Se Vacancies Research Articles

Origin of Oxidation Variations in Ambient-Stable β-InSe.

Understanding and controlling the oxidation of layered materials remain critical issues in the final stages of their practical application in devices. Layered materials achieve a band gap by removing inversion symmetry. However, the oxidation process becomes complex, and the oxidation of these materials is not yet fully understood. As a representative example, InSe has attracted considerable attention due to its high charge mobility and Si-like band gap. However, conflicting observations such as oxidation by Se and In have been reported, including contrasting assessments of the oxidation susceptibility. In this study, we report in situ spectroscopy results detailing the origins of various oxidation pathways. We observed that at low defect densities the reduced reaction barrier of InSe due to Se vacancies leads to oxygen adsorption, while as defects increase, the lower electronegativity of In rises as a new pathway for oxidation. At low defect density, the bulk layer was more energetically favored for oxygen adsorption, allowing oxygen to diffuse to a depth sufficient to form pseudoheterojunctions and making the surface layer seemingly resistant to oxidation. Our results provide an answer to why the resulting diversity of optical responses is expected to increase as well as strategies to achieve gas stability.

Hierarchical core-shell transitional metal chalcogenides Co9S8/ CoSe2@C nanocube embedded into porous carbon for tunable and efficient microwave absorption

In the domain of electromagnetic (EM) wave absorbing materials, the selection of suitable components and microstructures is an effective approach for designing the intense coupling of wave impedance and EM dissipation. In this study, we have successfully fabricated a double-carbon modified Co9S8/CoSe2 nanocube, where the core-shell Co9S8/CoSe2@C cube was anchored onto porous carbon (PC). The existence of three-dimensional (3D) porous carbon and the fabrication of Co9S8/CoSe2@C distributed on carbon nanosheets contribute to the improvement of conduction, magnetic losses, and the optimization of impedance matching. Substantial heterogeneous interfaces are generated between Co9S8, CoSe2, carbon shells, and PC, leading to extensive interfacial polarization and facilitating the transformation of EM energy into thermal energy. The abundant defects, S and Se vacancies in carbon component can act as polarization centers, inducing dipolar polarization and thus increasing the electromagnetic wave (EMW) loss. The Co9S8/CoSe2@C@PC exhibits the best microwave absorption properties, with a minimum reflection loss (RLmin) of −64.1 dB at 2.5 mm and an effective absorption bandwidth (EAB) of 6.3 GHz. The High-Frequency Structure Simulator results indicate the RCS values of the samples within the range of -90 °C < θ < 90 °C are lower than -20 dB m2, which can achieve almost full-angle coverage in the actual environment. This research offers inspiration and strategies for the design and synthesis of multi-component magneto-electric composites based on transitional metal chalcogenides.

Gradient Mo1−xWxSe2 monolayer Alloys: Synthesis and multifunctional applications

With the continuous and rapid development of electronic information technology, the demand for new materials with miniaturization, high integration, high performance, and multifunction is becoming increasingly urgent. However, it is difficult for existing photodetectors based on a single material to achieve multi-functionality while maintaining excellent performance, and the devices based on heterostructures are faced with complex preparation and compatibility problems. In this work, gradient Mo1−xWxSe2 monolayer alloys with high crystal quality have been synthesized by an evaporation-assisted chemical vapor deposition method. The composition of the synthesized Mo1−xWxSe2 monolayer alloys varies gradually with x ranging from 0 to 1. The Mo1−xWxSe2 based photodetector shows superior photoresponse performance in the visible wavelength with maximum responsivity of 26 A/W and external quantum efficiency up to 6320 % under 520 nm laser irradiation. Besides, the Mo1−xWxSe2 device is capable of high-resolution imaging, which can be used as image sensor. Moreover, nonvolatile memory function has also been realized in the device because the band gap of Mo1−xWxSe2 can be effectively adjusted by the gradient distribution of the component and the deep energy levels caused by Se vacancies can be modulated to shallow energy levels. A thrilling discovery is that the gradient Mo1−xWxSe2 alloy device can simulate the biological synapses successfully, including paired-pulse facilitation, short-term plasticity, long-term plasticity and learning process. The realization of high-performance photodetection, visualization, nonvolatile memory and synaptic simulation based on a single gradient crystal offers a new type of material to develop advanced optoelectronic devices with multiple functions.

Stepwise Optimization of Thermoelectric Performance in n‐Type SnS

AbstractTin sulfide (SnS) has been developed as an earth‐abundant and eco‐friendly compound that exhibits promising thermoelectric (TE) performance. While significant achievements are achieved in p‐type SnS, the development of its n‐type counterpart remains at a nascent stage, making it rather essential for developing n‐type SnS to ensure good compatibility in SnS‐based TE devices. In this study, Br is selected as the aliovalent dopant for realizing n‐type transport in SnS. Subsequently, isoelectronic Se alloying and vacancy compensation are utilized to further promote the TE performance for n‐type SnS. Se alloying can effectively narrow the bandgap of SnS for enhancing carrier concentration and diminishing thermal conductivity by strain and mass field fluctuations, while the excess Sn further compensates intrinsic Sn vacancies, thus optimizing carrier concentration and mobility simultaneously. These results are well verified by microstructure characterization and defect formation energy calculations. Consequently, the maximum ZT value of ≈0.7 and quality factor B of ≈1.02 at 823 K can be obtained after stepwise optimization, which is currently the highest value for n‐type SnS thermoelectrics. This study presents a significant progress for n‐type SnS and lays an important foundation for constructing all‐SnS‐based TE devices.

Low-temperature photoluminescence and Raman study of monolayer WSe2 for photocarrier dynamics and thermal conductivity

Low-temperature PL analysis reveals an intriguing temperature-dependent emission pattern in WSe2: excitonic dominance above the 150 K Debye temperature, a balance between excitonic and trionic emissions at 150 K, and trionic dominance below this threshold. At lower temperatures, both excitons and trions display linearly polarized emissions, with polarization increasing from 0% at 300 K to 23% (excitons) and 7% (trions) at 150 K, and 12% for trions at 90 K. Moreover, the synthesized monolayer of WSe2 exhibits high thermal conductivity (246 W m−1 K−1 for A1g and 185 W m−1 K−1 for E2g1 modes). This property is attributed to Se vacancies and defects at triangle edges, which redirect phonons, reducing scattering and enabling efficient heat transport along boundaries. The unveiling of these novel insights within the synthesized 2D WSe2 material holds significant promise for its potential applications in nano-optoelectronics. Its demonstrated efficiency in dissipating heat, coupled with improved thermal stability, suggests the possibility of employing it in future devices. This could facilitate compact designs and the miniaturization of advanced technological tools, showcasing the material's potential for practical implementation.

In situ seed layer bandgap engineering leading to the conduction band offset reversion and efficient Sb2Se3 solar cells with high open-circuit voltage

Sb2Se3 solar cells have achieved a power conversion efficiency (PCE) of over 10%. However, the serious open-circuit voltage deficit (VOC-deficit), induced by the hard-to-control crystal orientation and heterojunction interface reaction, limits the PCE of vapor transport deposition (VTD) processed Sb2Se3 solar cells. To overcome the VOC-deficit problem of VTD processed Sb2Se3 solar cells, herein, an in-situ bandgap regulation strategy is innovatively proposed to prepare a wide band gap Sb2(S,Se)3 seed layer (WBSL) at CdS/Sb2Se3 heterojunction interface to improve the PCE of Sb2Se3 solar cells. The analysis results show that the introduced Sb2(S,Se)3 seed layer can enhance the [001] orientation of Sb2Se3 thin films, broaden the band gap of heterojunction interface, and realize a “Spike-like” conduction band alignment with ΔEc = 0.11 eV. In addition, thanks to the suppressed CdS/Sb2Se3 interface reaction after WBSL application, the depletion region width of Sb2Se3 solar cells is widened, and the quality of CdS/Sb2Se3 interface and the carrier transporting performance of Sb2Se3 solar cells are significantly improved as well. Moreover, the harmful Se vacancy defects near the front interface of Sb2Se3 solar cells can be greatly diminished by WBSL. Finally, the PCE of Sb2Se3 solar cells is improved from 7.0% to 7.6%; meanwhile the VOC is increased to 466 mV which is the highest value for the VTD derived Sb2Se3 solar cells. This work will provide a valuable reference for the interface and orientation regulation of antimony-based chalcogenide solar cells.

Electronic properties of InSe/CNT heterojunctions with the modulation of electric field and vacancy defects

We investigate van der Waals (vdW) heterojunctions by combining InSe and zigzag carbon nanotubes (CNT(n,0)) by first-principle calculations. When n ranges from 5 to 7, The heterojunctions show n-type Schottky contact. However, for n of 8, 9, and 11, the heterojunctions still retain the characteristic of semiconductors with bandgaps. The metallized InSe/CNT(10,0) heterojunction has the most amount of charge transfer and the highest tunneling probability. Ohmic contact can be formed in InSe/CNT(n,0) (n = 5–7) heterojunctions under the external electric field. The charge transfer is enhanced and Schottky barrier heights are significantly reduced in heterojunctions with Se vacancy defect. In vacancy defect causes the disappearance of Schottky barrier because of metallization of InSe and more charge transfer than Se vacancy defect in InSe/CNT. Our findings provide a direction for the application of InSe/CNT in tunable nanoelectronic devices.

Defect design and vacancy engineering of NiCo2Se4 spinel composite for excellent electromagnetic wave absorption

Vacancy engineering presents an appealing method for modifying the electronic structure of spinel architectures. However, based on well-defined vacancy concentrations, how to design anionic vacancies to modulate electromagnetic parameters as well as electromagnetic wave absorption (EMA) properties is less studied. Here, NiCo2Se4 spinel structures were prepared using different selenization methods, and the Se vacancy defect concentration was controlled by changing the annealing temperature, thus regulating the EMA properties. Among them, the design of the hollow structure effectively enhanced the EMA performance. Moreover, the increase of Se vacancy concentration increases the conductivity loss while regulating the electronic structure, and also acts as an unsaturated site to induce the formation of dipoles to optimize the polarization loss. The effective absorption bandwidth (EAB) of NiCo2Se4-130 reaches 8.48 GHz at 2.4 mm at the highest Se vacancy concentration. This work establishes a direct relationship between vacancy concentration and the electromagnetic wave dissipation capability, offering valuable insights for the development of advanced EMA materials.

Synergistic Regulation of Polyselenide Dissolution and Na‐Ion Diffusion of Se‐Vacancy‐Rich Bismuth Selenide toward Ultrafast and Durable Sodium‐Ion Batteries

AbstractMetal selenides (MSes) have great potential as candidate anode materials in high‐specific‐energy sodium‐ion batteries (SIBs) but are plagued by rapid capacity degradation and slow kinetics. Here, it is reveal that the Bi2Se3 anode discharge process involves multiple‐types of sodium polyselenides (Na‐pSex) which suffer from terrible dissolution and shuttling properties. Based on these observations, a nanoflower‐like composite of dual carbon‐confined Bi2Se3−x crystallites is designed via facile defect chemistry. The robust dual N‐doped carbon layer suppresses the precipitation and aggregation of Bi2Se3, significantly alleviating the dissolution and shuttle effect of Na‐pSex. Theoretical calculations indicate that the pyridine/pyrrole nitrogen sites exhibit strong van der Waals resistance and chemisorption properties against Na2Se4 and Na2Se2. Furthermore, the abundant Se vacancies improve the inherent conductivity of Bi2Se3, reduce the diffusion barrier of Na+, and accelerate the reaction kinetics. Consequently, the resulting Bi2Se3−x@DNC electrode exhibits extraordinary durability (over 2000 cycles at 10.0 A g−1) and high‐rate capability (354.4 mAh g−1 at 75.0 A g−1), propelling the battery performance to new heights. Encouragingly, the assembled hybrid capacitor displays competitive rate performance and an ultra‐long lifespan exceeding 40 000 cycles, making the Bi2Se3−x@DNC electrode a promising candidate for SIBs.

Vacancy-driven resistive switching behavior based on wafer-scale MoSe2 artificial synapses

Recently, researches have revealed that synaptic transistors based on two-dimensional materials (2DMs) have substantial advantages and potential for modeling neural synapses. However, the mechanism of artificial synaptic device with 2DMs as conducting channels remains to be further clarified. Here, high-quality wafer-scale MoSe2 nanosheets were achieved by ALD-CVD process, where further 23 × 23 × 4 synaptic arrays were fabricated in situ. Notably, the outstanding MoSe2 synaptic device exhibits an on/off ratio of 3.6 × 107 with hysteresis ratio of 6.8k and simulates crucial biological synaptic behaviors such as paired pulse facilitation and excitatory postsynaptic currents. The mechanism of Se vacancy induction and horizontal diffusion driven is revealed based on high-resolution transmission electron microscopy characterization with first-principles calculations, which suggests a possible mechanistic explanation for the resistive switching behavior of 2DMs transistors. Artificial synaptic devices with 2DMs based on the working mechanism of vacancy diffusion are capable of satisfying the needs of complex neural network applications.

Enhancing electrocatalytic nitrate/nitric oxide reduction to NH3 on two-dimensional p-block InSe monolayer via defect engineering

Electrochemical nitrate/nitric oxide (NO3−/NO) reduction to ammonia (NH3) is an environmentally friendly and sustainable strategy that mitigates pollutants while synthesizing value-added products NH3. Despite the prevalence of transition metal-based catalysts, the exploration of inexpensive two-dimensional (2D) p-block materials is needed in NH3 synthesis. Based on density functional theory calculations, we proposed an InSe monolayer with single Se vacancy as an outstanding catalyst for NO3RR and NORR. The catalyst exhibits exceptional catalytic performance, characterized by a low limiting potential comparable to that of most transition metal-based catalysts, and efficaciously suppresses the formation of competitive by-products. Successful adsorption and activation of NO3− and NO molecules are achieved, attributed to the charge rearrangement around the vacancy. The electronic structure analysis reveals that the enhancement of activity stems from the upward shift of the p-band center of unsaturated indium atoms. This work heralds a novel avenue for designing pure 2D p-block NH3 synthesis catalysts and sheds light on a deeper understanding of the catalytic mechanism at the electronic level.

Regulating the microstructure and catalytic activity of metal selenides via calcination strategy for lithium-sulfur battery

Metal selenides obtain a series of advantages such as high electronic conductivity, excellent catalytic activity and facile fabrication approach, which are considered as promising catalysts in lithium sulfur (Li-S) battery. Traditional research based on metal selenides focuses on designing novel/complex microstructures or composites, however, the catalytic ability can be greatly affected by internal properties such as defect or vacancy. In this work, hollow nickel-cobalt layered double hydroxide (NiCo-LDH) is first fabricated and applied as a precursor to fabricate NiCoSe, and Se vacancy accompanied with crystal phase, microstructure and catalytic activity can be regulated by simply adjusting selenization atmosphere and temperature. Involving the application of NiCoSe in Li-S battery, the optimum fabrication parameter is perform the selenization at 600 °C under argon/5 % hydrogen, and the battery can exhibit a high discharge specific capacity of 1042.8 mAh g−1, excellent cycling performance of 500 cycles with a decay rate of 0.083 % at 1 C. This work highlights the importance of calcination process and also provides reference for further modifying the microstructure and performance of metal selenides in Li-S battery.

Se Vacancy Activated Bi2Se3 Nanodots Encapsulated in Porous Carbon Nanofibers for Aqueous Zinc and Ammonium Ion Batteries

AbstractBismuth‐based materials show great potential in aqueous batteries. But it is difficult to design a bifunctional bismuth‐based material for zinc and ammonium ion batteries (ZIBs and AIBs). Herein, a electrospinning method followed by a selenization strategy is used to design Bi2Se3 nanodots embedded in porous carbon nanofibers. Experimental studies coupled with theoretical calculations prove that the designs of nanodot and Se vacancy improve the transfer and storage of Zn2+ and NH4+. Bi2Se3 nanodots are restricted to porous carbon nanofibers during cyclic test. An insertion‐type mechanism is revealed by ex situ characterizations. As a result, this well‐designed electrode (6 mg cm−2) offers high reversible capacities of 270 mA h g−1 in ZIBs and 192 mA h g−1 in AIBs at 0.05 A g−1 and long‐term cycle life (60% capacity retention at 10 A g−1 after 20 K cycles for ZIBs, 78% capacity retention at 2 A g−1 after 9 K cycles for AIBs). Remarkably, it still displays satisfactory performances even at an ultrahigh mass loading of 18 mg cm−2. Furthermore, Zn2+ and NH4+ full cells offer high reversible capacities of 120 and 90 mA h g−1 at 0.05 A g−1 respectively. This work provides a reference for designing a bifunctional electrode.

Se-vacancy porous ultrathin ZnSe nanosheet/carbon composite for sodium storage via electron beam irradiation strategy

Zinc selenide (ZnSe) is a next-generation anode material due to its high sodium storage capacity. However, the poor conductivity and volume expansion lead to its capacity attenuation and short cycle life. Herein, Se-vacancy porous ultrathin ZnSe nanosheet/carbon composite (ZnSe@NC/N-GQD) is reported as a high-performance anode material for sodium-ion batteries. Organic-inorganic hybrid ZnSe(en)0.5 ultrathin nanosheets with abundant Se vacancies are rapidly prepared by electron beam irradiation for the first time. Using it as a precursor, Se-vacancy carbon-coated porous ultrathin ZnSe nanosheets loaded with nitrogen-doped graphene quantum dots (N-GQDs) are synthesized via carbonization and electrodeposition process. Through the design of ZnSe@NC/N-GQD, the sodium storage performance can be effectively improved by implementing nanostructure engineering (porous ultrathin nanosheet) via organic–inorganic hybrid, defect engineering (Se vacancy) via electron beam irradiation, and carbon composite (amorphous carbon and N-GQD). Consequently, ZnSe@NC/N-GQD delivers a high capacity of 483 mA h g−1 after 200 cycles at 0.5 A g−1, shows an outstanding rate capability of 381 mA h g−1 at 10.0 A g−1, and exhibits an excellent cycling stability of 86 % retention after 2800 cycles at 5.0 A g−1. This work develops a new method to rapidly prepare organic–inorganic nanohybrids, and proposes an innovative design of high-performance ZnSe-based anodes.

Se vacancies and interface engineering modulated bifunctionality prussian blue analogue derivatives for overall water splitting

It is a challenging task to design and synthesize stable, and high-performance non-precious metals bifunctional catalysts for water-splitting. Herein, the coupling between Se vacancy and interface engineering is highlighted to synthesize a unique CoFeSe hollow nanocubes structure on MXene-modified nickel foam (NF) by in-situ phase transition from bifunctionality prussian blue analogue (PBA) derivatives (VSe-CoFeSe@MXene/NF). DFT theory reveals that the Se vacancy and interface engineering modulate the surface electronic structure and optimize the surface adsorption energy of the intermediates. Experimental data also confirm that the as-prepared CoFeSe@MF catalyst exhibits advanced electrocatalytic properties, 283 mV (OER) and 67 mV (HER) are required to drive the current density of 10 mA cm−2. Notably, it is assembled into a two-electrode system for integral water decomposition, which only requires a low cell potential of 1.57 V at current of 10 mA cm−2, together with excellent durability for 48 h. The strategy is expected to provide a new direction for the design and construction of highly efficient collaborative integrated water decomposition electrocatalysts.

(Invited) Enhanced Catalysis of Surface-Activated Metallic WSe2 Nanosheets By Single-Atom Pt for High-Performance Li-O2 Battery

Layered materials, such as TMDCs, exhibit various electronic structures attributed to their polymorphism and can be further modificated at the atomic level through chemical treatments. TMDCs in the metallic phase (1T or 1T’ phase) have gained attention as efficient electrocatalystic materials, due to their exceptional transport properties compared to TMDCs in the semiconducting phase (2H phase). TMDCs with the metallic phase have been prepared by atomic-scale post-treatments, such as an intercalation and single-atom doping. However, the precise role of these post-treatments in the catalytic performance of TMDCs is still ambiguous, as it is uncertain whether the enhanced properties arise from charge transfer kinetics in metallic phase or electrochemical properties induced by the post-treatment.Herein, we present a straightforward approach fabrication for fabricating metallic WSe2 nanosheets, which serve as an excellent support for single-atom Pt doping. The incorporation of single-atom Pt into WSe2 nanosheets was achieved using a simple solution method at room temperature. Extensive measurements were conducted, including XAS, XPS, and XPDF to investigate the local coordination structure of Pt-WSe2. These measurements confirmed the presentce of single-atom Pt doping within WSe2 layers. The introduction of single-atom Pt significantly enhanced the kinetics of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), leading to improved performance of Li-O2 batteries. Experimental measurements and DFT calculations provided evidence that the enhanced catalytic abilities of Pt-WSe2 originated from the improved interaction between oxygen and the Se vacancy on basal planes of WSe2. Consequently, the Li-O2 battery incorporating the Pt-WSe2 catalyst exhibited a stable discharge and charge cycle for up to 350 cycles, demonstrating its superior durability.

(Invited) Bulk Traps in Layered 2D Gate Dielectrics

Ultra-thin ferromagnets, when coupled with magnetoelectric or multiferroic materials, could potentially enable highly energy-efficient electric field control of the magnet for use in nanoelectronic memories. Substitutional doping of magnetic impurities in monolayer transition metal dichalcogenides (TMDs) may be a promising way to create 2D ferromagnets but, according to theoretical calculations, require high doping levels (10-20 %) to achieve above room temperature (RT) Curie temperature. Room-temperature ferromagnetism has been reported for very low doping levels (0.1-1%), in conflict with the theoretical calculations, and always in the presence of high concentrations of defects, making it unclear if the dopants alone are responsible for this ferromagnetism. In this work, we use a combination of molecular beam epitaxy (MBE), plan-view TEM, XRD, XPS, Raman, and magnetometry to study iron and vanadium doping in monolayer WSe2. We show that optimally grown monolayers with up to 35% doping and low defect density show no ferromagnetism. Interestingly, ferromagnetism is observed when these monolayers contain a significant amount of selenium vacancies (Sevac), intentionally created via a post-growth heat treatment process, and magnetism is seen to scale with heating time/vacancy concentration. Moreover, even undoped WSe2 shows similar ferromagnetism for Sevac > 1014 cm-2. This ferromagnetism can later be quenched by filling these vacancies via Se annealing. For films with low Se vacancy concentration, TEM analysis reveals significant clustering of the V and Fe dopants which likely suppresses the ferromagnetism predicted by theory - a problem that has previously plagued III-V based dilute magnetic semiconductors as well. We go so far as to claim that all of the above room-temperature ferromagnetism reports in the literature thus far are due to Se vacancies and not magnetic doping.

Effects of vacancy defects and atomic doping on the electronic and magnetic properties of puckered penta-like PdPSe monolayer: an Ab initio study

The experimental knowledge of two-dimensional penta-like PdPSe monolayer is largely based on a recent publication (Liet al2021Adv. Mater. 2102541). Therefore, the aim of our research is consequently to explore the effect of vacancy defects and substitutional doping on the electronic properties of the novel penta-PdPSe monolayer by using first-principles calculations. Penta-like PdPSe is a semiconductor with an indirect bandgap of 1.40 eV. We show that Pd and Se vacancy defected structures are semiconductors with band gaps of 1.10 eV and 0.95 eV respectively. While P single vacancy and double vacancy defected structures are metals. The doping with Ag (at Pd site) and Si (at P site) convert the PdPSe to nonmagnetic metallic monolayer while the doping with Rh (at Pd site), Se (at P site) and As (at site Se) convert it to diluted magnetic semiconductors with the magnetic moment of 1µB. The doping with Pt (at the Pd site), As (at the P site), S and Te (at Se site) are indirect semiconductors with a bandgap of ∼1.2 eV. We undertook this theoretical study to inspire many experimentalists to focus on penta-like PdPSe monolayer growth incorporating different impurities and by defect engineering to tune the novel two dimensional materials (PdPSe) properties for the advanced nanoelectronic application.

Wafer‐Scale Fabrication of Broadband Sb2Se3 Photodetectors and their Multifunctional Optoelectronic Applications

AbstractLow‐dimensional van der Waals materials (vdWMs) have attracted worldwide interest on account of numerous advantages including self‐passivated surface, high carrier mobility, excellent flexibility, etc. Among multiple vdWMs, Sb2Se3 stands out due to its high light absorption coefficient, environmentally friendly components, excellent stability, and abundant reserve. However, limited effective wavelength range and unscalable preparation have been obstinate issues standing in the way of further development. Herein, pulsed‐laser deposition (PLD) has been developed for synthesizing Sb2Se3 nanofilms, and wafer‐scale deposition has been realized. The PLD‐derived Sb2Se3 photodetector demonstrates broadband photoresponse across UV to NIR. First‐principles calculations have determined that this is because the formation of Se vacancies can result in a reduction of the bandgap. Upon 635 nm illumination, an optimal responsivity of 2.68 A W−1 has been achieved, corresponding to an external quantum efficiency of 524% and a specific detectivity of 1.34 × 1012 Jones. Furthermore, the device manifests a short response/recovery time of ≈2/1 ms. Proof‐of‐concept broadband imaging as well as fitness monitoring (respiratory rate &amp; heart rate) have been realized. Profited from the scalable preparation, an array of Sb2Se3 photodetectors have been produced, exhibiting qualified device‐to‐device variation. On the whole, this study has depicted an attractive landscape for next‐generation integrated optoelectronics.

Defect-mediated Fermi level modulation boosting photo-activity of spatially-ordered S-scheme heterojunction

Spatially-ordered S-scheme photocatalysts are intriguing due to their enhanced light harvesting, spatially isolated redox sites, and strong redox abilities. Nonetheless, heightening the performance of S-scheme photocatalysts via controllable defect engineering is still challenging to now. In this work, multi-armed MoSe2/CdS S-scheme heterojunction with intimate Mo-S bond coupling and adjustable Se vacancies (VSe) and Mo5+ concentrations was constructed, which consisted of few- or even single-layered MoSe2 growing on the {11–20} facets of wurtzite CdS arms. The S-scheme charge transmission mechanism of MoSe2/CdS heterojunction was validated by density functional theory calculation combined with in situ photo-irradiated X-ray photoelectron spectroscopy, surface photovoltage, and radical measurements. Moreover, the Fermi level gap between CdS and MoSe2 was enlarged by regulating the contents of donor (VSe) and acceptor (Mo5+) impurities with synthesis temperature, which strengthens the built-in electric field and carriers transfer driving force of MoSe2/CdS composites, contributing to an outstanding H2 evolution activity of 52.62 mmol·g−1·h−1 (corresponding to an apparent quantum efficiency of 34.8 % at 400 nm) under visible-light irradiation (λ > 400 nm), 25.8 times that of Pt-loaded CdS counterpart and a substantial amount of reported CdS-containing photocatalysts. Our study results are anticipated to facilitate the rational design of advanced semiconductor nanostructures for efficient solar conversion and utilization.