photocatalyst

This study explores the development of Ag-ZnAl2-xFexO4 solid-solution photocatalysts for Acid Orange 7 (AO7) degradation under visible light irradiation. The microwave auto-combustion method was employed to synthesize these photocatalysts, allowing for the investigation of the influence of Fe substitution (x) on their properties and performance. Characterization techniques revealed a trade-off between Fe content, surface area, pore size, and light absorption capacity. The Ag-ZnAlFeO4 variant achieved an optimal balance, demonstrating exceptional photocatalytic activity for AO7 degradation. This optimized photocatalyst achieved a removal efficiency of 99.3 % under neutral pH conditions, highlighting its effectiveness and potential for practical applications. Interestingly, the mineralization efficiency of AO7 reached 85.2 % after 160 minutes of reaction time. Kinetic studies supported the superior performance of Ag-ZnAlFeO4, attributing its success to its favorable morphology, high surface area, strong light absorption, and minimal electron-hole pair recombination. The proposed degradation mechanism involves light absorption, generation of electron-hole pairs, and their subsequent reactions with water and oxygen molecules to degrade AO7. This work establishes Ag-ZnAl2-xFexO4, particularly Ag-ZnAlFeO4, as a promising visible-light photocatalyst for the efficient degradation of organic pollutants.

Transient Current Analysis of GaN Neutron Detector Based on the SRIM and TCAD Methods

Utilizing Technology Computer Aided Design (TCAD) software, this study determines the optimal thickness and doping concentration for the intrinsic gallium nitride (GaN) layer in a p-i-n GaN diode to improve detection efficiency and reliability. The study examines energy loss and the transient current response induced by alpha and 3H particles within the GaN p-i-n diode. Additionally, TCAD elucidates the transient current behavior arising from electron-hole pair generation, utilizing the Stopping and Range of Ions in Matter SRIM-2013 linear energy transfer distribution as a guide. The simulations disclose that the tailing effect in the transient current response results from radiation-induced hole accumulation. Elevated applied bias results in increased transient current pulse amplitude, attributed to an extended depletion region that boosts carrier collection. These insights are expected to drive advancements in GaN-based neutron detector technology, essential for advancing nuclear and space science applications in the next generation.

Performance study of GaN-based betavoltaic nuclear batteries with 3D interfaces

This study presents a design of a 3D interface simulation model featuring an inverted pyramid structure. Our objective is to forecast the performance of GaN-based betavoltaic nuclear batteries with the PN junction 3D interface structures comparing a practical machining process. Initially, we computed the electron-hole pairs (EHPs) generation rate in GaN materials irradiated by both 63Ni and 147Pm sources using Geant4. Furthermore, we employed COMSOL Multiphysics, a finite element analysis software, to simulate the EHPs transport phenomena within the battery and investigate the influence of structural parameters on the output performance. Despite maintaining thicknesses of the P- and N-regions and consistent doping concentrations (Hp-GaN, Hn-GaN, Na, and Nd) as constants, the simulation results revealed notable disparities in the short-circuit current density (Jsc), open-circuit voltage (Voc), and maximum output power density (Pmax) among batteries irradiated with various radioactive sources. Subsequently, we investigated the output performance of the nuclear battery by altering parameters such as the number of inverted pyramid structures, junction depth, and type of radioactive source. Our investigation revealed that selecting 63Ni as the radioactive source, with Na at 1017 cm−3, Nd at 1014 cm−3, a junction depth of 0.1 μm, and inverted pyramid structures of 25, resulted in the following battery performance parameters: a short-circuit current density (Jsc) of 0.648 μA/cm2, an open-circuit voltage (Voc) of 2.3481 V, and a maximum output power density (Pmax) of 1.2949 μW/cm2. Substituting the radioactive source with 147Pm, the average short-circuit current density, Jsc, increased to 56.865 μA/cm2, and the maximum output power density, Pmax, increased to 94.975 μW/cm2, It's a significant enhancement in output performance.

A Spin‐Polarized Electron‐Induced MXene‐KBi0.9Co0.1Fe2O5 Photocatalyst for Enhanced Dye Degradation

In photocatalysts aimed to degrade environmental pollutants, photons are generally used as primary stimuli to generate electron–hole pairs to target the chemical bonds to disintegrate. Recently, electron spin has been reported as an essential degree of freedom to improve the performance of photocatalysts. In this work, spin‐polarized electrons and holes are introduced into a brownmillerite KBi0.9Co0.1Fe2O5 semiconductor and a two‐dimensional (2D) MXene composite system by application of an external magnetic field. The spin polarization properties are monitored by measuring the magnetoresistance effect of the MXene‐KBCFO device, which is related to the carrier transfer efficiency. Remarkably, the photocatalytic performance of MXene‐KBCFO is significantly enhanced by the simultaneous application of an external magnetic field and illumination due to the increased number of spin‐polarized photoexcited carriers caused by the synergy effect of the 2D MXene heterostructure together with the ferromagnetic spin ordering. This results in increased reaction hotspots, effective built‐in electric field, extended carrier lifetime, and reduced charge recombination owing to parallel alignment of electron spin orientation. The results show that the efficiency and stability of photocatalytic dye degradation can be effectively enhanced by manipulating the spin‐polarized electrons in the MXene‐based oxide‐perovskite heterostructure photocatalyst.

Effect mechanism of Cd on band structure and photocatalytic hydrogen production performance of ZnS

ZnS is widely used in the photocatalytic decomposition of water to produce hydrogen due to its fast electron-hole pair generation and high negative potential. However, its absorption in the visible region is poor due to its wide band gap, and it has serious photogenerated carrier recombination problems. Herein, a shallow impurity energy level was introduced by doping the ZnS lattice with Cd. Due to its presence, electrons trying to return to the valence band are trapped and excited twice, suppressing the recombination of photogenerated carriers and greatly improving electron utilization. The Cd1.5-ZnS possesses a hydrogen production rate as high as 85722.20 μmol/g, which is 17 times higher than pure ZnS. Meanwhile, Cd1.5-ZnS has a narrower forbidden band and superior visible light absorption, and the serious photocorrosion problem of ZnS has been suppressed. This study provides a viable approach for the synthesis of photocatalysts with adjustable band gaps and enhanced hydrogen precipitation efficiency.

Photoactivation of sulfite by FeTiO3 for organic pollutant degradation: Performance and mechanism

In recent years, the exploration of sulfite (S(IV))-based advanced oxidation processes has attracted increasing attention due to its high performance in the degradation of aqueous organic contaminants. In this study, we investigated the activation of S(IV) by ilmenite (FeTiO3) under photo irradiation using phenol as a substrate. The FeTiO3/S(IV)/photo system demonstrated a remarkable phenol removal rate, achieving 81.4 % degradation within 30 min under optimal conditions. The photocatalytic mechanism involves the generation of electron-hole pairs in FeTiO3, with photogenerated holes activating the adsorbed S(IV) on the catalyst’s surface to produce various free radicals, among which SO4− is identified as the primary active species. Density functional theory calculations further suggest that electron transfer between ilmenite and S(IV) may occur via a Fe-O-S bridge. Additionally, the approach demonstrates satisfactory reusability of the photocatalyst and consistent effectiveness in real-water matrices. This study contributes to the development of more efficient, cost-effective, and environmentally friendly water treatment strategies by providing a deeper understanding of the proposed FeTiO3/S(IV)/photo system.

(Invited) MoS2 Photodetectors for Near-Infrared Biosensing Applications

Device researchers have been actively developing novel diagnostic biosensors using metallic nanoparticle-based plasmonic immunoassays.[1] In these biosensing devices, photodetectors with high photoresponsivity and low internal noise levels are integrated to detect the marginal optical signals change induced by biomarker binding events (i.e., Antigen-antibody binding). Recently, atomically thin layers of molybdenum disulfide (MoS2) have been integrated with plasmonic components to enable fast and sensitive colorimetric monitoring of disease-related biomarkers.[2] However, such biosensors are mostly operated in the ultraviolet/visible range, which needs a purification step to separate out a variety of unwanted biomaterials that absorb visible light and takes several hours of preparation steps. Thus, it would be amenable to develop biosensors for biomolecular detections or immunoassays in the whole blood (WB) analytes without any sample preparations.[3] To address the issues mentioned above, recent studies have demonstrated the engineered gold nanoparticles (AuNPs) that have localized surface plasmonic resonance (LSPR) shift around near-infrared (NIR) wavelength region. However, a high-sensitivity photodetector under NIR region is still required to detect marginal signal changes due to the target biomarker binding events. Meanwhile, the MoS2 material has been reported to exhibits superior photo-response characteristics.[4] MoS2 is a transition metal dichalcogenide material of which single- and multi-layer films exhibit an efficient electron-hole pair generation rate under photoexcitation and therefore high photo absorption as compared to silicon. Therefore, a systematical study on MoS2 photoconductors to optimize the optoelectronic properties under near-infrared (NIR) (λ = 650 nm) operation can enable zero-preparation WB immunoassays combined with specially engineered AuNPs.In this work, we study the photo-response properties (i.e., Photoresponsivity spectrum) of in-plane MoS2 photodetectors as the function of their geometric dimensions and fabrication conditions. Recent study shows that an annealing temperature after exfoliation can etch the upper layers of MoS2 flakes and clean stains on the device and therefore improve device performances (e.g., mobility). [5] This work enables the NIR operation capabilities of plasmonic colorimetric biosensing by introducing the optimized MoS2 photodetector fabrication practice. This approach reduces assay preparation times and mitigate background interference even with WB analytes and thereby enable the WB point-of-care immunoassays.

Revolutionizing textile wastewater treatment: Enhanced degradation of dyes using bimetallic Zinc Ferrite-GO nanocomposites

A novel bimetallic nickel-copper doped zinc ferrite based catalyst has been synthesized using the hydrothermal method. The nano-sized bimetallic (Ni-Cu) zinc ferrites were embedded with graphene oxide (GO). The characterization of nano-sized bimetallic (Ni-Cu) zinc ferrites with graphene oxide (GO) involves a comprehensive set of analytical techniques to determine their elemental composition, structural properties, and morphological features. The prepared materials were also subjected to structural and morphological evaluation through FTIR, Raman, XRD, TGA, UV–vis spectroscopy, and SEM with EDX. The experiment for the photodegradation of the selected model pollutant dye, methylene blue was conducted using the prepared materials. This means that the present photocatalyst has a high efficiency of degrading the pollutant to a tune of 99 % within 3 h. When the amount of GO in the prepared nanocomposite was 40 %, there was the perfect result in terms of no degradation of MB. It reduced and deteriorated the degree of band gap energy of the MB dye. The photocatalyst activity was proven to be repeatable; the sample's use was again possible. A decrease in the band gap energy implies that the improved photocatalyst material becomes more efficient at absorbing light energy. This enhanced light absorption promotes the generation of electron-hole pairs, which are essential for catalytic reactions. Therefore, the reduction in band gap energy likely contributes to the catalyst's heightened ability to initiate the degradation of the MB dye, ultimately leading to more effective pollutant removal. In the future, the synthesized sample can be reused without significant loss in its catalytic efficiency, underscoring the stability and durability of the material. The current study has paramount importance for real-world applications; reliable performance over multiple cycles ensures that the catalyst remains effective in addressing pollution challenges over prolonged periods.

A new 3D Zn(II)‐based MOF with gra topological network as a photocatalyst for antibiotic degradation

A novel zinc‐based metal–organic framework (Zn‐MOF), designated as [Zn3(L)(bpyp)2(HCOO)3·2DMF·H2O] (1), was synthesized using 2,5‐bis(pyrid‐4‐yl)pyridine (bpyp), 1,3,5‐benzenetricarboxylic acid (H3L), and Zn(CH3COO)2·2H2O in a DMF solution. Single‐crystal X‐ray diffraction analysis revealed that MOF 1 crystallizes in the monoclinic system with a C2/c space group, featuring a (3,5)‐connected binodal network. The structural integrity and characteristics of MOF 1 were confirmed by Fourier transform infrared (FT‐IR), thermal gravimetric analysis (TGA), powder X‐ray diffraction (PXRD), and Brunauer–Emmett–Teller (BET) analyses, showing type IV isotherms indicative of microporous structures. The photocatalytic efficiency of MOF 1 was evaluated for the degradation of various antibiotics under UV light, with nitrofurantoin (NFT) demonstrating the highest degradation rate of 83.9% at an optimal concentration of 40 ppm and catalyst loading of 5 mg. The degradation process followed a pseudo‐first‐order kinetic model with a rate constant of 0.02492 min−1. Radical trapping experiments identified superoxide radicals (O2˙−) and holes (h+) as the predominant reactive species, while hydroxyl radicals (˙OH) played a negligible role. Reusability tests over four cycles confirmed the stability and durability of MOF 1, with consistent photocatalytic performance and unchanged structural morphology as evidenced by PXRD and SEM analyses. The proposed mechanism involves photoinduced electron–hole pair generation, with subsequent formation of reactive oxygen species (ROS) facilitating NFT degradation. This study highlights MOF 1 as a promising photocatalyst for environmental remediation, specifically for the efficient degradation of pharmaceutical contaminants in aquatic systems, providing insights into its structural properties, photocatalytic activity, and underlying degradation mechanisms.

Indoor air disinfection by non thermal atmospheric pressure plasma: a comparative study of performance in low and high humidity environments

Atmospheric pressure plasma (APP) has intrigued the interest of researchers for various applications such as disinfection, air purification, etc. In this context, a deeper understanding of the correlation between APP’s characteristics like discharge parameters, active species composition, and eradication of airborne microorganisms with varying relative humidity (RH) has been examined using a dielectric barrier discharge based atmospheric pressure plasma (DBD-APP) source. One of the electrodes of the developed DBD-APP source has been coated with TiO2 nanoparticles to enhance the generation of reactive species during the discharge process. The results show that, even with the same peak-to-peak applied voltage, the peak-to-peak current and discharge power decrease with increasing RH. Optical emission spectroscopy (OES) is used to determine the relative emission intensity of the reactive species, whereas spectrophotometry is used to quantify the reactive species produced by the plasma at various parameters. Instead of UV radiation, the plasma-produced highly energetic electrons activates the TiO2 nanoparticles for electron–hole pair generation. The geometry of the plasma device has played an important role in generating high energy electrons. From the developed DBD-APP source, the airborne microorganism’s disinfection efficiency of ∼95.8% and ∼98.7% has been achieved in the total bacterial counts (TBCs) and total fungal counts (TFCs) at an RH range of 70%–90%, in just 20 min of continuous operation. However, in the RH range of 20%–40%, the inactivation efficiency dropped to ∼78.8% and ∼87.5% for the TBCs and TFCs, respectively. The outcome indicates that higher humidity levels are better for indoor air purification using DBD-APP sources and that plasma with a circulation system can effectively disinfect indoor environments.

Optimum Solar Cell Power Conversion Efficiency-Based Patterned Planar Solar Surface Morphology with Various Solar Cell Absorber Structures

This paper simulated the optimum solar cell power conversion efficiency-based planar solar surface morphology with various solar cell absorber structures. The spectral light intensity, reflected, absorbed, and transmission coefficients versus wavelength band spectrum varied from 300[Formula: see text]nm to 1300[Formula: see text]nm through the visible to near-infrared regions. The optimum solar cell performance parameters or key parameters are studied with different solar cell structure designs based on different surface contact and back contact layers. Cumulative generation current, cumulative electron–hole pair generation rate and electron–hole pair generation rate are clarified versus substrate depth for various solar cell structure designs. The absorbed current in substrate is optimized for various solar cell structure designs. Maximum power voltage and current are also optimized for the proposed solar cell structure design. The effective solar cell power efficiency is also demonstrated based on the optimized maximum power current and maximum power voltage.

Tuning Stark effect by defect engineering on black titanium dioxide mesoporous spheres for enhanced hydrogen evolution

Defects can strongly affect the lattice, strain, and electronic structures of nanomaterials photocatalysts, like a double-edged sword of both positive significance and negative influence on photocatalytic performances. To date, most studies into defects only partially elucidated their beneficial or detrimental roles in photocatalysis. However, a quantitative understanding of the photocatalytic performances modulated by defect concentration still needs to be discovered. Here, a series of TiO2−X mesoporous spheres (MS) with different oxygen vacancy concentrations for photocatalytic applications were prepared by high-temperature chemical reduction. The link between oxygen vacancy concentration and photocatalytic performance was successfully established. The localization of carriers dominated by the Stark effect is first enhanced and then weakened with increasing oxygen vacancy concentration, which is a crucial factor in explaining the double-edged sword role of defect concentration in photocatalysis. As the reduction temperature rises to 300 °C, carrier localization dominated by the quantum-confined Stark effect maximizes the separation ability of photo generated electron hole pairs, thus exhibiting the best catalytic performance for photocatalytic hydrogen production and the degradation of organic pollutants, as demonstrated by a hydrogen evolution rate of 523.7 µmol g-1 h-1 and a ninefold higher RhB photodegradation rate compared to TiO2 MS. The work offers excellent flexibility for precisely constructing high-performance photocatalysts by understanding vacancy engineering.

Enhanced photocatalytic removal of Cr(VI) and Rhodamine B from water using plant-mediated CdS nanoparticles: Mechanistic insights and environmental applications

Photocatalytic remediation using semiconductor nanoparticles presents a promising approach for water purification. In this study, cadmium sulfide (CdS) nanoparticles were synthesized via a plant-mediated approach and evaluated for their efficacy in removing Cr(VI) and Rhodamine B contaminants from aqueous solutions under visible light irradiation. The CdS nanoparticles were characterized by X-ray diffraction (XRD), which confirmed the presence of the cubic phase with a crystallite size of 10 nm. UV–visible diffuse reflectance spectroscopy (DRS) indicated bandgap energy of 2.4 eV, facilitating visible light absorption. Photoluminescence (PL) spectroscopy revealed reduced recombination rates of photogenerated charge carriers, enhancing photocatalytic efficiency. The synthesized CdS nanoparticles demonstrated efficient removal of both Cr(VI) and Rhodamine B, achieving degradation efficiencies of 92 % and 95 %, respectively, within 120 min under optimized conditions. Mechanistic insights suggest the generation of reactive oxygen species (ROS) and electron-hole pairs (e-/h+) contributing to pollutant degradation. This study underscores the potential of plant-mediated CdS nanoparticles as effective photocatalysts for environmental remediation applications.

Facile synthesis of silver doped manganese oxide nanocomposite with superior photocatalytic and antimicrobial activity under visible spectrum

Water pollution and antimicrobial resistance (AMR) have become two global threats; 80% of diseases and 50% of child deaths are due to poor water quality. In this study, hydrothermal processing was employed to manufacture manganese oxide nanorods. Silver dopant was deposited on the surface of manganese oxide. XRD diffractogram confirmed the facile synthesis of Ag/Mn2O3 nanocomposite. XPS survey analysis demonstrated silver content of 9.43 atom %. Photocatalytic measurements demonstrated the outstanding efficiency of the Ag-Mn2O3 compared to virgin oxide particles under visible radiation. Degradation efficiencies Mn2O3 and Ag/Mn2O3 on methyl orange (MO) dye was found to be 53% and 85% under visible spectrum. Silver dopant was found to decrease the binding energy of valence electrons; this action could support electron–hole pair generation under visible spectrum and could promote catalytic performance. Ag/Mn2O3 NPs demonstrated most effective performance (95% removal efficiency) at pH 3; this could be ascribed to the electrostatic attraction between positively charged catalyst and the negatively charged MO. Ag/Mn2O3 demonstrated enhanced antibacterial activity against Gram-positive Staphylococcus aureus (S. aureus) (19 mm ZOI), and Gram-negative Escherichiacoli (E. coli) (22 mm ZOI) respectively; the developed nanocomposite demonstrated advanced anti-film activity with inhibition percentage of 95.5% against E. coli followed by 89.5% against S. aureus.

High-Performance Aqueous Zinc-Organic Battery with a Photo-Responsive Covalent Organic Framework Cathode.

Covalent organic framework (COF) materials, known for their robust porous character, sustainability, and abundance, have great potential as cathodes for aqueous Zn-ion batteries (ZIBs). However, their application is hindered by low reversible capacity and discharge voltage. Herein, a donor-acceptor configuration COF (NT-COF) is utilized as the cathode for ZIBs. The cell exhibits a high discharge voltage plateau of ≈1.4V and a discharge capacity of 214 mAh g-1 at 0.2 A g-1 when utilizing the Mn2+ electrolyte additive in the ZnSO4 electrolyte. A synergistic combination mechanism is proposed, involving the deposition/dissolution reactions of Zn4SO4(OH)6·4H2O and the co-(de)insertion reactions of H+ and SO4 2- in NT-COF. Meanwhile, the NT-COF with a donor-acceptor configuration facilitates efficient generation and separation of electron-hole pairs upon light exposure, thereby enhancing electrochemical reactions within the battery. This leads to a reduction in charging voltage and internal overvoltage, ultimately minimizing electricity consumption. Under ambient weather conditions, the cell exhibits an average discharge capacity of 430 mAh g-1 on sunny days and maintains consistent cycling stability for a duration of 200 cycles (≈19 days) at 0.2 A g-1. This research inspires the advancement of Zn-organic batteries for high-energy-density aqueous electrochemical energy storage systems or photo-electrochemical batteries.

Oxalic Acid-Assisted Photo-Fenton Catalysis Using Magnetic Fe3O4 Nanoparticles for Complete Removal of Textile Dye

Textile industry effluents contain several hazardous substances, such as dye-containing effluents, which pose environmental and aesthetic challenges. Presently, the microbial-based remediation process is in use. This study investigated the application of ferrous–ferric oxide (Fe3O4) nanoparticles, a readily formulated nanoadsorbent, to remove scattered dye molecules from industrial effluents. The ferrous–ferric oxide nanoparticles were prepared using a chemical co-precipitation method. The nanoparticles had 26.93 emu g−1 magnetization, with sizes smaller than 20 nm, and possessed a highly purified cubic spinel crystallite structure. The catalytic activity of the iron oxide depended on the dose, photocatalytic enhancer, i.e., H2O2 level, pH of the reaction medium, and dye concentration. We optimized the Fenton-like reaction to work best using 1.0 g/L of ferrous–ferric oxide nanoparticles, 60 mM oxalic acid at pH 7.0, and 60 ppm of dye. Iron oxides act as photocatalysts, and oxalic acid generates electron–hole pairs. Consequently, higher amounts of super-radicals cause the rapid degradation of dye and pseudo-first-order reactions. Liquid chromatography–mass spectrometry (LC-MS) analysis revealed the ferrous–ferric oxide nanoparticles decolorized and destroyed Disperse Red 277 in 180 min under visible light. Hence, complete demineralization is observed using a photo-Fenton-like reaction within 3 h under visible light. These high-capacity, easy-to-separate next-generation adsorption systems are suggested to be suitable for industrial-scale use. Ferrous–ferric oxide nanoparticles with increased adsorption and magnetic properties could be utilized to clean environmental pollution.

Nonvolatile photoelectric memristor for reconfigurable Boolean logic operation and data storage

Photoelectric memristors have the advantages of highly parallel computing and large-scale interconnection, which provides a promising method for reconfigurable logic operations and greatly promotes the development of new memory computing technology. In this paper, a photoelectric memristor was fabricated using natural gelatin and water-soluble CdSe/ZnS quantum dots with a shell structure. Under light stimulation, the device undergoes photoelectric effects in the dielectric layer, generating electron–hole pairs and causing the device to transition from a high-resistance state to a low-resistance state. Seven nonvolatile logic functions are achieved using three wavelengths of light excitation devices. Compared with traditional electrically controlled memristors, emerging photoelectric memristors are more attractive because they can integrate the advantages of photons and electrons.

Rhodamine B degradation over visible light promoted Bi2WO6/Bi2W0.75Mo0.25O6 and Bi2MoO6/Bi2W0.75Mo0.25O6 heterostructures: DFT and photocatalytic studies

In the recent past, the dye degradation through semiconductor photocatalysis under visible light has drawn the widespread attention. In this view, visible active (1-x)Bi2WO6/xBi2W0.75Mo0.25O6 and (1-x)Bi2MoO6/xBi2W0.75Mo0.25O6 (commonly 0.05 ≤ x ≤ 0.20 wt%) heterostructures prepared through a one-step hydrothermal process. These compounds were analyzed by XRD, FE-SEM, HRTEM, XPS, FT-IR, DFT, UV-Vis DRS and photoluminescence. In (1-x)Bi2WO6/xBi2W0.75Mo0.25O6, the 0.90Bi2WO6/0.10Bi2W0.75Mo0.25O6 heterostructure showed the highest photocatalytic activity in comparison with Bi2WO6 and Bi2W0.75Mo0.25O6. On contrary, all (1-x)Bi2MoO6/xBi2W0.75Mo0.25O6 heterostructures exhibited the less photocatalytic activity than that of Bi2MoO6. The analysis carried out on both heterostructures clearly demonstrated that (1-x)Bi2WO6/xBi2W0.75Mo0.25O6 is more active in comparison to (1-x)Bi2MoO6/xBi2W0.75Mo0.25O6. The radical trapping test was conducted for 0.90Bi2WO6/ 0.10Bi2W0.75Mo0.25O6 heterostructure, asserted that O2∙− and h+radicals were dominant species responsible for Rhodamine B (Rh B) photo-degradation. The estimated redox potentials of Bi2WO6, Bi2W0.75Mo0.25O6 establish the fact that the charge (e-/h+) migration between Bi2WO6 and Bi2W0.75Mo0.25O6 via Z scheme is accountable for the aggressive photocatalytic activity of Bi2WO6/Bi2W0.75Mo0.25O6 heterostructure. The plausible Z scheme mechanism of the generation of electron-hole pairs, charge transfer and also visible light-induced degradation of Rh B was proposed.

Yielding high photovoltaic conversion efficiency by Pd-decoration on Si-based interface: A density-functional theory study

There has been showing great interest in boosting the performance of III-V/Si multi-junction solar cell, which is low-cost and offering high photovoltaic conversion efficiency. Adding noble-metal nano-array at the interface between the Si and III-V materials is one of most effective ways. This theoretical work comprehensively studied the atomic structure, electronic properties, and optical response of Pd-decoration on the Si(111) surface by using density-functional theory calculations. The structural stability calculations showed that Pd atoms could exist on Si surface in many forms. The calculated differential charge density with Bader charge showed that the charge transfer between Pd and Si atoms would increase the generation of electron-hole pairs. At the same time, Pd-decoration could reduce the work function and improve the optical conductivity of Si surface. In addition, the modification of Pd atoms would create new energy levels near the Fermi level in the band gap of Si surface. These energy levels enable Si bottom cell to undergo electron inter-band transitions under weak light irradiation, improving the utilization of weak light. This work provided a micro physical explanation for the improvement of III-V/Si solar cell by using noble-metal nano-array.