Shift Current Photovoltaics based on A Noncentrosymmetric Phase in in-plane Ferroelectric SnS

The shift current photovoltaics of group IV monochalcogenides have been predicted to be comparable to those of state-of-the-art Si-based solar cells. However, its exploration has been prevented from the centrosymmetric layer stacking in the thermodynamically stable bulk crystal. Herein, we stabilized the noncentrosymmetric layer stacking of tin sulfide (SnS) in the bottom regions of SnS crystals grown on a van der Waals substrate by physical vapor deposition and demonstrated the shift current of SnS by combining the polarization angle dependence and circular photogalvanic effect. Furthermore, 180° ferroelectric domains in SnS were verified through both piezoresponse force microscopy and shift current mapping techniques. Based on these results, an atomic model of the ferroelectric domain boundary was proposed. The direct observation of shift current and ferroelectric domains reported herein paves a new path for future studies on shift current photovoltaics. This article is protected by copyright. All rights reserved.

Lateral Integration of SnS and GeSe van der Waals Semiconductors: Interface Formation, Electronic Structure, and Nanoscale Optoelectronics

The emergence of atomically thin crystals has allowed extending materials integration to lateral heterostructures where different 2D materials are covalently connected in the plane. The concept of lateral heterostructures can be generalized to thicker layered crystals, provided that a suitably faceted seed crystal presents edges to which a compatible second van der Waals material can be attached layer by layer. Here, we examine the possibility of integrating multilayer crystals of the group IV monochalcogenides SnS and GeSe, which have the same crystal structure, small lattice mismatch, and similar bandgaps. In a two-step growth process, lateral epitaxy of GeSe on the sidewalls of multilayer SnS flakes (obtained by vapor transport of a SnS₂ precursor on graphite) yields heterostructures of laterally stitched crystalline GeSe and SnS without any detectable vertical overgrowth of the SnS seeds and with sharp lateral interfaces. Combined cathodoluminescence spectroscopy and ab initio calculations show the effects of small band offsets on carrier transport and radiative recombination near the interface. The results demonstrate the possibility of forming atomically connected lateral interfaces across many van der Waals layers, which is promising for manipulating optoelectronics, photonics, and for managing charge- and thermal transport.

Phase-Controllable Growth of Air-Stable SnS Nanostructures for High-Performance Photodetectors with Ultralow Dark Current

The epitaxial growth of low-dimensional tin chalcogenides SnX (X = S, Se) with a controlled crystal phase is of particular interest since it can be utilized to tune optoelectronic properties and exploit potential applications. However, it still remains a great challenge to synthesize SnX nanostructures with the same composition but different crystal phases and morphologies. Herein, we report a phase-controlled growth of SnS nanostructures via physical vapor deposition on mica substrates. The phase transition from α-SnS (Pbnm) nanosheets to β-SnS (Cmcm) nanowires can be tailored by the reduction of growth temperature and precursor concentration, which originates from a delicate competition between SnS-mica interfacial coupling and phase cohesive energy. The phase transition from the α to β phase not only greatly improves the ambient stability of SnS nanostructures but also leads to the band gap reduction from 1.03 to 0.93 eV, which is responsible for fabricated β-SnS devices with an ultralow dark current of 21 pA at 1 V, an ultrafast response speed of ≤14 μs, and broadband spectra response from the visible to near-infrared range under ambient condition. A maximum detectivity of the β-SnS photodetector arrives at 2.01 × 108 Jones, which is about 1 or 2 orders of magnitude larger than that of α-SnS devices. This work provides a new strategy for the phase-controlled growth of SnX nanomaterials for the development of highly stable and high-performance optoelectronic devices.

Hydrogen-Induced Conversion of SnS2 into SnS or Sn: A Route to Create SnS2 /SnS Heterostructures

The family of van der Waals (vdW) materials is large and diverse with applications ranging from electronics and optoelectronics to catalysis and chemical storage. However, despite intensive research, there remains significant knowledge-gaps pertaining to their properties and interactions. One such gap is the interaction between these materials and hydrogen, a potentially vital future energy vector and ubiquitous processing gas in the semiconductor industry. This work reports on the interaction of hydrogen with the vdW semiconductor SnS₂ , where molecular hydrogen (H₂ ) and H-ions induce a controlled chemical conversion into semiconducting-SnS or to β-Sn. This hydrogen-driven reaction is facilitated by the different oxidation states of Sn and is successfully applied to form SnS₂ /SnS heterostructures with uniform layers, atomically flat interfaces and well-aligned crystallographic axes. This approach is scalable and offers a route for engineering materials at the nanoscale for semiconductor technologies based on the earth-abundant elements Sn and S, a promising result for a wide range of potential applications.

Ultrathin tin sulfide field-effect transistors with subthreshold slope below 60 mV/decade

In this paper, we present for the first time a field-effect-transistor (FET) having a 10 nm thick tin sulfide (SnS) channel fabricated at the wafer scale with high reproducibility. SnS-based FETs are in on-state for increasing positive back-gate voltages up to 6 V, whereas the off-state is attained for negative back-gate voltages not exceeding -6 V, the on/off ratio being in the range 10²-10³depending on FET dimensions. The SnS FETs show a subthreshold slope (SS) below 60 mV/decade thanks to the in-plane ferroelectricity of SnS and attaining a minimum value SS = 21 mV/decade. Moreover, the low SS values can be explained by the existence of a negative value of the capacitance of the SnS thin film up to 10 GHz (for any DC bias voltage between 1 and 5 V), with the minimum value being -12.87 pF at 0.1 GHz.

Desulfurization-Induced Formation of Amorphized Substoichiometric Tin Sulfide for Super High-Rate Capacity and Degradation-Free Cycling of Na Ion Storage

This work reports an amorphization and partial desulfurization method to improve the performance of sulfide-based materials for Na⁺ storage. Specifically, the polypyrrole derived carbon coated amorphous substoichiometric tin sulfide supported on aminated carbon nanotubes (PPY-C@SnS_x /ACNTs) with amorphized and substoichiometric tin sulfide (SnS_x ) is synthesized by simply thermal annealing the PPY-C@SnS₂ /ACNTs. The PPY-C@SnS_x /ACNTs shows stable reversible capacities of 410.2 mAh g^-1 for Na⁺ storage at 0.1 A g^-1 and excellent rate capacities of 270.2, 235.5, 217.4, and 210.0 mAh g^-1 at 5.0, 10.0, 20.0, and 30.0 A g^-1 , respectively. Nearly zero drops on the reversible capacities can be observed when it is sodiated/desodiated at 2.0, 5.0, and 10.0 A g^-1 for up to 1000, 6500, 8000 cycles, respectively. Its outstanding rate capacities and degradation-free cycling stabilities mainly arise from the amorphized and substoichiometric structure of SnS_x , which improve the reversible capacities and Na⁺ diffusivities of the PPY-C@SnS_x /ACNTs. The density functional theory (DFT) calculations indicate that the partial desulfurization can improve the electric conductivity and promote the sodiation/desodiation of SnS_x . It explains why the PPY-C@SnS_x /ACNTs can exhibit high performance for Na⁺ storage well.

Phase-controlled synthesis of SnS2and SnS flakes and photodetection properties

Two-dimensional (2D) layered tin sulfide compounds including SnS₂and SnS have attracted increasing attention due to their great potential application in the fields of optoelectronics and energy storage. However, device development has been delayed by the lack of capabilities to synthesize large-scale and high-quality 2D tin sulfide. Here, a phase-controlled synthesis of SnS₂and SnS flakes with lateral size over 100 μm was successfully realized via a facile chemical vapor deposition method. The lateral size of flakes and phase transformation of SnS₂to SnS can be tuned via changing the synthesis temperature. Compared to the formation of the SnS₂phase at relative low temperature (<750 °C), the SnS phase is favorable at higher temperature. The phototransistor based on the as-prepared SnS₂and SnS exhibits excellent photoresponse to 405 nm laser, including a high responsivity (1.7 × 10⁶mA W^-1), fast response rates (rise/decay time of 13/51 ms), an outstanding external quantum efficiency (5.3 × 10⁵%), and a remarkable detectivity (6.24 × 10¹²Jones) for SnS₂-based phototransistor, and these values are superior to the most reported SnS₂based photodetectors. Although the responsivity (3390 mA W^-1) and detectivity (1.1 × 10¹⁰Jones) of SnS-based device is lower than that of the SnS₂phototransistor, it has a faster rise/decay time of 3.10/1.59 ms. This work provides a means of tuning the size and phase of 2D layered tin sulfide, and promotes the application of SnS₂in high-performance optoelectronic devices.

The microwave properties of tin sulfide thin films prepared by RF magnetron sputtering techniques

In this paper we present the microwave properties of tin sulfide (SnS) thin films with the thickness of just 10 nm, grown by RF magnetron sputtering techniques on a 4 inch silicon dioxide/high-resistivity silicon wafer. In this respect, interdigitated capacitors in coplanar waveguide technology were fabricated directly on the SnS film to be used as both phase shifters and detectors, depending on the ferroelectric or semiconductor behaviour of the SnS material. The ferroelectricity of the semiconducting thin layer manifests itself in a strong dependence of the electrical permittivity on the applied DC bias voltage, which induces a phase shift of 30 degrees mm^-1at 1 GHz and of 8 degrees mm^-1at 10 GHz, whereas the transmission losses are less than 2 dB in the frequency range 2-20 GHz. We have also investigated the microwave detection properties of SnS, obtaining at 1 GHz a voltage responsivity of about 30 mV mW^-1in the unbiased case and with an input power level of only 16μW.

Imaging Anisotropic Waveguide Exciton Polaritons in Tin Sulfide

In recent years, novel materials supporting in-plane anisotropic polaritons have attracted a great deal of research interest due to their capability of shaping nanoscale field distributions and controlling nanophotonic energy flows. Here we report a nano-optical imaging study of waveguide exciton polaritons (EPs) in tin sulfide (SnS) in the near-infrared (near-IR) region using scattering-type scanning near-field optical microscopy (s-SNOM). With s-SNOM, we mapped in real space the propagative EPs in SnS, which show sensitive dependence on the excitation energy and sample thickness. Moreover, we found that both the polariton wavelength and propagation length are anisotropic in the sample plane. In particular, in a narrow spectral range from 1.32 to 1.44 eV, the EPs demonstrate quasi-one-dimensional propagation, which is rarely seen in natural polaritonic materials. A further analysis indicates that the observed polariton anisotropy originates from the different optical band gaps and exciton binding energies along the two principal crystal axes of SnS.

Multilayer Lateral Heterostructures of Van Der Waals Crystals with Sharp, Carrier-Transparent Interfaces

Research on engineered materials that integrate different 2D crystals has largely focused on two prototypical heterostructures: Vertical van der Waals stacks and lateral heterostructures of covalently stitched monolayers. Extending lateral integration to few layer or even multilayer van der Waals crystals could enable architectures that combine the superior light absorption and photonic properties of thicker crystals with close proximity to interfaces and efficient carrier separation within the layers, potentially benefiting applications such as photovoltaics. Here, the realization of multilayer heterstructures of the van der Waals semiconductors SnS and GeS with lateral interfaces spanning up to several hundred individual layers is demonstrated. Structural and chemical imaging identifies {110} interfaces that are perpendicular to the (001) layer plane and are laterally localized and sharp on a 10 nm scale across the entire thickness. Cathodoluminescence spectroscopy provides evidence for a facile transfer of electron-hole pairs across the lateral interfaces, indicating covalent stitching with high electronic quality and a low density of recombination centers.

Vapor Phase Synthesis of SnS Facilitated by Ligand-Driven "Launch Vehicle" Effect in Tin Precursors

Extraordinary low-temperature vapor-phase synthesis of SnS thin films from single molecular precursors is attractive over conventional high-temperature solid-state methods. Molecular-level processing of functional materials is accompanied by several intrinsic advantages such as precise control over stoichiometry, phase selective synthesis, and uniform substrate coverage. We report here on the synthesis of a new heteroleptic molecular precursor containing (i) a thiolate ligand forming a direct Sn-S bond, and (ii) a chelating O^N^N-donor ligand introducing a "launch vehicle"-effect into the synthesized compound, thus remarkably increasing its volatility. The newly synthesized tin compound [Sn(SBut)(tfb-dmeda)] 1 was characterized by single-crystal X-ray diffraction analysis that verified the desired Sn:S ratio in the molecule, which was demonstrated in the direct conversion of the molecular complex into SnS thin films. The multi-nuclei (1H, 13C, 19F, and 119Sn) and variable-temperature 1D and 2D NMR studies indicate retention of the overall solid-state structure of 1 in the solution and suggest the presence of a dynamic conformational equilibrium. The fragmentation behavior of 1 was analyzed by mass spectrometry and compared with those of homoleptic tin tertiary butyl thiolates [Sn(SBut)2] and [Sn(SBut)4]. The precursor 1 was then used to deposit SnS thin films on different substrates (FTO, Mo-coated soda-lime glass) by CVD and film growth rates at different temperatures (300-450 °C) and times (15-60 min), film thickness, crystalline quality, and surface morphology were investigated.

Realization of Large Scale, 2D van der Waals Heterojunction of SnS2 /SnS by Reversible Sulfurization

2D van der Waals heterojunction provides an attractive opportunity for realizing novel electronic or optoelectronic devices. It remains challenging to realize high-quality heterostructures through scalable methods such as molecular epitaxy growth (MBE). Here, growth of few-layer SnS thin films is reported on mica and Nb-doped SrTiO₃ (100) substrates by MBE. Then the top layer of SnS film is uniformly sulfurized to monolayer SnS₂ in a sulfur atmosphere, resulting in a high-quality SnS₂ /SnS 2D heterojunction. Furthermore, the SnS₂ layer can be recovered to SnS by annealing SnS₂ /SnS without sulfur supply, indicating the heterojunction formation is reversible. The scanning tunneling spectroscopy measurements on SnS₂ /SnS heterostructure indicate the type-II band alignment in SnS₂ /SnS. The work provides a promising approach to construct artificial 2D heterojunctions with desired properties, which could be extended to other sulfide and selenide systems.

Boosting Formate Production from CO2 at High Current Densities Over a Wide Electrochemical Potential Window on a SnS Catalyst

The flow-cell design offers prospect for transition to commercial-relevant high current density CO2 electrolysis. However, it remains to understand the fundamental interplay between the catalyst, and the electrolyte in such configuration toward CO2 reduction performance. Herein, the dramatic influence of electrolyte alkalinity in widening potential window for CO2 electroreduction in a flow-cell system based on SnS nanosheets is reported. The optimized SnS catalyst operated in 1 m KOH achieves a maximum formate Faradaic efficiency of 88 ± 2% at -1.3 V vs reversible hydrogen electrode (RHE) with the current density of ≈120 mA cm-2 . Alkaline electrolyte is found suppressing the hydrogen evolution across all potentials which is particularly dominant at the less negative potentials, as well as CO evolution at more negative potentials. This in turn widens the potential window for formate conversion (>70% across -0.5 to -1.5 V vs RHE). A comparative study to SnOx counterpart indicates sulfur also acts to suppress hydrogen evolution, although electrolyte alkalinity resulting in a greater suppression. The boosting of the electrochemical potential window, along with high current densities in SnS derived catalytic system offers a highly attractive and promising route toward industrial-relevant electrocatalytic production of formate from CO2 .

Enhancing Reverse Saturable Absorption in SnS2 Nanosheets by Plasma Treatment

The knowledge concerning the influence of defects on the nonlinear optical response of materials remains scarce so far. In this work, we have successfully introduced defects into SnS₂ nanosheets by plasma treatment and shown that a defect generation is an effective approach to significantly improve the reverse saturable absorption of SnS₂. The SnS₂ nanosheets treated with Ar plasma for 40 s exhibit a nonlinear absorption coefficient (β₀) as large as (2.9 ± 0.12) × 10⁴ cm GW^-1, which is nearly 9 times that of the untreated sample. The influence of Ar-plasma-treatment time, defect type, and defect number on the nonlinear absorption of SnS₂ nanosheets are also studied. Structure and spectroscopy characterization confirms the introduction of S and Sn vacancies with Ar-plasma etching. Surface photovoltage spectroscopy and density functional theory calculation indicate that S vacancies can induce in-gap states in the band gap. These in-gap states act as intermediate states for the successive absorption of photons during femtosecond laser excitation (namely, excited-state absorption). In contrast, Sn defects cannot lead to in-gap states and have a limited contribution to nonlinear absorption. Our result would provide a promising way to improve optical nonlinearities.

SnS2 and SnO2 Nanoparticles Obtained from Organotin(IV) Dithiocarbamate Complex and Their Photocatalytic Activities on Methylene Blue

This work reports the photocatalytic degradation of methylene blue (MB) dye using SnS₂ and SnO₂ nanoparticles obtained from a solvothermal decomposition (in oleylamine) and pyrolysis (in a furnace) processes, respectively, of the diphenyltin(IV) p-methylphenyldithiocarbamate complex. The complex, which was used as a single-source precursor and represented as [(C₆H₅)₂Sn(L)₂] (L = p-methylphenyldithiocarbamato), was synthesized and characterized using various spectroscopic techniques and elemental analysis. The structural properties and morphology of the as-synthesized nanoparticles were studied using X-ray diffraction (XRD) technique and transmission electron microscopy (TEM). UV-visible spectroscopy was used to study the optical property. The hexagonal phase of SnS₂ and tetragonal SnO₂ nanoparticles were identified, which exhibited varying sizes of hexagonal platelets and rod-like morphologies, respectively. The direct band gap energies of both materials, estimated from their absorption spectra, were 2.31 and 3.79 eV for SnS₂ and SnO₂, respectively. The photocatalytic performances of the SnS₂ and SnO₂ nanoparticle, studied using methylene blue (MB) as a model dye pollutant under light irradiation, showed that SnO₂ nanoparticles exhibited a degradation efficiency of 48.33% after 120 min reaction, while the SnS₂ nanoparticles showed an efficiency of 62.42% after the same duration of time. The higher efficiency of SnS₂ compared to the SnO₂ nanoparticles may be attributed to the difference in the structural properties, morphology and nature of the material’s band gap energy.

Vertical Heterostructure of SnS-MoS2 Synthesized by Sulfur-Preloaded Chemical Vapor Deposition

We synthesize a vertical heterostructure (HS) between tin sulfide (SnS) and molybdenum sulfide (MoS₂) by chemical vapor deposition based on the preferential adsorption of sulfur on MoS₂. Most of the SnS grains nucleate on MoS₂ nanosheets, formatting partially stacked HS with large overlapping regions. Photoluminescence quenching of MoS₂ is observed and illustrates effective charge separation in HS. The HS shows increased reverse saturable absorption relative to MoS₂ and SnS. The preferential adsorption of sulfur powders on MoS₂ and HS growth reported herein will provide a promising approach to the synthesis of other two-dimensional HS.

Exciton-Driven Chemical Sensors Based on Excitation-Dependent Photoluminescent Two-Dimensional SnS

Excitation wavelength-dependent photoluminescence (PL) in two-dimensional (2D) transition-metal chalcogenides enables a strong excitonic interaction for high-performance chemical and biological sensing applications. In this work, we explore the possible candidates in the domain of post-transition-metal chalcogenides. Few-layered 2D p-type tin monosulfide (SnS) nanoflakes with submicrometer lateral dimensions are synthesized from the liquid phase exfoliation of bulk crystals. Excitation wavelength-dependent PL is found, and the excitonic radiative lifetime is more than one order enhanced compared to that of the bulk counterpart because of the quantum confinement effect. Paramagnetic NO₂ gas is selected as a representative to investigate the exciton-driven chemical-sensing properties of 2D SnS. Physisorption of NO₂ results in the formation of dipoles on the surface of 2D SnS, causing the redistribution of photoexcited charges in the body and therefore modifying PL properties. For practical sensing applications, 2D SnS is integrated into a resistive transducing platform. Under light irradiation, the sensor exhibits excellent sensitivity and selectivity to NO₂ at a relatively low operating temperature of 60 °C. The limit of detection is 17 parts per billion (ppb), which is significantly improved over other previously reported 2D p-type semiconductor-based NO₂ sensors.

Few-Layered Tin Sulfide Nanosheets Supported on Reduced Graphene Oxide as a High-Performance Anode for Potassium-Ion Batteries

Anodes involving conversion and alloying reaction mechanisms are attractive for potassium-ion batteries (PIBs) due to their high theoretical capacities. However, serious volume change and metal aggregation upon potassiation/depotassiation usually cause poor electrochemical performance. Herein, few-layered SnS₂ nanosheets supported on reduced graphene oxide (SnS₂ @rGO) are fabricated and investigated as anode material for PIBs, showing high specific capacity (448 mAh g^-1 at 0.05 A g^-1 ), high rate capability (247 mAh g^-1 at 1 A g^-1 ), and improved cycle performance (73% capacity retention after 300 cycles). In this composite electrode, SnS₂ nanosheets undergo sequential conversion (SnS₂ to Sn) and alloying (Sn to K₄ Sn₂₃ , KSn) reactions during potassiation/depotassiation, giving rise to a high specific capacity. Meanwhile, the hybrid ultrathin nanosheets enable fast K storage kinetics and excellent structure integrity because of fast electron/ionic transportation, surface capacitive-dominated charge storage mechanism, and effective accommodation for volume variation. This work demonstrates that K storage performance of alloy and conversion-based anodes can be remarkably promoted by subtle structure engineering.

C-Plasma of Hierarchical Graphene Survives SnS Bundles for Ultrastable and High Volumetric Na-Ion Storage

Tin and its derivatives have provoked tremendous progress of high-capacity sodium-ion anode materials. However, achieving high areal and volumetric capability with maintained long-term stability in a single electrode remains challenging. Here, an elegant and versatile strategy is developed to significantly extend the lifespan and rate capability of tin sulfide nanobelt electrodes while maintaining high areal and volumetric capacities. In this strategy, in situ bundles of robust hierarchical graphene (hG) are grown uniformly on tin sulfide nanobelt networks through a rapid (5 min) carbon-plasma method with sustainable oil as the carbon source and the partially reduced Sn as the catalyst. The nucleation of graphene, CN (with size N ranging from 1 to 24), on the Sn(111) surface is systematically explored using density functional theory calculations. It is demonstrated that this chemical-bonded hG strategy is powerful in enhancing overall electrochemical performance.

Contact and Noncontact Measurement of Electronic Transport in Individual 2D SnS Colloidal Semiconductor Nanocrystals

Colloidal-based solution syntheses offer a scalable and cost-efficient means of producing 2D nanomaterials in high yield. While much progress has been made toward the controlled and tailorable synthesis of semiconductor nanocrystals in solution, it remains a substantial challenge to fully characterize the products' inherent electronic transport properties. This is often due to their irregular morphology or small dimensions, which demand the formation of colloidal assemblies or films as a prerequisite to performing electrical measurements. Here, we report the synthesis of nearly monodisperse 2D colloidal nanocrystals of semiconductor SnS and a thorough investigation of the intrinsic electronic transport properties of single crystals. We utilize a combination of multipoint contact probe measurements and ultrafast terahertz spectroscopy to determine the carrier concentration, carrier mobility, conductivity/resistivity, and majority carrier type of individual colloidal semiconductor nanocrystals. Employing this metrological approach, we compare the electronic properties extracted for distinct morphologies of 2D SnS and relate them to literature values. Our results indicate that the electronic transport of colloidal semiconductors may be tuned through prudent selection of the synthetic conditions. We find that these properties compare favorably to SnS grown using vapor deposition techniques, illustrating that colloidal solution synthesis is a promising route to scalable production of nanoscale 2D materials.

Thickness-Dependently Enhanced Photodetection Performance of Vertically Grown SnS2 Nanoflakes with Large Size and High Production

Photodetection based on two-dimensional (2D) SnS₂ has attracted growing interest due to its superiority in response rate and responsivity, but high-quality growth and high performance photodetection of 2D SnS₂ still face great challenges. Here, high-quality SnS₂ nanoflakes with large-size and high-production are vertically grown on an Si substrate by a modified CVD method, having an average size of 30 μm with different thicknesses. Then a single SnS₂ nanoflake-based phototransistor was fabricated to obtain a high current on/off ratio of 10⁷ and excellent performance in photodetection, including fast response rates, low dark current, and high responsivity and detectivity. Specifically, the SnS₂ nanoflakes show thickness-dependent photodetection capability, and a highest responsivity of 354.4 A W^-1 is obtained at the average thickness of 100.5 nm. A sensitized process using an HfO₂ nanolayer can further enhance the responsivity up to 1922 A W^-1. Our work provides an efficient path to select SnS₂ crystal samples with the optimal thickness as promising candidates for high-performance optoelectronic applications.

Earth-Abundant Tin Sulfide-Based Photocathodes for Solar Hydrogen Production

Tin-based chalcogenide semiconductors, though attractive materials for photovoltaics, have to date exhibited poor performance and stability for photoelectrochemical applications. Here, a novel strategy is reported to improve performance and stability of tin monosulfide (SnS) nanoplatelet thin films for H₂ production in acidic media without any use of sacrificial reagent. P-type SnS nanoplatelet films are coated with the n-CdS buffer layer and the TiO₂ passivation layer to form type II heterojunction photocathodes. These photocathodes with subsequent deposition of Pt nanoparticles generate a photovoltage of 300 mV and a photocurrent density of 2.4 mA cm^-2 at 0 V versus reversible hydrogen electrode (RHE) for water splitting under simulated visible-light illumination (λ > 500 nm, P_in = 80 mW cm^-2). The incident photon-to-current efficiency at 0 V versus RHE for H₂ production reach a maximum of 12.7% at 575 nm with internal quantum efficiency of 13.8%. The faradaic efficiency for hydrogen evolution remains close to unity after 6000 s of illumination, confirming the robustness of the heterojunction for solar H₂ production.

Tin Sulfide-Based Nanohybrid for High-Performance Anode of Sodium-Ion Batteries

Nanohybrid anode materials for Na-ion batteries (NIBs) based on conversion and/or alloying reactions can provide significantly improved energy and power characteristics, while suffering from low Coulombic efficiency and unfavorable voltage properties. An NIB paper-type nanohybrid anode (PNA) based on tin sulfide nanoparticles and acid-treated multiwalled carbon nanotubes is reported. In 1 m NaPF₆ dissolved in diethylene glycol dimethyl ether as an electrolyte, the above PNA shows a high reversible capacity of ≈1200 mAh g^-1 and a large voltage plateau corresponding to a capacity of ≈550 mAh g^-1 in the low-voltage region of ≈0.1 V versus Na⁺ /Na, exhibiting high rate capabilities at a current rate of 1 A g^-1 and good cycling performance over 250 cycles. In addition, the PNA exhibits a high first Coulombic efficiency of ≈90%, achieving values above 99% during subsequent cycles. Furthermore, the feasibility of PNA usage is demonstrated by full-cell tests with a reported cathode, which results in high specific energy and power values of ≈256 Wh kg^-1 and 471 W kg^-1 , respectively, with stable cycling.

3D Porous Nanoarchitectures Derived from SnS/S-Doped Graphene Hybrid Nanosheets for Flexible All-Solid-State Supercapacitors

3D porous nanoarchitectures derived from SnS/S-doped graphene hybrid nanosheets are successfully prepared by controllable thermal conversion of oleylamine-capped mixed-phase SnS₂ -SnS nanodisks precursors, and employed as electroactive material to fabricate flexible, symmetric, all-solid-state supercapacitors. The fabricated solid devices exhibit very high areal specific capacitance (2.98 mF cm^-2 ), good cycling stability (99% for 10 000 cycles), excellent flexibility, and desirable mechanical stability.

Three-Dimensional Interconnected Spherical Graphene Framework/SnS Nanocomposite for Anode Material with Superior Lithium Storage Performance: Complete Reversibility of Li2S

Three-dimensional (3D) interconnected spherical graphene framework-decorated SnS nanoparticles (3D SnS@SG) is synthesized by self-assembly of graphene oxide nanosheets and positively charged polystyrene/SnO₂ nanospheres, followed by a controllable in situ sulfidation reaction during calcination. The SnS nanoparticles with diameters of ∼10-30 nm are anchored to the surface of the spherical graphene wall tightly and uniformly. Benefiting from the 3D interconnected spherical graphene framework and subtle SnS nanoparticles, the generated Li₂S could keep in close contact with Sn to make possible the in situ conversion reaction SnS + 2Li⁺ + 2e^- ↔ Sn + Li₂S. As a result, the 3D SnS@SG as the anode material for lithium ion batteries shows a high initial Coulombic efficiency of 75.3%. Apart from the irreversible capacity loss of 3D spherical graphene, the initial Coulombic efficiency of SnS in the 3D SnS@SG composite is as high as 99.7%, demonstrating the almost complete reversibility of Li₂S in this system. Furthermore, it also exhibits an excellent reversible capacity (800 mAh g^-1 after 100 cycles at 0.1 C and 527.1 mAh g^-1 after 300 cycles at 1 °C) and outstanding rate capability (380 mAh g^-1 at 5 °C).

A Two-Step Absorber Deposition Approach To Overcome Shunt Losses in Thin-Film Solar Cells: Using Tin Sulfide as a Proof-of-Concept Material System

As novel absorber materials are developed and screened for their photovoltaic (PV) properties, the challenge remains to reproducibly test promising candidates for high-performing PV devices. Many early-stage devices are prone to device shunting due to pinholes in the absorber layer, producing "false-negative" results. Here, we demonstrate a device engineering solution toward a robust device architecture, using a two-step absorber deposition approach. We use tin sulfide (SnS) as a test absorber material. The SnS bulk is processed at high temperature (400 °C) to stimulate grain growth, followed by a much thinner, low-temperature (200 °C) absorber deposition. At a lower process temperature, the thin absorber overlayer contains significantly smaller, densely packed grains, which are likely to provide a continuous coating and fill pinholes in the underlying absorber bulk. We compare this two-step approach to the more standard approach of using a semi-insulating buffer layer directly on top of the annealed absorber bulk, and we demonstrate a more than 3.5× superior shunt resistance Rsh with smaller standard error σRsh. Electron-beam-induced current (EBIC) measurements indicate a lower density of pinholes in the SnS absorber bulk when using the two-step absorber deposition approach. We correlate those findings to improvements in the device performance and device performance reproducibility.

SnS 3D Flowers with Superb Kinetic Properties for Anodic Use in Next-Generation Sodium Rechargeable Batteries

Tin sulfide (SnS) 3D flowers containing hierarchical nanosheet subunits are synthesized using a simple polyol process. The Li ion cells incorporating SnS 3D flowers exhibit an excellent rate capability, as well as good cycling stability, compared to SnS bulks and Sn nanoparticles. These desirable properties can be attributed to their unique morphology having not only large surface reaction area but also enough space between individual 2D nanosheets, which alleviates the pulverization of SnS.

Growth of Large-Size SnS Thin Crystals Driven by Oriented Attachment and Applications to Gas Sensors and Photodetectors

Freestanding large-size SnS thin crystals are synthesized via two-dimensional oriented attachment (OA) growth of colloidal quantum dots (CQDs) in a novel high-pressure solvothermal reaction. The SnS thin crystals present a uniform rectangular shape with a lateral size of 20-30 um and thickness of <10 nm. The evolution process demonstrates that a synergetic effect of pressure, aging time and organic ligands results in polycrystal-to-monocrystal formation and defect annihilation. Furthermore, gas sensor and photodetector devices, based on SnS thin single crystals, are also prepared. The sensing devices present high sensitivity, superior selectivity, low detection limit (≪100 ppb) and reversibility to NO2 at room temperature. The fabricated photodetector devices exhibit a high responsivity of 2.04 × 10(3) A W(1-) and high external quantum efficiency of ∼4.75 × 10(5) % at 532 nm, which are much higher than most of the photodetector devices.

Sandwich-like SnS/Polypyrrole Ultrathin Nanosheets as High-Performance Anode Materials for Li-Ion Batteries

Sandwich-like SnS/polypyrrole ultrathin nanosheets were synthesized via a pyrrole reduction and in situ polymerization route, in which room-temperature synthesized ZnSn(OH)6 microcubes were used as the tin source. As anode materials for Li-ion batteries, they exhibit an extremely high reversible capacity (about 1000 mA h g(-1) at 0.1C), outstanding rate capability (with reversible capabilities of 878, 805, 747, 652, and 576 mA h g(-1) at 0.2C, 0.5C, 1C, 2C, and 5C, respectively), stable cycling performance, and high capacity retention (a high capacity of 703 mA h g(-1) at 1C after long 500 cycles).

3.88% efficient tin sulfide solar cells using congruent thermal evaporation

Tin sulfide (SnS), as a promising absorber material in thin-film photovoltaic devices, is described. Here, it is confirmed that SnS evaporates congruently, which provides facile composition control akin to cadmium telluride. A SnS heterojunction solar cell is demons trated, which has a power conversion efficiency of 3.88% (certified), and an empirical loss analysis is presented to guide further performance improvements.

Synthesis and Size Dependent Reflectance Study of Water Soluble SnS Nanoparticles

Near-monodispersed water soluble SnS nanoparticles in the diameter range of 3-6 nm are synthesized by a facile, solution based one-step approach using ethanolamine ligands. The optimal amount of triethanolamine is investigated. The effect of further heat treatment on the size of these SnS nanoparticles is discussed. Diffuse reflectance study of SnS nanoparticles agrees with predictions from quantum confinement model.

Synthesis of SnS nanocrystals by the solvothermal decomposition of a single source precursor

SnS nanocrystals (NCs) were synthesized from bis(diethyldithiocarbamato) tin(II) in oleylamine at elevated temperature. High-resolution transmission electron microscopy (HRTEM) investigation and X-ray diffraction (XRD) analysis showed that the synthesized SnS particles are monocrystalline with an orthorhombic structure. The shape and size tunability of SnS NCs can be achieved by controlling the reaction temperature and time, and the nature of the stabilizing ligands. The comparison between experimental optical band gap values shows evidence of quantum confinement of SnS NCs. Prepared SnS NCs display strong absorption in the visible and near-infrared (NIR) spectral regions making them promising candidates for solar cell energy conversion.