Tunable Band Gap Research Articles

Effect of lead and zinc composition on the optical and structural characteristics of PbZnS thin films fabricated by spray pyrolysis

In this study, PbZnS thin films with varying concentrations of lead (Pb) and zinc (Zn) were successfully produced using the spray pyrolysis method. The structural, optical and surface properties of the films were systematically investigated as a function of the Pb/Zn ratio. Xray diffraction (XRD) analysis confirmed the polycrystalline nature of the films, showing a cubic zinc blende structure with improved crystallinity as Pb content increased. Initially, with the increase in Pb concentration, larger crystallite sizes and decreased microstress were observed, but with the increase of Pb addition, the formation of secondary phases and the emergence of lattice distortions caused a decrease in grain size and an increase in microstress. Optical measurements showed a tunable bandgap in the range of 3.25 eV to 1.30 eV as Pb content increased. The narrowing of the bandgap is attributed to the lower energy gap of PbS compared to ZnS, which allows for enhanced absorption of longerwavelength light, especially in the visible and near-infrared regions. These findings highlight the potential of PbZnS thin films for optoelectronic applications, where the ability to tune the bandgap and enhance absorption through compositional adjustments is crucial for optimizing device performance. The surface morphology of the PbZnS thin films was analyzed using scanning electron microscopy (SEM). The SEM images showed notable changes in grain size and surface roughness as Pb content increased, with larger grains and a more distinct surface structure observed in films with higher Pb concentrations. This work demonstrates the versatility of spray pyrolysis in fabricating thin films with controllable properties, offering valuable insights for future applications in energy conversion technologies, including solar cells and photodetectors.

2D WS2 monolayer preparation method and research progress in the field of optoelectronics.

Two-dimensional Transition Metal Dichalcogenides (2D TMDs) have garnered significant attention in the field of materials science due to their remarkable electronic and optoelectronic properties, including high carrier mobility and tunable band gaps. Despite the extensive research on various TMDs, there remains a notable gap in understanding the synthesis techniques and their implications for the practical application of monolayer tungsten disulfide (WS2) in optoelectronic devices. This gap is critical, as the successful integration of WS2 into commercial technologies hinges on the development of reliable synthesis methods that ensure high quality and uniformity of the material. In this study, we present a comprehensive overview of the synthesis techniques for monolayer WS2, focusing on mechanical stripping, Atomic Layer Deposition (ALD), and Chemical Vapor Deposition (CVD). We highlight the advantages of each method, such as the uniform growth achievable with ALD at low temperatures and the capability of CVD to produce large-area, high-quality monolayers. Additionally, we summarize the performance of WS2 in various electronic and optoelectronic applications, including field-effect transistors (FETs), photodetectors, and logic devices. Our findings indicate that with ongoing advancements in film uniformity, compatibility with existing semiconductor processes, and the long-term stability of WS2-based devices, there is a promising trajectory for the transition of 2D WS2 from laboratory research to practical applications. This work not only addresses the existing gaps in the literature but also underscores the potential of WS2 to significantly impact the future of optoelectronic technologies.&#xD.

Nanostructure engineering for ferroelectric photovoltaics.

Ferroelectric photovoltaics have attracted increasing attention since their discovery in the 1970s, due to their above-bandgap photovoltage and polarized-light-dependent photocurrent. However, their practical applications have been limited by their weak visible light absorption and low photoconductivity. Intrinsic modification of the material, such as bandgap tuning through chemical doping, has proven effective, but usually leads to the degradation of ferroelectricity. Recently, various nanostructures, such as multilayer heterojunctions, nanoparticles, vertically aligned nanocomposites and polar nanoregions, have been developed to enhance photovoltaic performance. These approaches enable the nanoassembly of materials in a lower-dimension manner to optimize the bulk photovoltaic effect whilst effectively preserving or even inducing ferroelectricity. This review highlights the fabrication processes of these emerging ferroelectric nanostructures and evaluates their photovoltaic performance.

Micro-Size Layers Evaluation of CIGSe Solar Cells on Flexible Substrates by Two-Segment Process Improved for Overall Efficiencies

This paper details the enhancement of the optoelectronic properties of Cu-(In, Ga)-Se2 (CIGSe) solar cells through a two-segment process in the ultraviolet (UV)–visible spectral range. These include fine-tuning the DC sputtering power of the absorber layer (ranging from 20 to 40 W at segment I) and thoroughly checking the trace micro-chemistry composition of the absorber layer (CdS, ZnO/CdS, ZnMgO/CdS, and ZnMgO at segment II). After segment I of treatment, the optimal 30 W CIGSe absorber layer (i.e., with a 0.95 CGI ratio) can be obtained, it can be seen that the Cu-rich film exhibits the ability to significantly promote grain growth and can effectively reduce its trap state density. After the segment II process aimed at replacing toxic CdS, the optimal metal alloy (Zn0.9Mg0.1O) composition (buffer layer) achieved the highest conversion efficiency (η) of 8.70%, also emphasizing its role in environmental protection. Especially within the tunable bandgap range (2.48–3.62 eV), the developed overall internal and external quantum efficiency (IQE/EQE) is significantly improved by 13.15% at shorter wavelengths. A photovoltaic (PV) module designed with nine optimal CIGSe cells demonstrated commendable stability. Variation remained within ±5% throughout the 60-day experiment. The PV modules in this study represent a breakthrough benchmark toward a significant advance in the scientific understanding of renewable energy. Furthermore, this research clearly promotes the practical application of PV modules, harmonizes with sustainable goals, and actively contributes to the creation of eco-friendly communities.

Temperature‐Driven Topological Transformations in Prestressed Cellular Metamaterials

AbstractStimuli‐responsive materials are able to alter their physicochemical properties, e.g., shape, color, or stiffness, upon exposure to an external trigger, e.g., heat, light, or humidity, exhibiting environmental adaptability. Their capacity to undergo shape reconfiguration, pattern transformation, and property modulation enables multifunctionality. In this work, two strategies are harnessed, i.e., prestressed assembly and temperature‐dependent stiffness reversal, to introduce a class of temperature‐responsive metamaterials capable of undergoing topological transformations, endowing them with smart functionality. Through a combination of mechanics theory, numerical simulations, and thermomechanical experiments, the physical mechanisms underlying the temperature‐triggered topological transformations leading to pattern switches are first elucidated, and then the insights are leveraged to demonstrate tunable bandgaps and robotic capturers. These findings reveal the attainment of giant negative and positive values of coefficient of thermal expansion, accompanied by isotropic expansion and shrinkage under thermal actuation within a fairly rapid timeframe, below 6 s. The strategy here presented is versatile as it relies on a pair of off‐the‐shelf 3D printable materials, can be up‐ and down‐scaled, and can also be realized through other physical stimuli, e.g., light and moisture, paving the way for use in multifunctional applications, including stimulus‐triggered morphing devices, autonomous sensors and actuators, and reconfigurable soft robots.

Enhanced optical properties of chitosan polymer doped with orange peel dye investigated via UV–Vis and FTIR analysis

The current research aims to determine the impact of orange peel dye (OPD), an eco-friendly addition, on the optical properties of biodegradable polymers. This study investigates the enhancement of optical properties in solid electrolytes based on chitosan (CS) and glycerol, with varying OPD concentrations. UV–Vis-NIR spectroscopy revealed significantly enhanced UV–visible light absorption in the 200–500 nm region and effective UV light blocking. FTIR analysis showed strong interactions between OPDs and the CS matrix, with functional groups such as O–H, C=O, and C=C. UV–Visible spectroscopy indicated a reduction in the optical band gap from 5.11 eV in pure CS to 2.93 eV and 2.84 eV with increasing OPD concentrations, reflecting alterations in the electronic structure and enhanced sub-bandgap states. The refractive index improved from 1.31 in pure CS to 1.54 and 1.62 in the doped electrolytes, attributed to increased optical density and light-harvesting capability. Optical basicity also increased from 1.01 to 1.32, enhancing donor properties. These results suggest that OPD-doped CS solid electrolytes offer enhanced optical properties, making them suitable for optoelectronic and UV-blocking applications due to their tunable band gap, improved polarizability, and enhanced light interaction.

Unveiling a Tunable Moiré Bandgap in Bilayer Graphene/hBN Device by Angle-Resolved Photoemission Spectroscopy.

Over the years, great efforts have been devoted in introducing a sizable and tunable band gap in graphene for its potential application in next-generation electronic devices. The primary challenge in modulating this gap has been the absence of a direct method for observing changes of the band gap in momentum space. In this study, advanced spatial- and angle-resolved photoemission spectroscopy technique is employed to directly visualize the gap formation in bilayer graphene, modulated by both displacement fields and moiré potentials. The application of displacement field via in situ electrostatic gating introduces a sizable and tunable electronic bandgap, proportional to the field strength up to 100 meV. Meanwhile, the moiré potential, induced by aligning the underlying hexagonal boron nitride substrate, extends the bandgap by ≈20 meV. Theoretical calculations effectively capture the experimental observations. This investigation provides a quantitative understanding of how these two mechanisms collaboratively modulate the band gap in bilayer graphene, offering valuable guidance for the design of graphene-based electronic devices.

Halide perovskites, a game changer for future medical imaging technology.

The accurate detection of x-rays enables broad applications in various fields, including medical radiography, safety and security screening, and nondestructive inspection. Medical imaging procedures require the x-ray detection devices operating with low doses and high efficiency to reduce radiation health risks, as well as expect the flexible or wearable ones that offer more comfortable and accurate diagnosis experiences. Recently, halide perovskites have shown promising potential in high-performance, cost-effective x-ray detection owing to their attractive features, such as strong x-ray absorption, high-mobility-lifetime product, tunable bandgap, fast response, as well as low-cost raw materials, facile processing, and excellent flexibility. In this review, we comprehensively summarize the recent advances in halide perovskite x-ray detectors and imaging, focusing on their application potential in medical imaging technology. We highlight the recent demonstrations and optimizations of halide perovskite x-ray detectors and imaging and their application in medical radiography. Finally, we conclude by pointing out the challenges of perovskite x-ray detection devices for the clinical practical applications and by sharing our perspectives on the potential solutions for driving the field forward.

Selenium‐Substitution Strategy for Enhanced Mobility, Tunable Bandgap, and Improved Electrochemical Energy Storage in Semiconducting Conjugated Coordination Polymers

Conjugated coordination polymers (c‐CPs), a novel class of organic‐inorganic hybrid materials, are distinguished by their unique structural characteristics and exceptional charge transport properties. The electronic properties of these materials are critically determined by the constituting coordination atoms, with electron‐rich selenol ligands emerging as promising candidates for constructing high‐mobility semiconducting c‐CPs. Currently, c‐CPs incorporating selenium‐substituted ligands remain scarce. In this study, we successfully synthesized a new tetraseleno‐hydroxyquinone (TSHQ) ligand using a “4+2” design strategy and developed a semiconducting three‐dimensional Ag‐Se coordination polymer, Ag4TSHQ. Ag4TSHQ exhibits room‐temperature electrical conductivity of up to 1.6 S/m and shares the same structural topology as Ag4TTHQ (TTHQ = tetrathiol‐hydroxyquinone), enabling precise bandgap modulation from 0.6 eV to 1.5 eV via a mixed‐ligand approach. Time‐resolved terahertz spectroscopy reveals that the charge mobility of Ag4TSHQ in the dc limit is ~350 cm2/V⋅s, which is twice that of its sulfur counterpart, Ag4TTHQ. Furthermore, our evaluations of their electrochemical energy storage capabilities demonstrate that Ag4TSHQ effectively utilizes its redox potential, achieving a remarkable specific capacitance of up to 340 F/g—significantly outperforming Ag4TTHQ, which has a capacitance of 294 F/g. These findings underscore the potential of selenium‐ligand‐based c‐CPs for optoelectronic applications and energy storage technologies.

Selenium-Substitution Strategy for Enhanced Mobility, Tunable Bandgap, and Improved Electrochemical Energy Storage in Semiconducting Conjugated Coordination Polymers.

Conjugated coordination polymers (c-CPs), a novel class of organic-inorganic hybrid materials, are distinguished by their unique structural characteristics and exceptional charge transport properties. The electronic properties of these materials are critically determined by the constituting coordination atoms, with electron-rich selenol ligands emerging as promising candidates for constructing high-mobility semiconducting c-CPs. Currently,c-CPs incorporating selenium-substituted ligands remain scarce. In this study, we successfully synthesized a new tetraseleno-hydroxyquinone (TSHQ) ligand using a "4+2" design strategy and developed a semiconducting three-dimensional Ag-Se coordination polymer, Ag4TSHQ. Ag4TSHQ exhibits room-temperature electrical conductivity of up to 1.6 S/m and shares the same structural topology as Ag4TTHQ (TTHQ = tetrathiol-hydroxyquinone), enabling precise bandgap modulation from 0.6 eV to 1.5 eV via a mixed-ligand approach. Time-resolved terahertz spectroscopy reveals that the charge mobility of Ag4TSHQ in the dc limit is ~350 cm2/V⋅s, which is twice that of its sulfur counterpart, Ag4TTHQ. Furthermore, our evaluations of their electrochemical energy storage capabilities demonstrate that Ag4TSHQ effectively utilizes its redox potential, achieving a remarkable specific capacitance of up to 340 F/g-significantly outperforming Ag4TTHQ, which has a capacitance of 294 F/g. These findings underscore the potential of selenium-ligand-based c-CPs for optoelectronic applications and energy storage technologies.

Improvement of Lead-Free Bismuth Based Perovskite Solar Cell Efficiency with Graded Bandgap Structure

Lead (Pb) halide perovskite has been identified as a promising light-harvesting material for perovskite solar cells (PSCs) with power conversion efficiency (PCE) exceeding 26%. However, the toxicity of Pb-based materials and poisonous environment are the main hindrances that limit their reliable applications. Bismuth (Bi)-based perovskite has shown high potential to replace conventional Pb-based perovskite, but the PCE of Bi-based perovskite solar cells is far lower than Pb-based. Despite the early exploration of Bi-based materials, a fundamental understanding of the material properties and developing strategies, including device design to improve performance, are needed immediately. Here, we report the graded bandgap design for Bi-halide PSCs, which aims to enhance the output current and PCE by maximizing the solar spectrum through device architecture. Titanium dioxide (TiO2) was used as an electron transport layer (ETL), and Spiro-OMeTAD was used as a hole transport layer (HTL) due to its facile implementation and high performance in electronic devices. The variation of iodine concentration in bi-doped iodide sets up bandgap tuning and the conductivity type of the layer. This conFigureuration produces cells with desirable performance that effectively absorb the photons in almost all parts of the solar spectrum. Both open circuit voltage (Voc) (940 mV) and fill factors (~58%) for the best cells have shown drastic improvement over single active layer device, and the short current densities (Jsc) measured are in the range (20-30) mAcm-2. The effects of quasi-electric fields instigated by the graded bandgap structure in the active layers upon the illumination current density and open-circuit voltage of a solar cell will be discussed further.

Ten Years of Perovskite Lasers.

Over the past decade, semiconducting halide perovskite lasers have emerged as a transformative platform in optoelectronics, owing to unique properties such as high photoluminescence quantum yields, tunable bandgaps, and low-cost fabrication processes. This review systematically examines the advancements in halide perovskite lasers, covering diverse laser architectures, such as whispering gallery mode, Fabry-Pérot, plasmonic, bound states in the continuum (BIC), quantum dot, and polariton lasers. The mechanisms of optical gain, the role of material engineering in optimizing lasing performance, and the challenges associated with continuous-wave (CW) pumping and electrically driven lasing are discussed. Furthermore, recent progress in improving the stability and scalability of perovskite lasers, essential for their integration into practical applications in displays, optical communications, sensing, and integrated photonics is highlighted. Finally, future research directions are discussed, emphasizing the potential of perovskite lasers to revolutionize various technological domains by enabling the development of next-generation photonic devices.

Reversible phase transition and tunable band gap in zinc telluride induced by acoustic shock exposure.

In this study, Zinc Telluride (ZnTe) was subjected to acoustic shock waves with a Mach number of 1.5, transient pressure of 0.59 MPa, and a temperature of 520 K to analyze its stability against shock wave impact. ZnTe was exposed to different shock pulses, such as 100, 200, 300, and 400. The stability was assessed through multiple characterization techniques such as Powder X-ray diffraction (PXRD), Raman spectroscopy, Ultraviolet diffuse reflectance spectroscopy (UV-DRS) analysis, Photoluminescence (PL) spectroscopy, and Scanning Electron Microscopy (SEM). The X-ray diffraction pattern revealed a phase transition at 300 shock pulses from cubic (F4̄3m) to cubic (Fm3̄m). Interestingly, at 400 shock pulses, the original cubic (F4̄3m) phase was restored. The Raman spectrum showed the disappearance, intensity variation, and shift of Raman peaks, particularly at 300 shock pulses, which reverted to the original state at 400 pulses, indicating a reversible phase transition. The absorption spectrum exhibited a lower angle shift and a change in band gap from 2.85 eV to 2.63 eV at 300 shock pulses. However, the band gap was reduced to 2.8 eV at 400 shock pulses. The photoluminescence spectrum showed high intensity specifically at 300 shock-loaded conditions. Morphological analysis revealed a change from irregular shapes to plate-like structures at 300 shock pulses. The results confirm that shock waves significantly impact ZnTe, inducing a reversible phase transition.

Effect of growth dynamics on the structural, photophysical and pseudocapacitance properties of famatinite copper antimony sulphide colloidal nanostructures (including nanosheets).

Facile phase selective synthesis of copper antimony sulphide (CAS) nanostructures is important because of their tunable photoconductive and electrochemical properties. In this study, off-stoichiometric famatinite phase CAS (fCAS) quasi-spherical and quasi-hexagonal colloidal nanostructures (including nanosheets) of sizes, 2.4-18.0 nm were grown under variable conditions of temperature (60-200 °C), time and oleylamine capping ligand concentration using copper(II) acetylacetonate and antimony(III) diethyldithiocarbamate precursors. Data from powder X-ray diffraction, Raman spectroscopy and high-resolution scanning/transmission electron microscopy confirm the tetragonal structure of the famatinite phase. X-ray photoelectron spectroscopy, transmission electron microscopy and scanning electron microscopy-energy dispersive X-ray spectroscopy data suggest a correlation of particle size, morphology and composition of the off-stoichiometric fCAS nanostructures with growth temperature and time, and oleylamine concentration. The off-stoichiometric Cu3-aSb1+bS4±c (a, b, c - mole fractions) nanostructures being severely copper-deficient and antimony-rich, exhibit shallow-lying acceptor copper vacancy states, deep-lying donor states of antimony interstitials, sulphur vacancies and antimony-copper antisites and shallow-lying acceptor surface trapping states. These electronic states are likely implicated in tunable UV-visible absorption and bandgaps between 2.3 and 2.8 eV, and broad visible-NIR photoluminescence with fast recombination of radiative lifetimes between 0.2 and 6.2 ns, confirmed from absorption, steady-state and time-resolved photoluminescence spectroscopies. Additionally, cyclic voltammetry and electrochemical impedance spectroscopy confirm that electrodes of the fCAS nanostructures display slightly variable pseudocapacitance of charge-storage primarily via possible sodium ion intercalation with a high specific capacitance of ∼84 F g-1 obtained at a scan rate of 5 mV s-1. Overall, these results show the influence of composition, in particular point defects, phase quality and morphology on the optical and pseudocapacitance properties of fCAS nanostructures, suitable as solar absorbers or electrodes for energy storage devices.

Evaluation of Physicochemical Properties of Cadmium Oxide (CdO)-Incorporated Indium–Tin Oxide (ITO) Nanoparticles for Photocatalysis

This study investigates the structural, optical, and photocatalytic properties of cadmium oxide (CdO) nanoparticles (NPs) and indium–tin oxide (ITO)-doped CdO NPs. The synthesis of CdO NPs and ITO NPs was accomplished through the co-precipitation method. Scanning electron microscopy (SEM) analysis indicates that pure CdO NPs exhibit agglomerated structures, whereas ITO doping introduces porosity and roughness, thereby improving particle dispersion and facilitating electron transport. Energy dispersive spectroscopy (EDS) corroborates the successful incorporation of tin (Sn) and indium (In) within indium–tin oxide (ITO)-doped cadmium oxide (CdO) nanoparticles (NPs) in addition to cadmium (Cd) and oxygen (O). X-ray diffraction (XRD) analysis demonstrates that an increase in ITO doping results in a reduction of the crystallite size, decreasing from 23.43 nm for pure CdO to 18.42 nm at a 10% doping concentration, which can be attributed to lattice distortion. Simultaneously, the band gap exhibits a narrowing from 2.92 eV to 2.52 eV, achieving an optimal value at 10% ITO doping before experiencing a slight increase at higher doping concentrations. This tuneable band gap improves light absorption, which is crucial for photocatalysis. The photocatalytic degradation of rhodamine B (RhB) highlights the superior efficiency of ITO-doped CdO nanoparticles, achieving a remarkable 94.68% degradation under sunlight within 120 min, up 81.01%, significantly surpassing the performance of pure CdO. The optimal RhB concentration for achieving maximum degradation was determined to be 5 mg/L. This enhanced catalytic activity demonstrates the effectiveness of ITO-doped CdO NPs under both UV and visible light, showcasing their potential for efficient pollutant degradation in sunlight-driven applications.

Topology Design of Soft Phononic Crystals for Tunable Band Gaps: A Deep Learning Approach.

The phononic crystals composed of soft materials have received extensive attention owing to the extraordinary behavior when undergoing large deformations, making it possible to provide tunable band gaps actively. However, the inverse designs of them mainly rely on the gradient-driven or gradient-free optimization schemes, which require sensitivity analysis or cause time-consuming, lacking intelligence and flexibility. To this end, a deep learning-based framework composed of a conditional variational autoencoder and multilayer perceptron is proposed to discover the mapping relation from the band gaps to the topology layout applied with prestress. The nonlinear superelastic neo-Hookean model is employed to describe the constitutive characteristics, based on which the band structures are obtained via the transfer matrix method accompanied with Bloch theory. The results show that the proposed data-driven approach can efficiently and rapidly generate multiple candidates applied with predicted prestress. The band gaps are in accord with each other and also consistent with the prescribed targets, verifying the accuracy and flexibility simultaneously. Furthermore, based on the generalization performance, the design space is deeply exploited to obtain desired soft structures whose stop bands are characterized by wider bandwidth, lower location, and enhanced wave attenuation performance.

Synergistic Improvement of Narrow Bandgap PbS Quantum Dot Solar Cells through Surface Ligand Engineering, Near-Infrared Spectral Matching, and Enhanced Electrode Transparency.

The tunability of the energy bandgap in the near-infrared (NIR) range uniquely positions colloidal lead sulfide (PbS) quantum dots (QDs) as a versatile material to enhance the performance of existing perovskite and silicon solar cells in tandem architectures. The desired narrow bandgap (NBG) PbS QDs exhibit polar (111) and nonpolar (100) terminal facets, making effective surface passivation through ligand engineering highly challenging. Despite recent breakthroughs in surface ligand engineering, NBG PbS QDs suffer from uncontrolled agglomeration in solid films, leading to increased energy disorder and trap formation. The limited NIR transparency of commonly used indium-doped tin oxide (ITO) electrodes and inadequate NIR radiation from commercially available solar simulators further compromise the true performance of NBG PbS QDs in solar cells. Here, we employ a hybrid ligand strategy based on inorganic cadmium halide and organic thiol molecules, leading to the partial substitution of surface Pb atoms with Cd heteroatoms. This hybrid ligand strategy substantially reduces undesired QD fusion in solid films, improving the photophysical and electronic properties. By modulating the thickness of the ITO layer and managing refraction loss through a ZnO layer coating, we improved NIR transparency to above 80%. We combine an NIR light source with a solar simulator to achieve near-ideal spectral matching for a broader range with standard AM1.5G illumination. Enhancements in surface passivation of QDs, improvements in NIR transparency of electrodes, and a spectral matched light source setup help us achieve solar cell power conversion efficiencies of 12.4%, 4.48%, and 1.37% under AM 1.5G, perovskite filter, and silicon filter illuminations, respectively. A record open-circuit voltage (Voc) of 0.54 V and short-circuit current density (Jsc) of 38.5 mA/cm2 are achieved under AM 1.5G illumination. We attribute these advancements in photovoltaic parameters to the reduction in Urbach tail states and intermediate trap density originating from superior surface passivation of QDs.

Efficient hole extraction by doped-polyaniline/graphene oxide in lead-free perovskite solar cell: a computational study

Abstract The intriguing behavior of doped polyanilinine/graphene oxide (PANI/GO) offers a solution to the pivotal problem of device stability against moisture in perovskite solar cell (PSC). Tunable bandgap formation of doped PANI/GO with an absorber layer allows effective flexibility for charge carrier conduction and reduced series resistance further boosting the cell performance. Herein, the L9 Orthogonal Array (OA) Taguchi-based grey relational analysis (GRA) optimization was introduced to intensify the key output responses. Furthermore, this work also delved into incorporating a Pb-free absorber perovskite layer, formamidinium tin triiodide (FASnI3), and concomitantly eluding the environmentally hazardous substance. The numerical optimization supported by statistical analysis is based on experimental data to attain the utmost peak cell efficiency. Taguchi’s L9 OA-based GRA predictive modeling recorded over one-fold enhancement over experimental results, reaching as high as 20.28% power conversion efficiency (PCE). Despite that, the PCE of the structures is severely affected by interface defects at the electron transport layer/absorber (ETL/Abs) vicinity, which is almost zero at merely 1 × 1014 cm−2, manifesting that control measures need to be taken into account. This work deduces the feasibility of ETL/Abs stack structure in replacing the conventional Pb-based perovskite absorber layer, while maximizing the potential use of doped PANI/GO as a hole transport layer (HTL).

Strain manipulation of spin-polarized topological phase in WSe2/CrI3 heterostructure

Here, based on first-principles calculations and topological analysis, we show that the spin-polarized topological phase is present in a van der Waals (vdW) heterostructure WSe2/CrI3. We reveal that magnetism induced by proximity effects in the heterostructure breaks the time-reversal symmetry (TRS) and thus induces gapped topological edge states, exhibiting the TRS-breaking quantum spin Hall (QSH) effect. By applying a stress field, the WSe2/CrI3 heterostructure manifests enhanced spin polarization, Rashba splitting, and tunable bandgap. The TRS-breaking QSH effect observed in the WSe2/CrI3 heterostructure exhibits remarkable robustness against interlayer shearing. The distinct anisotropy associated with in-plane strain provides precise manipulation strategies for bandgap engineering. Notably, in-plane tensile strain can significantly increase the nontrivial bandgap by up to 98 meV, suggesting the magnetic WSe2/CrI3 heterostructure represents an outstanding platform for achieving the TRS-breaking QSH effect at room temperature. Our findings provide a theoretical foundation for the development of low-dissipation spintronic nanodevices.

Enhanced performance and long-term stability of 2D photodetectors through hexagonal boron nitride encapsulation

Two-dimensional (2D) semiconductor materials, such as molybdenum disulfide (MoS2), demonstrate considerable potential for optoelectronic applications, largely due to their atomic thickness, tunable bandgap, and capacity for heterostructure integration. Nevertheless, the development of 2D photodetectors that can achieve high responsivity, a fast response time, and long-term stability remains a significant challenge. The present study is a systematic investigation of the effects of top and bottom encapsulation with hexagonal boron nitride (h-BN) on the performance and stability of 2D photodetectors. By employing a dry transfer process to fabricate a high-quality h-BN/MoS2/h-BN structure, we provide effective protection against environmental degradation. The encapsulated devices exhibited a responsivity increase of one to two orders of magnitude under 532 nm laser illumination, in comparison to those without encapsulation. Additionally, the rise and decay times were markedly reduced, by approximately two orders of magnitude, from 0.538 and 3.43 ms to 23.1 and 99.6 μs, respectively. Moreover, the devices demonstrated sustained performance over a 60-day storage period, with response times remaining faster than pre-encapsulation levels. This study highlights the potential of h-BN encapsulation for enhancing both the performance and stability of 2D photodetectors, advancing the development of more reliable optoelectronic devices.