Adjustable Band Gap Research Articles

Hafnium-Based Chiral 2D Organic-Inorganic Hybrid Metal Halides: Engineering Polarity and Nonlinear Optical Properties via Para-Substituent Effects.

Two-dimensional (2D) organic-inorganic hybrid metal halides (OIMHs), characterized by noncentrosymmetric structures arising from the incorporation of chiral organic molecules that break inversion symmetry, have attracted significant attention. Particularly, chiral-polar 2D OIMHs offer a unique platform for multifunctional applications, as the coexistence of chirality and polarity enables the simultaneous manifestation of distinct properties such as nonlinear optical (NLO) effects, circular dichroism (CD), and ferroelectricity. In this study, we report the first synthesis of hafnium (Hf)-based chiral 2D OIMHs, achieved through the strategic incorporation of para-substituents on the benzene ring of chiral organic components. By tuning the substituents, we successfully modulate the polarity of the crystal structures, resulting in both chiral-nonpolar and chiral-polar systems. Our analysis of structural and optical properties, supported by density functional theory calculations, demonstrates that the polarity of these materials can be systematically tuned, enabling adjustable band gaps and CD in the UV range (200-280 nm). Notably, halogen substitution at the para-position of the benzene ring in the organic layer produces tunable optical band gaps ranging from 4.33 to 4.48 eV, the widest reported to date for chiral-polar 2D OIMHs. Furthermore, these materials exhibit enhanced NLO properties, including a remarkable 3.3-fold increase in second-harmonic generation intensity in chiral-polar compounds compared to their chiral-nonpolar counterparts. These findings position Hf-based chiral 2D OIMHs as promising candidates for UV-region applications, such as UV NLO devices and self-driven circularly polarized light detectors, offering new opportunities for designing multifunctional optoelectronic materials by harnessing the interplay between chirality and polarity.

A Systematic Analysis of The Current 2D Perovskite Engineering Approach and Future Prospects

Perovskite solar cells (PSCs) have become a hot topic in the photovoltaic studies. Although perovskite has excellent photoelectric properties including adjustable bandgap, high power conversion efficiency (PCE) performance, high electron transport, the three-dimensional perovskite commonly studied is often unstable, short life, and subject to environmental interference especially heat and humidity. So two-dimensional perovskites have been studied and studied. This paper introduces the 2D materials and 2D perovskite solar cells. And then several new works of surface engineering on 2D perovskite solar cells including passivation strategies, interface engineering and orientation of crystallization on perovskite films are mentioned and concluded, thereby providing a future understanding to improve and balance the efficiency and stability of 2D PSCs. Even though the existing strategies for optimizing two-dimensional perovskite are abundant and have certain rules, more essential two-dimensional perovskite properties to improve efficiency and stability need to be studied, so that two-dimensional perovskite will have more possibilities in industrial production.

Numerical evaluation of bi-facial ZnO/MoTe2 photovoltaic solar cells with N-doped Cu2O as the BSF layer for enhancing V OC via device simulation.

Molybdenum telluride (MoTe2) shows great promise as a solar absorber material for photovoltaic (PV) cells owing to its wide absorption range, adjustable bandgap, and lack of dangling bonds at the surface. In this research, a basic device structure comprising Pt/MoTe2/ZnO/ITO/Al was developed, and its potential was assessed using the SCAPS-1D software. The preliminary device exhibited a photovoltaic efficiency of 23.87%. The integration of a 100 nm thick nitrogen-doped copper oxide (N-doped Cu2O) layer as a hole transport/BSF layer improved the device performance of the MoTe2/ZnO photovoltaic solar cell (PVSC), increasing the open circuit voltage (V OC) from 0.68 V to 1.00 V and, consequently, its efficiency from 23.87% to 34.45%. Recombination and C-V analyses were conducted across various regions of the device with and without the BSF layer. The results of these analyses revealed that this improvement in the device performance mainly stemmed from a decrease in recombination losses at the absorber/BSF interface and an increase in the built-in potential of the device, resulting in improved V OC and photovoltaic efficiency. Additionally, the performance of the device in a bifacial mode was studied. The calculated bifacial factor (BF) values suggested that there were negligible additional losses affecting some parameters when the solar cell was under backside illumination and emphasized the potential for improved energy harvest in bifacial solar cells without significant drawbacks.

Poly(acrylic acid)-modified SnO2/CdS double electron transport layers for efficient and stable Sb2(S,Se)3 solar cells

Antimony selenosulfide (Sb2(S,Se)3) solar cells hold significant promise for sustainable photovoltaic technology due to their adjustable band gap, high absorption coefficient and good stability. In terms of device operation, the transfer of electrons from the Sb2(S,Se)3 layer to the electron transport layer (ETL) plays a crucial role in improving the photovoltaic performance of solar cells. Until now, high-efficiency Sb2(S,Se)3 solar cells have typically employed cadmium sulfide (CdS) as the ETL. However, inadequate interface contact between the CdS and the Sb2(S,Se)3 layer often results in severe interface recombination, and the parasitic light absorption of CdS restricts the short-circuit current density (Jsc). Therefore, the development of high-quality CdS film along with reduction of cadmium element usage remains an import issue for the Sb2(S,Se)3 solar cells. Herein, the poly(acrylic acid)-modified tin oxide (PAA-SnO2)/CdS double ETLs are introduced to improve the quality of both the CdS film and Sb2(S,Se)3 film, while also strengthening the interface contact between CdS and Sb2(S,Se)3. The power conversion efficiency of the corresponding solar cells increases from 7.45% in the control device to 8.15% in the modified device. This work provides a simple PAA-modified SnO2-assisted CdS ETL strategy to improve the interface of CdS/Sb2(S,Se)3, thereby achieving efficient and stable Sb2(S,Se)3 solar cells.

A comprehensive analysis of structural, electronic, optical, mechanical, thermodynamic, and thermoelectric properties of direct band gap Sr3BF3 (B = As, Sb) photovoltaic compounds: DFT-GGA and mBJ approach

This study evaluates the physical properties of lead-free Sr3BF3 (B = As, Sb) photovoltaic compounds including structural, electronic, mechanical, optical, thermodynamic, and thermoelectric behavior using calculations based on DFT approach. Born stability criteria and formation enthalpy estimates show that the compounds under study are mechanically and thermodynamically stable. The initial lattice constants for Sr3AsF3 and Sr3SbF3 were determined to be 5.71 Å and 5.97 Å, respectively. While simulating the compounds under pressure, lattice constants, cell volumes, and bond lengths decrease. The band structure investigation shows that these compounds are semiconducting with an adjustable direct bandgap. The electronic band gap contracts by pressure, shifting the material from ultraviolet to the visible spectrum. This modification enhances electron transition from valence band maxima to conduction band minima, enhancing optical efficiency. The shift and rise in ductility and machinability index under pressure ensures good lubrication, low friction, and significant plastic deformation suitable for many industrial applications. Simultaneously, the static dielectric constant increases, increasing absorption and conductivity and red-shifting the optical spectrum, and reducing reflectivity in the visible spectrum. The thermodynamic behavior of the compounds was affected by both pressure and temperature variation. The thermoelectric figure of merit becomes closer to unity with a shorter band gap, indicating increased efficiency. Our findings suggest that Sr3BF3 (B = As, Sb) photovoltaic compounds could be used for the invention of next-generation solar cells and thermoelectric devices.

Four-Terminal Double-Junction Solar Cells Consisting of a Mesoscopic Wide-Bandgap Perovskite Solar Cell and an Inverted Narrow-Bandgap Perovskite Solar Cell with Spectral Splitting System

The spectral splitting system is one of the hybridization method to convine different solar cells to improve energy conversion efficiency by dividing sunlight into different spectral ranges. This technique is particularly valuable because different materials exhibit distinct spectral responses. By employing multiple types of solar cells optimized for different parts of the solar spectrum, overall panel efficiency can be increased compared to using a single type of solar cell. Implementing this technique requires careful design and engineering to ensure efficient spectral splitting and maximize electricity output from each type of solar cell. The organometal halide perovskite solar cell (PSC) exhibits a wide range of adjustable band gaps depending on its composition. To attain high efficiency in two-junction PSCs, combination of "mesoscopic" Pb-PSC with an "inverted" Sn-Pb mixed PSC is useful approach. In this study, a four-terminal spectral splitting double junction solar cell was fabricated by combining a mesoscopic-structure Pb-PSC and an inverted-structure Sn-Pb PSC, employing a dichroic mirror to split incident light into long and short wavelengths.In the experimental setup for the wide-bandgap top cell, initial steps involved the fabrication of compact and mesoscopic structure tin oxide layers on an FTO substrate. Subsequently, several wide-bandgap perovskite absorbers were spin-coated. Then, Spiro-OMeTAD was spin-coated onto the absorber layer, followed by thermal evaporation of gold. For the fabrication of the narrow-bandgap inverted PSC, a layer of PEDOT:PSS was spin-coated onto the FTO substrate. Then several narrow-bandgap perovskite absorbers were spin-coated. Finally, fullerene, bathocuproine, and silver were thermally evaporated onto the substrate. Finally, a four-terminal spectral splitting tandem solar cell was fabricated by combining the wide-bandgap mesoscopic structure top cell and the narrow-bandgap inverted structure bottom cell.J-V measurements conducted at several split wavelengths revealed a photovoltaic conversion efficiency (PCE) of over 20% for the top cell and about 5% for the bottom cell was obtained. However, the result showed that there is still room for improvement in bottom cell performance. As a result, the bandgap of narrow-bandgap perovskite was reduced by adjusting the ratio of tin and lead such as Cs0.025FA0.475MA0.5Sn0.6Pb0.4I3. This adjustment extended the optical absorption region of bottom cell to slightly longer wavelengths, as measured by EQE. Subsequently, the J-V measurements revealed a photovoltaic conversion efficiency of 20.1 % for the top cell and 5.36 % for the bottom cell at the 801 nm split. The total PCE of 25.5 % was obtained, surpassing previous results.

Triple-junction Dion–Jacobson perovskite tandem solar cells: advancing efficiency via interface optimization and broadened light absorption spectrum

Abstract Dion-Jacobson (DJ) perovskites have emerged as game-changers in the world of photovoltaics due to their unique combination of advantages like cost-effective fabrication, tailorable bandgap, and exceptional efficiency. Further, in this study, MXene contacts have been utilized with 2D-perovskites solar cells to leverage the advantages of both, leading to improved stability, superior charge transport, and adjustable energy bandgap without the occurrence of pinhole effects. To further tap into the immense potential of perovskites, this study explores the power of a triple-junction All DJ perovskite tandem solar cell (ADJT-PSC) architecture. This design captures a broader spectrum of sunlight, maximizing energy harvesting and unlocking new possibilities for photovoltaic devices. In this symphony of light and power, 1.5-pentamethylenediamine (PeDA) methylammonium lead iodide (PeDAMAPb2I7) (1.98 eV), PeDAMA5Pb6I19 (1.6 eV), CsLaTa2Se7 (1.1 eV) take as the absorber layers in the top, middle, and bottom subcells, respectively. Moreover, optimizing the thickness of each perovskite layer is crucial for maximizing efficiency. This study conducted a thorough analysis and identified the ideal 350 nm/550 nm/200 nm thicknesses for the top/middle/bottom layers, respectively. Furthermore, the study explored the art of doping variation in the electron and hole transport layers. By meticulously adjusting the doping levels, ADJT-PSC can achieve a maximum efficiency of 35%.

Porous Silicon-Supported Catalytic Materials for Energy Conversion and Storage.

Porous silicon (Si) has a tetrahedral structure similar to that of sp3-hybridized carbon atoms in a typical diamond structure, which affords it unique chemical and physical properties including an adjustable intrinsic bandgap, a high-speed carrier transfer efficiency. It has shown great potential in photocatalysis, rechargeable batteries, solar cells, detectors, and electrocatalysis. This review introduces various porous Si-supported electrocatalysts and analyzes the reasons why porous Si is used as a new carrier/active sites from the perspectives of its molecular structure, electronic properties, synthesis methods, etc. The electrochemical applications of porous Si-based electrocatalysts in energy conversion reactions such as hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, and total water decomposition together with lithium-ion battery and supercapacitor in energy storage are summarized. The challenges and future research directions for porous Si are also discussed. This review aims to deepen the understanding of porous Si and promote the development and applications of this new type of Si material.

Impact of Interfaces on the Performance of Covalent Organic Frameworks for Photocatalytic Hydrogen Production.

The rise in global temperatures and environmental contamination resulting from traditional fossil fuel usage has prompted a search for alternative energy sources. Utilizing solar energy to drive the direct splitting of water for hydrogen production has emerged as a promising solution to these challenges. Covalent organic frameworks (COFs) are ordered, crystalline materials made up of organic molecules linked by covalent bonds, featuring permanent porosity and a wide range of structural topologies. COFs serve as suitable platforms for solar-driven water splitting to produce hydrogen, as their building blocks can be tailored to possess adjustable band gaps, charge separation capabilities, porosity, wettability, and chemical stability. Here, the impact of the interface in the context of the photocatalytic reaction is focused and propose strategies to enhance the hydrogen production performance of COFs photocatalysis. In particular, how hybrid photocatalytic interfaces affect photocatalytic performance is focused.

Vacuum evaporation deposited RbxCs1-xPbBr3 thin films for spectrally tunable and stable all-inorganic blue light-emitting diodes

Perovskite light emitting diodes (PeLEDs) have emerged as a promising technology for new display applications due to their high color purity and precisely adjustable band gap. However, compared to green and red PeLEDs, blue PeLEDs suffer from lower luminous efficiency and stability. Traditionally, pure blue perovskite luminescence is achieved using mixed halogens, which often leads to phase separation issues. In this paper, we directly introduced RbBr and prepared RbxCs1-xPbBr3 (x = 0.5,0.6,0.7) thin films using thermal evaporation, achieving wavelength-tunable and stable blue light emission ranging from 477 nm to 489 nm.This is the first report of using thermal evaporation for the fabrication of RbxCs1-xPbBr3 films. PeLEDs based on these films exhibited stable electroluminescence under varying driving voltages. Operated continuously over 30 min at 6 V in ambient air with 36 % humidity, these devices showed superior spectral stability. Using pure bromine-based material RbxCs1-xPbBr3 (x = 0.5,0.6,0.7) in the light-emitting layer solves the problem of phase separation of mixed halogens and achieves blue-light emission. Additionally, the introduction of Rb+ distorts the crystal structure of perovskite. This distortion decreases the bond length of Pb-Br bonds, increases the bond energy, and raises the formation energy of halogen anion vacancies. As a result, the density of perovskite defect states decreases, and thus the stability is enhanced. This work represents a rare example of vacuum thermal-evaporation processed RbxCs1-xPbBr3 films and all-inorganic perovskite LEDs.

The Latest Applications of Carbon-Nitride-Based Materials for Combination Treatment of Cancer.

Carbon-nitride-based (CN-based) materials have shown great potential in combination therapy in recent years. Due to their outstanding biocompatibility, ease of modification, and adjustable band-gap position, CN-based materials can be applied as photosensitizers in photodynamic therapy (PDT) and light-driven water-splitting catalysts in gas therapy. After doping with other elements, the photocatalytic performance of CN-based materials will be enhanced, and more interesting functions will be obtained. In addition, the large specific surface area also promotes CN-based materials as drug carriers combined with other therapeutic modalities to achieve combination therapy. This Review analyzes and summarizes the latest research on CN-based materials in combined therapies, such as PDT with photothermal therapy (PTT), PDT with sonodynamic therapy (SDT), PDT with drug therapy, PDT with gene therapy, gas therapy with PDT, and bioimaging-guided combined therapy. In particular, the applications of CN-based materials in gas and gene combination therapy are summarized for the first time. Finally, the current challenges faced by CN-based materials in combination therapy are further discussed.

Advancing the Commercialization of Perovskite‐Based Radiation Detectors for High‐Resolution Imaging

AbstractRadiation detectors play an indispensable role in medical diagnostics, industrial non‐destructive inspection and national security. Recently, halide perovskites are considered as the new generation of radiation active materials due to excellent optoelectronic properties such as adjustable bandgap, high absorption coefficient, high carrier mobility and low cost. The radiation detectors based on perovskite show high sensitivity and low detection limit, contributing to excellent spatial resolution for imaging. However, the commercialization of perovskite radiation detectors for high quality imaging still faces many challenges, including ion migration in perovskite, fermi level pinning and electrochemical reaction at the interface of perovskite/electrode, and difficulties of integration with readout circuit. All the issues hinder the further improvement of device performance. This review summarizes the material forms and the optimized growth methods of perovskite for radiation imaging detectors. Further, this work focuses on challenges and improvements of the interface between perovskites and electrodes. Meanwhile, this work outlines the technical routes used to realize array detectors for radiation imaging. The comprehensive review would guide the commercialization of perovskite radiation detectors for high‐quality imaging.

Enhanced visible-light-driven photocatalytic degradation via in-situ AIS/ZIS high-low junctions

The I-III-VI QDs Ag-In-S (AIS) exhibits excellent properties in photocatalysis because of the adjustable band gap, wide light absorption range, and multiple active sites. Introducing homologous or heterogeneous ions not only derives the composition into quaternary/ quinary quantum dots but also generates new sulfide QDs to form composites, which is an effective strategy to promote photoactivity. In this work, we in-situ synthesized the AIS/ZIS (AgIn5S8/Zn4In2S7) composite photocatalyst by introducing Zn2+ and changing the reaction temperature. We found that the composite photocatalyst could efficiently photodegrade larger concentrations of RhB than that of the previous reports. The superior photocatalytic activity was due to the formation of the type I high-low junction, which could effectively separate carriers. The photoelectrons on the CB of AIS reacted with dissolved oxygen to produce strongly oxidative O2–, which degraded RhB into intermediates and eventually into CO2 and H2O. This work not only reports an excellent photocatalyst but also offers new ideas on the design and manufacture of highly efficient high-low junction photocatalysts.

Facile hydrothermal synthesis of melamine-based polymers for photocatalytic hydrogen evolution

Solar photocatalytic hydrogen evolution from water splitting has been recognized as a promising hydrogen production technology, the development of efficient, cheap, and practical new photocatalysts is the key to realizing this technology. Compared with semiconductor photocatalysts, polymeric photocatalysts have emerged due to their high structural diversity and adjustable band gaps. The synthesis process of the polymeric photocatalysts is generally complicated, and the reaction conditions are also harsh (such as oxygen free, using catalyst). In this work, melamine-based polymers (MP-1 and MP-2) were synthesized by a simple one-step hydrothermal method using melamine (MA) and p-phthalaldehyde (PPA) as precursors under air atmosphere without any additives. MP-1 and MP-2 display photocatalytic H2 evolution from water splitting in the presence of Pt as a co-catalyst and TEOA as a sacrificial hole scavenger. The effect of different structure of polymers on photocatalytic H2 evolution was discussed. The hydrogen evolution rate of MP-1 is 1784.2 umol·h−1·g−1, distinctly higher than that of MP-2 (1139.8 umol·h−1·g−1). The separation and migration of photoinduced carriers for MP-1 and MP-2 were investigated by electrochemical measurements and PL. It is thought that the imine (–C = N–) structure of MP-1 has a good conjugated system, which could generate more photoinduced electron-hole pairs under light excitation, and the charge migration is also more facile, compared with the aminal structure (–N–C–N–) of MP-2. This study is expected to contribute toward the development of “green hydrogen” using solar photocatalysis over synthetically facile polymeric photocatalysts.

Influence of growth temperature on the structural and optical characteristics of PbZnS thin films

Ternary thin films have garnered significant attention due to their adjustable band gap characteristics, making them suitable for many applications. In this research, we examined the structural and optical characteristics of PbZnS thin films fabricated onto glass substrates employing the spray pyrolysis techniuqe. The films were fabricated at different temperatures ranging from 300 to 400°C. X-ray diffraction (XRD) analysis indicated that all films displayed a cubic structure with a preferred orientation along the (200) plane. From the analysis of XRD peaks, it was observed that the crystal structure initially improved with increasing temperature but then began to degrade. These films demonstrated strong absorption in the range of 350–1600 nm. The optical bandgap (Eg) values, calculated based on the relationship between the absorption coefficient and photon energy, showed slight variations around 2 eV. Notably, the band gap decreased with growth temperatures up to 350°C, then increased at higher temperatures. These fluctuations are attributed to factors such as thermal expansion, strain, defects, surface/interface effects, and changes in doping or composition.

Emerging New-Generation Semiconductor Single Crystals of Metal Halide Perovskites for Radiation Detection

Radiation detection uses semiconductor materials to convert high-energy photons into charge (direct detection) or low-energy photons (indirect detection), and it has a wide range of applications in nuclear physics, medical imaging, astronomical detection, homeland security, and other fields. Metal halide perovskites have the advantages of high frequency number, high carrier mobility, high defect tolerance, low defect density, adjustable band gap, and fast light response, and they have wide application prospects in the field of radiation detection. However, the research is still in its infancy stage, and it is far from meeting the requirements of industrial application. This paper focuses on the advantages of metal halide perovskite single-crystal materials in both semiconductors-based direct conversion detection and scintillator-based indirect detection as well as the latest progress in this promising field. This paper not only introduces the latest application of lead halide perovskite monocrystalline materials in high-energy electromagnetic radiation detection (X-ray and γ-rays), but it also introduces the latest development of α-particle/β-particle/neutron detection. Finally, this paper points out the challenges and future prospects of metal halide perovskite single-crystal materials in radiation detection.

High-performance CIGS solar cells using a double active layers approach – SCAPS 1D optoelectronic modeling approach

One of the properties of the CIGS solar cell is that it can have an adjustable band gap energy. The band gap varies in the range from 1.01 to 1.7 eV as a function of materials content. Enhancing the bandgap profile of the active layer, which is where the majority of charge carrier photo-generation occurs, should significantly improve cell performance. Superimposing absorber layers with different electrical characteristics is one way of refining the bandgap profile and achieving these results. It is possible to analyze the optoelectronic output properties and simulate this active multilayer approach using a reference cell thanks to the SCAPS numerical modeling tool. Considering this, we have successfully simulated the following structure: CIGS2/CIGS1/SDL/ZnS/ZnO. The SDL which stands for Surface Defect Layer, has been considered for the property discontinuity interface, mainly characterized by the formation of defect states. That enabled to achieve realistic-like device with an improvement of power conversion efficiency (PCE) up to 11.98 %, i.e. 29.22 % and a fill factor (FF) of 82 % employing a total thickness of active layer of 800 nm. All simulations were performed considering experimental environment parameters, an external temperature of 300 K, light illumination of AM1.5G and defects states were assumed in both the bulk and at interfaces.

A Feasible Strategy for High-Performance Aqueous Zinc-Ion Batteries: Introducing Conducting Polymer.

Aqueous zinc ion batteries (AZIBs) offer great potential for large-scale energy storage because of their high safety, low cost and acceptable energy density. However, the cycle life of AZIBs is inevitably affected by parasitic reactions and dendritic growth caused by multiple factors such as electrode, electrolyte and separator, which pose significant obstacles to the practical application of AZIBs. To address these challenges, conducting polymer (CP) based materials have gained widespread attention in the realm of rechargeable batteries due to the adjustable band gap, controllable morphology, and excellent flexibility of CPs. In particular, CPs exhibit remarkable conductivity, low dimensionality, and doping characteristics, making them highly promising for integration into the AZIB system. In this review, the problems associated with the cathode, anode, electrolyte, and separator of AZIBs are discussed, and the application of CPs for their modification is summarized. The review provides a comprehensive analysis of the action mechanisms involved in the CP modification process and offers valuable insights for the design and development of CPs that can be effectively utilized in AZIBs. Additionally, the review presents a promising outlook of this research field, aiming to further advance the application of low-cost and high-performance CPs and their composites in AZIBs.

Zinc telluride material properties for solar cell application: Absorber layer

Over recent years, Zinc Telluride (ZnTe) has garnered significant interest from researches. This p-type semiconductors boasts a broad band gap, rendering it valuable in various optoelectronic uses like solar cells, LEDs, and laser displays. Given the growing interest in environmentally friendly energy alternatives, exploring the potential of nano-scale semiconducting materials for solar cells is particularly intriguing. ZnTe stands out due to its direct, wide, and adjustable optical band gap, along with its simple doping process, positioning it as a promising candidate for applications in photochemistry. This study aims to consolidate the research conducted by multiple investigators concerning the optical characteristics and electrical attributes of ZnTe thin films. The primary focus is on understanding how deposition methods and doping impacts these properties. The investigation reveals that the diverse doping techniques employed by different researchers have been extensively examined, demonstrating a positive influence of doping on these properties as well. Following the creation of solar cells based on ZnTe, they have emerged as viable and competitive substitutes for silicon solar cells, thanks to their economical nature and stable performance. As a result, there has been notable focus on advancing ZnTe thin film solar cell technology due to their promising capacity to serve as sustainable energy generators.

Prediction of a novel two-dimensional superatomic Cd6S2 monolayer for photocatalytic water splitting.

Two-dimensional transition metal dichalcogenides possess a significant specific surface area, adjustable bandgaps, and excellent optical absorption properties, rendering them highly conducive to photocatalytic applications. Herein, a MoS2-like 2D superatomic Cd6S2 monolayer is predicted, wherein the octahedral Cd6 superatom unit connects with S atoms via six vertices. Chemical bonding analysis reveals that the remarkable dynamic, thermal, and mechanical stability of the Cd6S2 monolayer results from the covalent Cd-S bonds and the 6-center 8-electron (6c-8e) delocalized bond within the Cd6 core, which ensures the chemical octet rule for both the S atom and the Cd6 superatom. Demonstrating notable optical absorption coefficients and a strain-tuned energy band structure, the Cd6S2 monolayer emerges as a viable candidate for catalyzing the solar-powered splitting of water. This work offers an alternative avenue to modify or improve the properties of 2D materials for photocatalytic applications through superatomic assembly.