Diameter-controlled and surface-modified Sb₂Se₃ nanowires and their photodetector performance

Recent Advances in Antimony Selenide Photodetectors

Photodetectors (PDs) rapidly capture optical signals and convert them into electrical signals, making them indispensable in a variety of applications including imaging, optical communication, remote sensing, and biological detection. Recently, antimony selenide (Sb2Se3) has achieved remarkable progress due to its earth-abundant, low toxicity, low price, suitable bandgap width, high absorption coefficient, and unique structural characteristics. Sb2Se3 has been extensively studied in solar cells, but there's a lack of timely updates in the field of PDs. A literature review based on Sb2Se3 PDs is urgently warranted. This review aims to provide a concise understanding of the latest progress in Sb2Se3 PDs, with a focus on the basic characteristics and the performance optimization for Sb2Se3 photoconductive-type and photodiode-type detectors, including nanostructure regulation, process optimization, and stability improvement of flexible devices. Furthermore, the application progresses of Sb2Se3 PDs in heart rate monitoring, and monolithic-integrated matrix images are introduced. Finally, this review presents various strategies with potential and feasibility to address challenges for the rapid development and commercial application of Sb2Se3 PDs.

Charge Puddles Driven Complex Crossover of Magnetoresistance in Non-Topological Sulfur Doped Antimony Selenide Nanowires

A race to achieve a crossover from positive to negative magnetoresistance is intense in the field of nanostructured materials to reduce the size of memory devices. Here, the unusual complex magnetoresistance in nonmagnetic sulfur-doped Sb2Se3 nanowires is demonstrated. Intentionally, sulfur is doped in such a way to nearly achieve the charge neutrality point that is evident from switching of carrier type from p-type to n-type at 13 K as inferred from the low-temperature thermoelectric power measurements. A change from 3D variable range hopping (VRH) to power law transport with α = 0.18  in resistivity measurement signifies a Luttinger liquid transport with weak links through the nanowires. Interestingly, high magnetic field induced negative magnetoresistance (NMR) occurring in hole dominated temperature regimes can only be explained by invoking the concept of charge puddles. Spot energy dispersive spectroscopy (EDS), magnetic force microscopy (MFM) measurements, Tmott and Regel plot indicate an enhanced disorder in these sulfurized nanowires that are found to be the precursor for the formation of these charge puddles. Tunability of conducting states in these nanowires is investigated in the light of interplay of carrier type, magnetic field, temperature, and intricate intra-inter wire transport that makes this nanowires potential for large scale spintronic devices.

Ultrafast Electron and Hole Transfer and Efficient Charge Separation in a Sb2Se3/CdS Thin Film p-n Heterojunction

Harvesting solar energy for different applications requires the continuous development of new semiconducting materials to exploit a broad part of the solar spectrum. In this direction, antimony selenide (Sb2Se3) has attracted a tremendous amount of attention over the past few years as a light-harvesting material for photovoltaic device applications owing to its phase stability, high absorption coefficient, earth abundance, and low toxicity. Here, we have fabricated a high-quality heterojunction of a p-type Sb2Se3 film and an n-type CdS film using the thermal evaporation technique. The photocurrent of the heterosystem was significantly higher than that of the pristine materials. This optoelectronic response was investigated using femtosecond transient absorption (TA) spectroscopy. TA study reveals the existence of an instantaneous electron transfer from Sb2Se3 to CdS, accompanied by a substantial charge separation at the heterojunction. Our study deals with the investigation of a well-designed p-n device, paving the way for the fabrication of highly efficient photovoltaic devices.

Embedded Integration of Sb2Se3 Film by Low-Temperature Plasma-Assisted Chemical Vapor Reaction with Polycrystalline Si Transistor for High-Performance Flexible Visible-to-Near-Infrared Photodetector

Flexible optoelectronics have garnered considerable interest for applications such as optical communication, motion capture, biosignal detection, and night vision. Transition-metal dichalcogenides are widely used as flexible photodetectors owing to their outstanding electrical and optical properties and high flexibility. Herein, a two-dimensional (2D) Sb₂Se₃ film-based one transistor-one resistor (1T1R) flexible photodetector with high photosensing current and detection ranges from visible to near-infrared was developed. The flexible 1T1R was fabricated using an efficient field-effect transistor platform with the 2D Sb₂Se₃ film directly deposited on the sensing region using a low-temperature plasma-assisted chemical vapor reaction. The photodetector could achieve a maximum I_photo/I_dark of 15,000 under white light with a power density of 26 mW/cm², in which the photodetector showed quick rising and falling response times of 0.16 and 0.28 s, respectively. The 2D Sb₂Se₃ film exhibits broadband absorption in the visible and IR regions, yielding an excellent photoresponse under laser illumination with different wavelengths. To investigate the flexibility and stability of the 1T1R photodetector, the photoresponses were measured under different bending cycles and curvatures, which maintained its functions and exhibited high stability under convex and concave bending at a curvature radius of 20 mm.

Orientation dependence of electronic properties of antimony selenide nanowires

We present a comprehensive DFT study of size-dependent atomic and electronic properties of antimony selenide (Sb 2 Se 3) nanowires in three main crystallographic directions. Our calculations show a significant enhancement in the band gap of wires oriented in [100] and [010] directions due to confinement effects, however the band gap of [001] oriented wires is reduced with respect to bulk. We attribute this anomaly in band gap reduction to the surface reconstructions in these nanostructures. These surface reconstructions are similar to the polyhedral distortions observed in bulk Sb 2 Se 3 under high pressure leading to the insulator-metal transition related to the topological insulating states and then at lower temperature (8K) to superconductivity.

Sb2S3/Sb2Se3 heterojunction for high-performance photodetection and hydrogen production

Photoelectrochemical (PEC)-type devices provide promising ways for harvesting solar energy and converting it to electric and chemical energy with a low-cost and simple manufacturing process. However, the high light absorption, fast carrier separation, and low carrier recombination are still great challenges in reaching high performance for PEC devices. As emergent two-dimensional (2D) materials, Sb₂Se₃ and Sb₂S₃ exhibit desirable photoelectric properties due to the narrow bandgap, large optical absorption, and high carrier mobility. Herein, Sb₂S₃/Sb₂Se₃ heterojunction is synthesized by a two-step physical vapor deposition method. The type-II Sb₂S₃/Sb₂Se₃ heterojunction displays excellentphotoelectric properties such as a high photocurrent density (I_ph ∼ 162 µA cm^-2), a high photoresponsivity (R_ph ∼ 3700 µA W^-1), and a fast time response speed (rising time ∼ 2 ms and falling time ∼ 4.5 ms) even in harsh environment (H₂SO₄ electrolyte). Especially, the Sb₂S₃/Sb₂Se₃ shows an excellent self-powered photoresponse (I_ph ∼ 40 µA cm^-2, R_ph ∼ 850 µA W^-1). This increment is attributed to the improvement in light absorption, charge separation, and charge transfer efficiency. Taking these advantages, the Sb₂S₃/Sb₂Se₃ heterojunction also exhibits higher PEC water splitting synergically, which is approximately 3 times larger than that of Sb₂Se₃ and Sb₂S₃. These results pave the way for high-performance PEC devices by integrating 2D narrow bandgap semiconductors.

Thermoelectric properties of antimony selenide hexagonal nanotubes

Antimony selenide (Sb₂Se₃) is a material widely used in photodetectors and relatively new as a possible material for thermoelectric applications. Taking advantage of the new properties after nanoscale fabrication, this material shows great potential for the development of efficient low temperature thermoelectric devices. Here we study the synthesis, the crystal properties and the thermal and thermoelectric transport response of Sb₂Se₃ hexagonal nanotubes (HNT) in the temperature range between 120 and 370 K. HNT have a moderate electrical conductivity ∼10² S m^-1 while maintaining a reasonable Seebeck coefficient ∼430 μV K^-1 at 370 K. The electrical conductivity in Sb₂Se₃ HNT is about 5 orders of magnitude larger and its thermal conductivity one half of what is found in bulk. Moreover, the calculated figure of merit (ZT) at room temperature is the largest value reported in antimony selenide 1D structures.

Silicon nanowire core-shell PN junction phototransistors by self-assembled monolayer doping

Nanoscale photoconductors often have extremely high gain in quantum efficiency but suffer from the difficulty to design the density of surface states that cause the high photogain. In this Letter, we created high-gain photoconductors by forming a core-shell PN junction in silicon nanowires via self-assembled molecular monolayer doping. The highly doped n-type shell deactivates all the surface states by filling with electrons so that the n-type shell as a well, instead of the surface states, captures and emits photogenerated minority electrons under ON/OFF light illumination. The corresponding excess majority holes are accumulated in the nanowire channel and thus modulate the channel width, resulting in the experimentally observed high photogain (∼10⁸). The photoresponses of these phototransistors were systematically investigated as a function of the nanowire width and light illumination intensity. The results show that the nanowire channel is pinched off for the nanowires narrower than 73 nm due to the core-shell PN junction. We further derived analytical equations based on the PN junction device principle, finding the explicit gain equation that governs the photogain as a function of light intensity and other physical parameters of the nanowires. The explicit gain equations can fit well with the experimental data and allow us to design the core-shell nanowire phototransitors with desired performance.

Chemical Vapor Deposition Growth of High Crystallinity Sb2 Se3 Nanowire with Strong Anisotropy for Near-Infrared Photodetectors

Low-dimensional semiconductors have attracted considerable attention due to their unique structures and remarkable properties, which makes them promising materials for a wide range of applications related to electronics and optoelectronics. Herein, the preparation of 1D Sb₂ Se₃ nanowires (NWs) with high crystal quality via chemical vapor deposition growth is reported. The obtained Sb₂ Se₃ NWs have triangular prism morphology with aspect ratio range from 2 to 200, and three primary lattice orientations can be achieved on the sixfold symmetry mica substrate. Angle-resolved polarized Raman spectroscopy measurement reveals strong anisotropic properties of the Sb₂ Se₃ NWs, which is also developed to identify its crystal orientation. Furthermore, photodetectors based on Sb₂ Se₃ NW exhibit a wide spectral photoresponse range from visible to NIR (400-900 nm). Owing to the high crystallinity of Sb₂ Se₃ NW, the photodetector acquires a photocurrent on/off ratio of about 405, a responsivity of 5100 mA W^-1 , and fast rise and fall times of about 32 and 5 ms, respectively. Additionally, owing to the anisotropic structure of Sb₂ Se₃ NW, the device exhibits polarization-dependent photoresponse. The high crystallinity and superior anisotropy of Sb₂ Se₃ NW, combined with controllable preparation endows it with great potential for constructing multifunctional optoelectronic devices.

Dynamics of Charge Carriers in Silicon Nanowire Photoconductors Revealed by Photo Hall Effect Measurements

Photoconductors have extraordinarily high gain in quantum efficiency, but the origin of the gain has remained in dispute for decades. In this work, we employ photo Hall effect to reveal the gain mechanisms by probing the dynamics of photogenerated charge carriers in silicon nanowire photoconductors. The results reveal that a large number of photogenerated minority electrons are localized in the surface depletion region and surface trap states. The same number of excess hole counterparts is left in the nanowire conduction channel, resulting in the fact that excess holes outnumber the excess electrons in the nanowire conduction channel by orders of magnitude. The accumulation of the excess holes broadens the conduction channel by narrowing down the depletion region, which leads to the experimentally observed high photo gain.

Ionic liquid bifunctionally modulated aggregation-coalescence mechanism to synthesize SnSe single-crystal nanorod/nanoparticle core shell nanostructures and single-crystal nanorods for optoelectronics

Ionic liquid-bifunctional modulated synthesis of SnSe nanorafts and nanorods for optoelectronics.

Colloidal synthesis and characterization of single-crystalline Sb2Se3 nanowires

Single-crystalline Sb₂Se₃ nanowires have been synthesized by a hot-injection phosphine-free colloidal method and show excellent photoelectrochemical properties.

Thermal and Thermoelectric Transport in Highly Resistive Single Sb2Se3 Nanowires and Nanowire Bundles

In this study, we measured the thermal conductivity and Seebeck coefficient of single Sb₂Se₃ nanowires and nanowire bundles with a high resistivity (σ ~ 4.37 × 10⁻⁴ S/m). Microdevices consisting of two adjacent suspended silicon nitride membranes were fabricated to measure the thermal transport properties of the nanowires in vacuum. Single Sb₂Se₃ nanowires with different diameters and nanowire bundles were carefully placed on the device to bridge the two membranes. The relationship of temperature difference on each heating/sensing suspension membranes with joule heating was accurately determined. A single Sb₂Se₃ nanowire with a diameter of ~ 680 nm was found to have a thermal conductivity (k_NW) of 0.037 ± 0.002 W/m·K. The thermal conductivity of the nanowires is more than an order of magnitude lower than that of bulk materials (k ~ 0.36–1.9 W/m·K) and highly conductive (σ ~ 3 × 10⁴ S/m) Sb₂Se₃ single nanowires (k ~ 1 W/m·K). The measured Seebeck coefficient with a positive value of ~ 661 μV/K is comparable to that of highly conductive Sb₂Se₃ single nanowires (~ 750 μV/K). The thermal transport between wires with different diameters and nanowire bundles was compared and discussed.

An Antimony Selenide Molecular Ink for Flexible Broadband Photodetectors

The need for low-cost high-performance broadband photon detection with sensitivity in the near infrared (NIR) has driven interest in new materials that combine high absorption with traditional electronic infrastructure (CMOS) compatibility. Here, we demonstrate a facile, low-cost and scalable, catalyst-free one-step solution-processed approach to grow one-dimensional Sb₂Se₃ nanostructures directly on flexible substrates for high-performance NIR photodetectors. Structural characterization and compositional analyses reveal high-quality single-crystalline material with orthorhombic crystal structure and a near-stoichiometric Sb/Se atomic ratio. We measure a direct band gap of 1.12 eV, which is consistent with predictions from theoretical simulations, indicating strong NIR potential. The fabricated metal-semiconductor-metal photodetectors exhibit fast response (on the order of milliseconds) and high performance (responsivity ~ 0.27 A/W) as well as excellent mechanical flexibility and durability. The results demonstrate the potential of molecular-ink-based Sb₂Se₃ nanostructures for flexible electronic and broadband optoelectronic device applications.

Facile synthesis of hybrid nanorods with the Sb2Se3/AgSbSe2 heterojunction structure for high performance photodetectors

An effective colloidal process involving the hot-injection method is developed to synthesize uniform single-crystalline Sb2Se3 nanorods in high yields. The photoconductive characteristics of the as-synthesized Sb2Se3 nanorods are investigated by developing a film-based photodetector and this device displays a remarkable response to visible light with an "ON/OFF" ratio as high as 50 (with an incident light density of 12.05 mW cm(-2)), short response/recovery times and long-term durability. To overcome the challenge of the intrinsic low electrical conductivity of Sb2Se3, hybrid nanorods with the Sb2Se3/AgSbSe2 heterojunction structure having a type-II band alignment are firstly prepared. The electric current of the photodetector based on the Sb2Se3/AgSbSe2 hybrid nanorod film has been significantly increased both in the dark and under light illumination. The responsivity of the photodetector based on the Sb2Se3/AgSbSe2 hybrid nanorod film is about 4.2 times as much as that of the photodetector based on the Sb2Se3 nanorod film. This improvement can be considered as an important step to promote Sb2Se3 based semiconductors for applications in high performance photodetectors.

High-performance flexible photodetectors based on single-crystalline Sb2Se3 nanowires

Flexible visible-light photodetectors were fabricated by dispersing a large number of Sb₂Se₃ nanowires onto the Au interdigitated electrodes on PET substrates, which showed fast response speed and excellent flexibility.

Controlled Synthesis of Ultrathin Sb2Se3 Nanowires and Application for Flexible Photodetectors

A new solvothermal approach is introduced to synthesize ultrathin Sb₂Se₃ nanowires with diameters ranging from 10 to 20 nm and with length up to 30 μm. The Sb₂Se₃ nanowire-based photodetectors are firstly fabricated on polyethylene terephthalate and printing paper substrates, which exhibit excellent response to visible light with fast response time (0.18 and 0.22 s), high flexibility, and durability.

Recent developments in 2D layered inorganic nanomaterials for sensing

Two dimensional layered inorganic nanomaterials (2D-LINs) have recently attracted huge interest because of their unique thickness dependent physical and chemical properties and potential technological applications. The properties of these layered materials can be tuned via both physical and chemical processes. Some 2D layered inorganic nanomaterials like MoS2, WS2 and SnS2 have been recently developed and employed in various applications, including new sensors because of their layer-dependent electrical properties. This article presents a comprehensive overview of recent developments in the application of 2D layered inorganic nanomaterials as sensors. Some of the salient features of 2D materials for different sensing applications are discussed, including gas sensing, electrochemical sensing, SERS and biosensing, SERS sensing and photodetection. The working principles of the sensors are also discussed together with examples.

Liquid-solid spinodal decomposition mediated synthesis of Sb₂Se₃ nanowires and their photoelectric behavior

The convenient synthesis of one-dimensional nanostructures of chalcogenide compounds with a visible band-gap is an essential research topic in developing next-generation photoelectronic devices. In particular, the design of a theoretically predictable synthesis process provides great flexibility and has a considerable ripple effect in nanotechnology. In this study, a novel rational growth approach is designed using the spinodal decomposition phenomenon for the synthesis of the Sb2Se3 nanowires, which is based on the thermodynamic phase diagram. Using a stacked elemental layer (Sb/Sb-Se/Se) and heat treatment at 623 K for 30 min under an N2 atmosphere, the vertically inclined one-dimensional nanostructures are experimentally demonstrated. An additional annealing process at 523 K in a vacuum effectively removed excess Se elements due to their high vapor pressure, resulting in highly dense single crystal Sb2Se3 nanowire arrays. Adaption of our synthesis approach enables significantly improved photocurrent generation in the vertically stacked structure (glass/ITO/Sb2Se3 nanowires/ITO/PEN) from 6.4 (dark) to under 690 μA (at 3 V under AM 1.5G). In addition, a photoelectrochemical test demonstrated their p-type conductivity and robust photocorrosion performance in 0.5 M H2SO4.

Vibrational properties and bonding nature of Sb2Se3 and their implications for chalcogenide materials

There is more to chemical bonding in chalcogenides than the shortest, strongest bonds, as revealed by microscopic quantum-chemical descriptors.

Antimony selenide (antimonselite, Sb₂Se₃) is a versatile functional material with emerging applications in solar cells. It also provides an intriguing prototype to study different modes of bonding in solid chalcogenides, all within one crystal structure. In this study, we unravel the complex bonding nature of crystalline Sb₂Se₃ by using an orbital-based descriptor (the crystal orbital Hamilton population, COHP) and by analysing phonon properties and interatomic force constants. We find particularly interesting behaviour for the medium-range Sb···Se contacts, which still contribute significant stabilisation but are much softer than the “traditional” covalent bonds. These results have implications for the assembly of Sb₂Se₃ nanostructures, and bond-projected force constants appear as a useful microscopic descriptor for investigating a larger number of chalcogenide functional materials in the future.

Photoelectrochemically deposited Sb2Se3 thin films: deposition mechanism and characterization

Photoelectrochemically deposited (PED) Sb₂Se₃ thin films present interesting properties and performance. PED can enhance the electroreduction process, which will result in the settlement of the dilemma of compound semiconductor electrodeposition.