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Pristine tin selenide (SnSe) and copper (Cu) doped SnSe single crystals are grown by direct vapour transport technique. The energy dispersive X‐ray, X‐ray diffraction and Raman spectroscopic analysis of grown crystals show preferred stoichiometry having a single phase othorhombic SnSe. The electrical conductivity of SnSe and Cu doped SnSe are 24.24 and 106.06 S m−1 at 310 K respectively which increase as temperature increases. Carrier concentration of grown single crystals are evaluated by the Hall effect. Lattice thermal conductivity of pristine SnSe is 0.61 W mK−1, that decreased by copper doping to 0.44 W mK−1 at 310 K and for both the crystals it shows decrement as temperature increases to 483 K. Seebeck coefficient of the grown SnSe and Cu doped SnSe are positive and obtained values are 536.44 and 492.90 µV K−1 respectively at 310 K that confirm the p‐type semiconducting nature. Power factor, Figure of merit and thermoelectric compatibility factor of grown pristine SnSe is 0.25 × 108 µV mK−2, 0.005 and 0.02 Volt−1 respectively and shows improvement in Cu doped SnSe, i.e., 0.08 × 108 µV mK−2, 0.017 and 0.07 Volt−1 respectively at 310 K. This shows Cu doping in SnSe makes it an effective thermoelectric device contender. [ABSTRACT FROM AUTHOR]

Nanoscale defects can induce the effective modulation of carrier concentration, mobility, and phonon scattering to secure high thermoelectric performance in semiconductors. However, it is still limited to effectively controlling nanoscale defects in thermoelectric materials. Here, argon plasma bombardment is employed to introduce a large number of point defects and dislocations in microcrystalline SnSe powders, synthesized by a solvothermal method. After sintering these powders into polycrystalline bulk materials, bulk SnSe shows the ZT increasing by up to 66.7% (from 0.36 to 0.6 at 773 K). Through detailed micro/nanostructure characterizations and first‐principles calculations, the underlying mechanism is elucidated for the evaluation of thermoelectric performance. This work provides a deep understanding of the mechanism of nanoscale defects in modulating thermoelectric performance and presents experimental evidence and experience for the design and synthesis of efficient thermoelectric materials, making significant contributions to future green energy technologies. [ABSTRACT FROM AUTHOR]

Polycrystalline SnSe, renowned for its environmental sustainability, holds promise as a significant thermoelectric material, attracting considerable research attention. This study focuses on the thermoelectric properties of p-type polycrystalline SnSe doped with silver copper telluride (AgCuTe). Our experimental results conclusively show that the decomposition products of AgCuTe not only fill Sn vacancies but also act as acceptors, thereby introducing additional hole carriers. This leads to a notable improvement in both carrier mobility and concentration. Importantly, the thermal conductivity of the doped samples remains largely unchanged, as the lattice flattening strategy significantly boosts electrical performance without affecting lattice thermal conductivity. Ultimately, the doped sample Sn0.97Se-0.5%AgCuTe resulted in a power factor of 6.2 mW mK−1 and a peak ZT value of 1.4 at 798 K, representing a 109% improvement in ZT value. All samples exhibits superior stability and reproducibility, emphasizing its reliability for practical applications. [ABSTRACT FROM AUTHOR]

The assembly of 2D materials via vertical stacking has shown great advantages in modern device design, while the interface formed by two 2D materials also provides a new opportunity to tune various physical properties. Herein, the impact of homogeneous stacking on the thermal conductivity of 2D SnSe, a promising thermoelectric material, has been elucidated by solving the phonon‐Boltzmann transport equation with the first‐principles approach. SnSe bilayer and trilayer stacks, involving diverse interfacial configurations, are constructed to reveal potential modulation of in‐plane lattice thermal conductivity. Compared to the single‐layer counterpart, the result demonstrates a reduced thermal transport capacity in both the SnSe bilayer and trilayer due to van der Waals interaction, and the SnSe bilayer could exhibit a greater potential for thermoelectric applications due to the significantly suppressed phonon transport. Moreover, the interface effect can be further verified by the stacking‐dependent behavior of thermal conductivity, while the reduced thermal conductivity in SnSe stacks can be attributed to the decreased phonon relaxation time caused by interlayer interactions, implying great potential to further promote 2D SnSe‐based thermoelectric applications by stacking modulation. [ABSTRACT FROM AUTHOR]

In this study, Bi-doped SnSe was fabricated through the high energy ball milling and the hydrogen reduction of Bi2O3, and its thermoelectric properties were analyzed. The specimen with pure-Bi was fabricated as a control group and properties were compared. In the case of specimens with added Bi2O3, when sintering was performed in a hydrogen atmosphere, Bi2O3 with a high melting point was reduced to Bi with a relatively low melting point. At this time, because of the appearance of the liquid phase, the orientation of the (400) plane increased, and the density was improved. As a result, the change of SnSe to n-type was confirmed in the temperature range of 300 K - 773 K due to Bi doping. Additionally, when Bi2O3 was used instead of pure-Bi, the thermal conductivity, which is inversely proportional to the figure of merit, decreased, and the electrical conductivity increased, resulting in an improvement in the figure of merit.

The thermoelectric performance of SnSe strongly depends on its low-energy electron band structure that provides high density of states in a narrow energy window due to the multi-valley valence band maximum (VBM). Angle-resolved photoemission spectroscopy measurements, in conjunction with first-principles calculations, reveal that the binding energy of the VBM of SnSe is tuned by the population of Sn vacancy, which is determined by the cooling rate during the sample growth. The VBM shift follows precisely the behavior of the thermoelectric power factor, while the effective mass is barely modified upon changing the population of Sn vacancies. These findings indicate that the low-energy electron band structure is closely correlated with the high thermoelectric performance of hole-doped SnSe, providing a viable route toward engineering the intrinsic defect-induced thermoelectric performance via the sample growth condition without an additional ex-situ process.

Material selection for thermoelectric modules and generators presents a considerable challenge. In commercially available thermoelectric generators, alloys with a high percentage of doping element are used to achieve different semiconductor polarity. This introduces mechanical stresses to the system due to the varying thermal expansion rates. Previous studies have demonstrated that the semiconductor polarity of SnSe alloys can be altered through Sb or Bi doping. This paper outlines a modified, scalable and cost-effective direct synthesis process for SnSe alloys, employing Sb, Bi, Ag, Ni, In and Mg as dopants. Polarity switching in the synthesized materials was observed with Bi doping, occurring in similar regions as observed with monocrystalline Sb. Additionally, In doping led to a significant increase in the Seebeck coefficient. Doping elements exhibited minimal influence on the crystal lattice of the material, with only minor shifts in lattice parameters noted. Crystallography analysis revealed a significant preferred orientation, consistent with the material's documented propensity to form and align in layers, a characteristic observable even to the naked eye and confirmed through optical and electron microscopy. Furthermore, we have developed and thoroughly calibrated an in-house apparatus for determining the Seebeck coefficient of thermoelectric materials, based on the already published methodology, which describes a method for determining the electrical conductivity of disk- and rod-shaped samples. [ABSTRACT FROM AUTHOR]

In important applications, thermoelectric technology has been widely applied for precise temperature control in intelligent electronics. This work synthesized and characterized low-content copper-doped SnSe thermoelectric catalysts using an easy and effective hydrothermal method. It was discovered that doping increased the crystal plane spacing of SnSe, increased the carrier concentration, and improved the thermoelectric properties. The best degradation was attained at x = 0.0025. The thermoelectric degradation performance of low-dose copper-doped tin selenide Sn1−xCuxSe (x = 0, 0.0005, 0.001, 0.0015, 0.002, 0.0025, 0.003), for the degradation of methylene blue from organic wastewater at 75 °C, was examined. Our research indicates that by using this approach, we can create more high-performance catalysts. [ABSTRACT FROM AUTHOR]

Selenium selenide (SnSe) has attracted widespread attention because of its environmental friendliness and ultra-low lattice thermal conductivity. Single-crystal SnSe has been discovered to exhibit a high ZT value, but its mechanical qualities are weak and its manufacturing process is complicated, rendering it unsuitable for commercial usage. Polycrystalline SnSe is facile to synthesis; however, due to its weakened electrical performance, it has a poor thermoelectric property. In this study, polycrystalline SnSe samples are prepared using hydrothermal synthesis combined with vacuum sintering, and their thermoelectric properties are modulated using alkali metal element doping. [ABSTRACT FROM AUTHOR]

Tin selenide exhibits outstanding thermoelectric properties. Among its various forms, multicrystalline SnSe stands out as a more practical choice compared to single-crystal SnSe, owing to its straightforward chemical synthesis process, enhanced processability, and scalability. Herein, we synthesized p-type polycrystalline Sn 1−x Ag X Se bulk materials (x = 0, 0.01, 0.015, 0.02, 0.025, 0.03) using a simple hydrothermal and hot pressing method. Characterization methods such as XRD, Raman and XPS were used to demonstrate the successful doping of Ag+ into the SnSe matrix. When the doping concentration reached Sn 0.98 Ag 0.02 Se (x = 0.02), Ag+ reached the optimal concentration in the SnSe matrix, causing significant lattice distortion which increased phonon scattering and lowered the thermal conductivity, resulting in Sn 0.98 Ag 0.02 Se achieving ZT max = 1.14. However, when the doping concentration exceeded Sn 0.98 Ag 0.02 Se (x > 0.02), excess silver ions precipitated, partially acting as charge carriers, leading to a significant increase in electrical conductivity, resulting in Sn 0.97 Ag 0.03 Se having an electrical conductivity of 6860 s/m at 773 K. Compared to the pure phase, the electrical conductivity of Sn 0.97 Ag 0.03 Se increased by 259 %, and the ZT value of Sn 0.98 Ag 0.02 Se increased by 178%. This work demonstrates that Ag+ is an effective p-type dopant in the SnSe system and indicates that high ZT values in SnSe can be achieved through a simple, low-cost, and environmentally friendly method. [ABSTRACT FROM AUTHOR]

Thermoelectric materials can generate electric power from dissipating heat without releasing any undesirable chemicals. They thus can increase global energy efficiency and reduce the use of fossil fuels that are a major resource for generating electric energy, thereby concurrently addressing energy and environmental crises seriously threatening humanity. Increasing a thermoelectric figure of merit, ZT, of materials has been a prime goal in thermoelectrics because an efficiency of thermoelectric power generation has been low until very recently. The recent development of ultrahigh thermoelectric performance in polycrystalline SnSe‐based materials is one of the most prominent breakthroughs in the history of thermoelectrics. They show an exceptionally high ZT of ~3.1 at 783 K and average ZT of ~2.0 from 400 to 783 K, which are the highest for any bulk thermoelectric systems. Here we review the recent advances in SnSe thermoelectrics, greatly changing the paradigm of studies and applications of thermoelectric technology. [ABSTRACT FROM AUTHOR]

Paper-based devices have aroused researchers' enormous interest due to the increasing need for disposable flexible optoelectronic devices. Here, we used a straightforward painting method to integrate semiconducting materials on an A4 paper substrate to create high-performance photodetectors. A solvent-free 2D SnSe film painted on paper allowed electrons to separate from holes more effectively, thereby reducing the level of recombination between holes and electrons. The paper-based SnSe photodetectors that we prepared demonstrated a robust, sensitive response over a wide range of spectral ranges from ultraviolet (254 nm) to near-infrared (1550 nm). The devices were characterized by fast response times (rise time of 0.066 s and fall time of 0.066 s). A high-performance photodetector was achieved by combining a photoconductive and pyroelectric effect. Additionally, we constructed the carbon nanotube (CNTs) films as electrodes in order to form an ohmic contact between the carbon nanotubes and the semiconductor, and the photogenerated electrons were able to efficiently move through the carbon nanotubes. Our research could contribute to the development of flexible photodetection devices that are low-cost, eco-friendly, and disposable. [ABSTRACT FROM AUTHOR]

One prevalent class of thin films concerns SnSe (tin selenide), which is the primary focus of this research, with the aim of discovering cost-effective coatings for photovoltaic applications. The electrodeposition method was employed to successfully synthesize tin selenide thin films on glass substrates (ITO and FTO) utilizing the novel organophosphorus precursor [(Me2)3N3PSe]. Notably, this precursor has not been utilized in prior literature. Initial cyclic voltammetry (CV) analyses were performed to thoroughly investigate the electrochemical behavior of the tin and selenium redox systems within the electrolyte. The CV outcomes yielded crucial insights, guiding the establishment of a defined potential range (− 1.1 to − 1.2 V vs. SCE) for effective SnSe film electrodeposition. Films deposited within this potential range exhibited characteristic needle-shaped polycrystalline SnSe structures. Comprehensive analyses of the thin films' structural, microstructural, and morphological characteristics were conducted, employing X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS). The crystallites' size was determined using the Debye–Scherrer formula. Moreover, a systematic exploration of the impact of deposition potential and substrate type on various film properties was undertaken. The results from XRD and Raman spectroscopy confirmed the formation of an orthorhombic single-phase SnSe under different deposition potentials. SEM/EDS analysis revealed uniform element distribution for deposition potentials of − 1.1 V and − 1 V on ITO and FTO substrates, respectively. The investigation further extended to the optical properties of films on glass substrates (ITO and FTO). Optical data showed a direct optical band gap (Eg) ranging from 1.25 to 2.24 eV for ITO and 1.46 to 2.87 eV for FTO across a wide spectra range. These optical traits, significantly influenced by deposition potential and substrate type, hold promise. Particularly, SnSe thin films deposited on ITO substrates at − 1.1 V displayed distinct advantages for potential photovoltaic applications compared to samples on FTO substrates. [ABSTRACT FROM AUTHOR]

Tin selenide (SnSe) holds great potential for abundant future applications, due to its exceptional properties and distinctive layered structure, which can be modified using a variety of techniques. One of the many tuning techniques is pressure manipulating using the diamond anvil cell (DAC), which is a very efficient in situ and reversible approach for modulating the structure and physical properties of SnSe. We briefly summarize the advantages and challenges of experimental study using DAC in this review, then introduce the recent progress and achievements of the pressure-induced structure and performance of SnSe, especially including the influence of pressure on its crystal structure and optical, electronic, and thermoelectric properties. The overall goal of the review is to better understand the mechanics underlying pressure-induced phase transitions and to offer suggestions for properly designing a structural pattern to achieve or enhanced novel properties. [ABSTRACT FROM AUTHOR]

Metal–insulator transition has long been one of the key subjects in condensed matter systems. Herein, the emergence of a large energy gap (Eg, 0.8–1.0 eV) in Bi(110) two‐atomic‐layer nanoribbons grown on a SnSe(001) substrate is reported, which normally has an intrinsic semimetal‐like characteristic. The existence of this abnormally large Eg in Bi(110) is, however, determined by Bi coverage. When coverage is above ≈64 ± 2%, Eg vanishes, and instead, a Bi(110) semimetal‐like phase appears through a singular insulator–metal transition. Measurements using qPlus atomic force microscopy demonstrate that either insulating or semimetal‐like Bi(110) possesses a distorted black phosphorous structure with noticeable atomic buckling. Density function theory fully reproduces the semimetal‐like Bi(110) on SnSe(001). However, none of the insulating phases with this large Eg could be traced. Although the underlying mechanism of the large Eg and the insulator‐metal transition requires further exploration, experiments demonstrate that similar results can be achieved for Bi grown on SnS, the structural analog of SnSe, exhibiting an even larger Eg of ≈2.3 eV. The experimental strategy may be generalized to utilization of group‐IV monochalcogenides to create Bi(110) nanostructures with properties unachievable on other surfaces, providing an intriguing platform for exploring the interesting quantum electronic phases. [ABSTRACT FROM AUTHOR]

Research has been conducted on a solar cell utilizing Tin Selenide (SnSe) as the absorber material having a structure of n-CdS/p-SnSe/p+-CuInSe2/p++-WSe2 with CuInSe2 (CIS) current augmenting and WSe2 back surface field (BSF) layers. The various parameters in CdS, SnSe, CIS, and WSe2 layers have been adjusted methodically for the optimum output. Under the optimum conditions, the proposed n-CdS/p-SnSe solar cell showcases a power conversion efficiency (PCE) of 26.12 % with VOC = 0.788 V, JSC = 38.62 mA/cm2, and FF = 85.78 %. The PCE of the device enhances to 33.88 % with VOC = 1.09 V, JSC = 38.64 mA/cm2, and FF = 80.24 % owing to the incorporation of the WSe2 BSF layer. However, a conjunction of the CIS layer with the SnSe achieves a higher JSC of 42.54 mA/cm2 and a PCE of 36.45 %. These in-depth simulation findings demonstrate the enormous potential of the SnSe absorber with the CIS current boosting layer for the creation of a thin film solar cell that is both affordable and highly efficient.

Abstract The thermoelectric performance of SnSe strongly depends on its low-energy electron band structure that provides high density of states in a narrow energy window due to the multi-valley valence band maximum (VBM). Angle-resolved photoemission spectroscopy measurements, in conjunction with first-principles calculations, reveal that the binding energy of the VBM of SnSe is tuned by the population of Sn vacancy, which is determined by the cooling rate during the sample growth. The VBM shift follows precisely the behavior of the thermoelectric power factor, while the effective mass is barely modified upon changing the population of Sn vacancies. These findings indicate that the low-energy electron band structure is closely correlated with the high thermoelectric performance of hole-doped SnSe, providing a viable route toward engineering the intrinsic defect-induced thermoelectric performance via the sample growth condition without an additional ex-situ process. Graphical Abstract

Density functional theory (DFT) calculations have been used to investigate physical–chemical sensing of various proposed interfaces as SnSe@Graphene, SnSe2@Graphene, Graphene@SnSe@Graphene, and Graphene@SnSe2@Graphene, where dispersion corrections have been included to taken into account the vdW interactions between the layers. Initially, we predicted the electronic structures, mobility and carrier concentrations (cc) of SnSe and SnSe2 structures. Using different methodology, the outcomes have confirmed the semiconductor properties of SnSe and SnSe2 with indirect bandgap of 1.20 eV and 0.94 eV calculated by Generalized Gradient Approximation (GGA) and MetaGGA (MGGA) adopted with Perdew-Burke-Ernzerhof (PBE) functional, while hybrid Heyd-Scuseria-Ernzerhof (HSE) hybrid functional overestimated the experimental observations for both materials. Room temperature high mobility and cc have predicted by 126 × 103 cm2V−1 s−1 with cc of 1.3 × 1013 cm3 for a two layers SnSe and 69 × 103 cm2V−1 s−1 with cc of 4.2 × 1018 cm3 for three layers SnSe2. Optical absorption spectrum revealed that the presence of two peaks at 60 THz and 48 THz with the intensity of 89879 cm−1 and 34504 cm−1 for interfaces including two layers of graphene. More interestingly, dielectric constant calculations showed that the transfer of carriers between graphene layers and SnSe in Graphene@SnSe@Graphene interface with absorption peak shifted to 24 THz along the in-plane direction and negative dielectric constants in the range of 24–169 THz, showing the effect of light-trapping through plasmonic.

Metal–insulator transition has long been one of the key subjects in condensed matter systems. Herein, the emergence of a large energy gap (Eg, 0.8–1.0 eV) in Bi(110) two‐atomic‐layer nanoribbons grown on a SnSe(001) substrate is reported, which normally has an intrinsic semimetal‐like characteristic. The existence of this abnormally large Eg in Bi(110) is, however, determined by Bi coverage. When coverage is above ≈64 ± 2%, Eg vanishes, and instead, a Bi(110) semimetal‐like phase appears through a singular insulator–metal transition. Measurements using qPlus atomic force microscopy demonstrate that either insulating or semimetal‐like Bi(110) possesses a distorted black phosphorous structure with noticeable atomic buckling. Density function theory fully reproduces the semimetal‐like Bi(110) on SnSe(001). However, none of the insulating phases with this large Eg could be traced. Although the underlying mechanism of the large Eg and the insulator‐metal transition requires further exploration, experiments demonstrate that similar results can be achieved for Bi grown on SnS, the structural analog of SnSe, exhibiting an even larger Eg of ≈2.3 eV. The experimental strategy may be generalized to utilization of group‐IV monochalcogenides to create Bi(110) nanostructures with properties unachievable on other surfaces, providing an intriguing platform for exploring the interesting quantum electronic phases.

SnSe has been demonstrated a thermoelectric material with great application potential. In this paper, a series of SnSe0.95-x mol% MnCl2 samples were prepared by melting method combined with SPS sintering, and the effect of MnCl2 doping on the thermoelectric properties of n-type polycrystalline SnSe was studded. The results show that all the samples exhibit obvious anisotropy, and have better thermoelectric properties along the direction parallel to the sintering pressure. The increase of MnCl2 doping concentration causes the change of Sn phase content and the precipitation of SnCl2 phase in the sample, thus affecting the carrier concentration and mobility, and improving the conductivity and See beck coefficient of the samples after thermal exaction. In addition, the point defects and SnCl2 precipitation introduced by MnCl2 doping significantly enhance the phonon scattering and reduce the thermal conductivity of the materials. However, the thermal conductivity increases slightly with the increase of MnCl2 doping amount. As a result, the SnSe0.9--0.5 mol% MnCl2 sample obtains a maximum ZT value of 1.01 at 773 K, which Is nearly 22 times that of the undead sample. [ABSTRACT FROM AUTHOR]

SnSe has been demonstrated a thermoelectric material with great application potential. In this paper, a series of SnSe0.95-x mol% MnCl2 samples were prepared by melting method combined with SPS sintering, and the effect of MnCl2 doping on the thermoelectric properties of n-type polycrystalline SnSe was studded. The results show that all the samples exhibit obvious anisotropy, and have better thermoelectric properties along the direction parallel to the sintering pressure. The increase of MnCl2 doping concentration causes the change of Sn phase content and the precipitation of SnCl2 phase in the sample, thus affecting the carrier concentration and mobility, and improving the conductivity and See beck coefficient of the samples after thermal exaction. In addition, the point defects and SnCl2 precipitation introduced by MnCl2 doping significantly enhance the phonon scattering and reduce the thermal conductivity of the materials. However, the thermal conductivity increases slightly with the increase of MnCl2 doping amount. As a result, the SnSe0.9--0.5 mol% MnCl2 sample obtains a maximum ZT value of 1.01 at 773 K, which Is nearly 22 times that of the undead sample. [ABSTRACT FROM AUTHOR]

Piezoelectricity is the electric charge which accumulates in certain materials in response to mechanical stimuli, while piezoelectric nanogenerators (PENGs) converting mechanical energy into electricity can be widely used for energy harvesting and self-powered systems. The group IV–VI monochalcogenides may exhibit strong piezoelectricity because of their puckered C2v symmetry and electronic structure, making them promising for flexible PENG. Herein, we investigated the synthesis and piezoelectric properties of multilayer SnSe nanosheets grown by chemical vapor deposition (CVD). The SnSe nanosheets exhibited high single-crystallinity, large area, and good stability. The strong layer-dependent in-plane piezoelectric coefficient of SnSe nanosheets showed a saturated trend to be ∼ 110 pm/V, which overcomes the weak piezoelectric response or odd-even effects in other layered nanosheets. A high energy conversion efficiency of 9.3% and a maximum power density of 538 mW/cm2 at 1.03% strain have been demonstrated in a SnSe-based PENG. Based on the enhanced piezoelectricity of SnSe and attractive output performance of the nanogenerator, a self-powered sensor for human motion monitoring is further developed. These results demonstrate the strong piezoelectricity in high quality CVD-grown SnSe nanosheets, allowing for application in flexible smart piezoelectric sensors and advanced microelectromechanical devices. [ABSTRACT FROM AUTHOR]

The outstanding thermoelectric material, SnSe, is also known for its inferior mechanical properties, which bring great inconvenience for its application in thermoelectric devices. In this work, SnSe bulks were prepared via a sequential procedure of high-pressure synthesis (HPS), ball milling, and spark plasma sintering (SPS). The produced polycrystalline samples with a unique microstructure of tightly-bound quasi-equiaxed grains exhibited excellent mechanical properties. The Vickers hardness (HV), compressive strength (σc), and bending strength (σb) reached 1.1 GPa, 300 MPa, and 90 MPa, respectively, all of which are far superior to those of ordinary polycrystalline SnSe. Furthermore, the microstructures did not deteriorate thermoelectric performance. This work demonstrated an effective procedure to prepare polycrystalline microstructure-engineered SnSe materials, which not only show advantages in device applications but also shed light on property enhancement for other layer-structured thermoelectric materials.

Material selection for thermoelectric modules and generators presents a considerable challenge. In commercially available thermoelectric generators, alloys with a high percentage of doping element are used to achieve different semiconductor polarity. This introduces mechanical stresses to the system due to the varying thermal expansion rates. Previous studies have demonstrated that the semiconductor polarity of SnSe alloys can be altered through Sb or Bi doping. This paper outlines a modified, scalable and cost-effective direct synthesis process for SnSe alloys, employing Sb, Bi, Ag, Ni, In and Mg as dopants. Polarity switching in the synthesized materials was observed with Bi doping, occurring in similar regions as observed with monocrystalline Sb. Additionally, In doping led to a significant increase in the Seebeck coefficient. Doping elements exhibited minimal influence on the crystal lattice of the material, with only minor shifts in lattice parameters noted. Crystallography analysis revealed a significant preferred orientation, consistent with the material’s documented propensity to form and align in layers, a characteristic observable even to the naked eye and confirmed through optical and electron microscopy. Furthermore, we have developed and thoroughly calibrated an in-house apparatus for determining the Seebeck coefficient of thermoelectric materials, based on the already published methodology, which describes a method for determining the electrical conductivity of disk- and rod-shaped samples.

Treatment of organic wastewater is still a difficult problem to solve. In this paper, Cu-doped SnSe powder was synthesized by a convenient and efficient hydrothermal method. Meanwhile, the degradation effect of different doping concentrations of SnSe on methylene blue was investigated. It was found that at low doping concentrations, the degradation effect on methylene blue was not obvious because Cu was dissolved in the lattice of the SnSe matrix at low concentrations. As the doping concentration increased, SnSe changed from a layered structure to a nanocluster structure with reduced particle size, and a mixed phase of SnSe and Cu2SnSe4 appeared. In fact, the degradation effect on methylene blue was significantly enhanced, and we found that the catalytic degradation effect on methylene blue was best at a doping concentration of 10 wt.%. [ABSTRACT FROM AUTHOR]

Although low thermal conductivity and high band degeneracy bring promising thermoelectric performance to cubic SnSe, its preparation strategies remain elusive. Here, a series of Sn 1–2 x (AgBi) x Se samples are synthesized using the vacuum melting (1173 K) and spark plasma sintering (723 K) methods. Owing to the increased configurational entropy caused by AgBiSe 2 solid solution, the cubic structure is obtained when x exceeds 0.2. The optimized carrier concentration significantly enhances electrical conductivity (σ), and maximal σ of 350 Scm−1 is obtained in Sn 0.5 (AgBi) 0.25 Se. Combined with the low lattice thermal conductivity caused by the small sound velocity and strong anharmonicity, the figure of merit of 0.08 is reached in Sn 0.6 (AgBi) 0.2 Se at 500 K. The mechanical performances are also improved, and a high Vicker hardness of 1.5 GPa is obtained in Sn 0.4 (AgBi) 0.3 Se. This work demonstrates the importance of the configurational entropy in phase regulation and provides insights into the design of new thermoelectrics. [ABSTRACT FROM AUTHOR]

SnSe based compounds have attracted much attention due to the ultra-low lattice thermal conductivity and excellent thermoelectric properties. The origin of the low thermal conductivity has been ascribed to the strong phonon anharmonicity. Generally, the microstructures are also effective in scattering the phonons and further reducing the lattice thermal conductivity. In this work, the microstructures of undoped SnSe and Bi-doped Sn0.97SeBi0.03 have been investigated by transmission electron microscopy. A characteristic microstructure of lath-like grains has been observed in SnSe based compounds from perpendicular to the pressure direction. In addition, there exist a large quantity of low-angle grain boundaries and a high concentration of edge dislocations and stacking faults in the grains. All these microstructures result in lattice mismatch and distortion and can act as the phonon scattering centers, which broaden the understanding of the low thermal conductivity of SnSe based compounds. [ABSTRACT FROM AUTHOR]

SnSe with layered structure, as a member of 2D materials and transition metal chalcogenides, is a promising candidate of electrocatalyst for hydrogen evolution. Reduced graphene oxide (RGO) is an excellent substrate of electrocatalyst. In this work, SnSe nanosheets (NSs) had been prepared via liquid exfoliation, and the as-prepared SnSe NSs had been hybridized with RGO by a simple hydrothermal method. The SnSe/RGO hybrid shows superior hydrogen evolution reaction (HER) performance and charge transfer capability than SnSe NSs. In addition, it exhibits a superior HER performance in 1.0 M H2SO4 with overpotential of − 298.79 mV (vs. RHE) at a current density of 10 mA/cm2 and a Tafel slope determined to be only 97.56 mV/dec. Moreover, the SnSe/RGO hybrid as working electrode is provided with excellent durability, which is capable of maintaining working current for 10 h. As demonstrated above, relative high activity and stability and low price make the SnSe/RGO hybrid a promising electrocatalyst. [ABSTRACT FROM AUTHOR]

Recent studies have revealed the outstanding thermoelectric performance of Bi-doped n-type SnSe. In this regard, we analyzed the band parameters for Sn1−xBixSe (x = 0.00, 0.02, 0.04, and 0.06) using simple equations and the Single Parabolic Band model. Bi doping suppresses the carrier-phonon coupling while increasing the density-of-states effective mass. The n-type SnSe is known to have two conduction bands converge near 600 K. Bi doping changes the temperature at which the band convergence occurs. When x = 0.04, its weighted mobility maximized near 500 K, which indicated the possible band convergence. The highest zT of the x = 0.04 sample at mid-temperatures (473–573 K) can be attributed to the engineered band convergence via Bi doping.

Dye-sensitized solar cells (DSSC) are among the interesting generations of solar cells that require further research to achieve industrial production. Current platinum (Pt) counter electrodes used in DSSCs is expensive and should be replaced by cheaper materials. In this study, we propose the tin-selenide (SnSe) material prepared on ITO substrates by the electrodeposition method as a Pt replacement. Our prepared materials demonstrated excellent electrocatalytic behavior and charge transport with iodide/triiodide electrolyte that is confirmed by cyclic voltammetry and electrochemical impedance spectroscopy. Our best DSSC reached efficiency of 4.9% that was slightly lower than the DSSC fabricated with Pt counter electrode. Therefore, our study shows that the low cost and earth-abundant SnSe prepared by the electrodeposition method is a suitable replacement for Pt in DSSCs.

To overcome the high-power consumption and poor selectivity of gas sensors and achieve ppb level low concentration gas sensing is an urgent need to widely deploy sensors to establish an air quality monitoring application network. In this paper, a fish-mesh SnSe nanofibers with diameter of 100 nm prepared by uniaxial electrospinning was introduced and its gas sensitivity was studied. The gas sensor based on SnSe nanofibers showed excellent selectivity and high sensitivity (31.07) for low concentration (10 ppm) triethylamine at low temperature (160 °C), and a low detection base limit (500 ppb). Therefore, fish-mesh SnSe nanofibers provide a new strategy for the preparation of high-performance triethylamine sensors. [ABSTRACT FROM AUTHOR]

SnSe has attracted extensive attention due to its ultralow thermal conductivity and excellent thermoelectric properties. In this work, pressure‐induced thermoelectric properties of Pnma SnSe are investigated via first‐principles calculations. We uncover distinct energy isosurfaces topology transition of conduction band by applying pressure. The newly created conduction band valley caused by pressure has a distinct anisotropic shape compared to the old one. Inducing pressure can greatly enhance the anisotropy of electronic transport properties of the n‐type Pnma SnSe. Furthermore, the lattice thermal conductivity also exhibits anisotropic behavior under pressure due to a special collaged phonon mode. The pressure‐induced lattice thermal conductivity along the a‐axis shows a slower growth trend than that along the b‐axis and c‐axis. The optimal ZT value of the n‐type Pnma SnSe along the a‐axis can reach 1.64 at room temperature. These results would be helpful for designing the Pnma SnSe‐based materials for the potential thermoelectric and valleytronic applications. [ABSTRACT FROM AUTHOR]

The thermoelectric effect allows for the direct generation of potential gradients from the temperature gradient of the material, and this spontaneous formation of cathodes and anodes can greatly facilitate chemical reactions. Here, the thermoelectric conversion process of SnSe, which has proven to be the best thermoelectric material, and its catalytic effect in the degradation of methylene blue are studied. With excellent thermoelectric properties but no heavy metals contained, it is revealed that SnSe serves as a thermal catalyst for organic degradation. By manifestation of the UV absorption, the degradation efficiency of methylene blue is greatly enhanced with the help of SnSe as a catalyst, especially at high temperatures. By thermoelectric test and theoretical analysis, it is further demonstrated that the non‐equilibrium carriers of SnSe at high temperatures create a built‐in electric field along the temperature gradient, thereby contributing to electron transport during the degradation of methylene blue. These results show that SnSe has an outstanding degradation effect on methylene blue, providing a new pathway for the degradation of water pollution. [ABSTRACT FROM AUTHOR]

Semiconducting SnSe, an analog of black phosphorus, recently attracted great scientific interest due to a disputed report of a large thermoelectric figure of merit, which has not been reproduced subsequently. Here we concentrate on the low-temperature ground state. To gain a better understanding of the system, we present magneto-transport properties in high-quality single crystals of as-grown, lightly doped SnSe down to liquid helium temperatures. We show that SnSe behaves as a p-type doped semiconductor in the vicinity of a metal-insulator transition. Electronic transport at the lowest temperatures is dominated by the hopping mechanism. Negative magnetoresistance at low fields is well described by antilocalization, while positive magnetoresistance at higher fields is consistent with the shrinkage of localized impurity wavefunctions. At higher temperatures, a dilute metallic regime is realized where elusive T2 and B2 resistivity dependence is observed, posing a challenge to theoretical comprehension of the underlying physical mechanism. [ABSTRACT FROM AUTHOR]

A sandwich-type photoelectrochemical (PEC) immunosensor was constructed on a screen-printed electrode (SPE) using gold-coated tin selenide quantum dots (Au-SnSe QDs) to determine the carbohydrate antigen 19 9 (CA19-9). Water-soluble Au-SnSe QDs were prepared by coating low-cost SnSe QDs, prepared by reacting tin(II) 2-ethyl hexanoate with selenium ions (HNaSe) without needing to add an external capping agent (SnSe QDs). SnSe-based QDs were characterized using high-resolution transmission electron microscopy (HR-TEM) and dynamic light scattering (DLS). DSP (dithio-bis (succinimidyl propionate)) as a linker was attached on Au@SnSe QDs and conjugated with CA19-9 monoclonal antibodies (Ab2-DSP-Au@SnSE QD). For capture probe assembling, an Au nano-layer was electrochemically deposited on a SPE by HAuCl4 reduction using 12 cycles of cyclic voltammetry (0 to − 1.4 V) at the scan rate of 50 mV s−1, then covered by self-assembly of DSP and covalent conjugation of CA19-9 Ab1. Our developed PEC immunosensor showed a significant photoelectrochemical response, recorded using chronoamperometry (0.3 V), for the presence of CA19-9 antigen in serum samples under light irradiation, with a detection limit (LOD) of 0.0011 U mL−1 and a dynamic range of 0.005–100 U mL−1. The recovery of CA19-9 determination from serum samples was 101 to 113%. [ABSTRACT FROM AUTHOR]

Recent studies have revealed the outstanding thermoelectric performance of Bi-doped n-type SnSe. In this regard, we analyzed the band parameters for Sn1−xBixSe (x = 0.00, 0.02, 0.04, and 0.06) using simple equations and the Single Parabolic Band model. Bi doping suppresses the carrier-phonon coupling while increasing the density-of-states effective mass. The n-type SnSe is known to have two conduction bands converge near 600 K. Bi doping changes the temperature at which the band convergence occurs. When x = 0.04, its weighted mobility maximized near 500 K, which indicated the possible band convergence. The highest zT of the x = 0.04 sample at mid-temperatures (473–573 K) can be attributed to the engineered band convergence via Bi doping. [ABSTRACT FROM AUTHOR]

Tin selenide (SnSe) holds great potential for abundant future applications, due to its exceptional properties and distinctive layered structure, which can be modified using a variety of techniques. One of the many tuning techniques is pressure manipulating using the diamond anvil cell (DAC), which is a very efficient in situ and reversible approach for modulating the structure and physical properties of SnSe. We briefly summarize the advantages and challenges of experimental study using DAC in this review, then introduce the recent progress and achievements of the pressure-induced structure and performance of SnSe, especially including the influence of pressure on its crystal structure and optical, electronic, and thermoelectric properties. The overall goal of the review is to better understand the mechanics underlying pressure-induced phase transitions and to offer suggestions for properly designing a structural pattern to achieve or enhanced novel properties.

Abstract The thermoelectric effect allows for the direct generation of potential gradients from the temperature gradient of the material, and this spontaneous formation of cathodes and anodes can greatly facilitate chemical reactions. Here, the thermoelectric conversion process of SnSe, which has proven to be the best thermoelectric material, and its catalytic effect in the degradation of methylene blue are studied. With excellent thermoelectric properties but no heavy metals contained, it is revealed that SnSe serves as a thermal catalyst for organic degradation. By manifestation of the UV absorption, the degradation efficiency of methylene blue is greatly enhanced with the help of SnSe as a catalyst, especially at high temperatures. By thermoelectric test and theoretical analysis, it is further demonstrated that the non‐equilibrium carriers of SnSe at high temperatures create a built‐in electric field along the temperature gradient, thereby contributing to electron transport during the degradation of methylene blue. These results show that SnSe has an outstanding degradation effect on methylene blue, providing a new pathway for the degradation of water pollution.

K–Sn and K–Se batteries are expected to simultaneously realize synergistic reactions in a single electrode with high capacity and stability of energy storage performance. However, the difficulty of these reactions is realizing the stable storage of K–Sn and the redox reaction of Se in the electrode simultaneously. Therefore, it is expected to design a new electrode structure to solve the above problems. Herein, a multidimensional structure of SnSe is designed with enhanced performance. In this structure, SnSe nanoparticles are co-encapsulated by "inner" 3D graphene aerogel and "outer" nitrogen doped carbon (SnSe/3D RGO@NC). The "outer" nitrogen doped carbon could provide stronger reaction product adsorption affinity as well as improve the potassium energy storage. The "inner" and "outer" carbon materials could synergistically improve the electrical conductivity, promoting the redox kinetics of Se to achieve K–Se energy storage. Ex-situ test results indicate K–Sn reaction and the redox reaction of Se were formed in the electrode. Finally, this electrode provides excellent potassium storage reversibility (312 mAh·g−1 after 350 cycles with 0.016% capacity fading per cycle) and favorable rate (196 mAh·g−1 at 5 A g−1) with K–Sn and K–Se reaction process. This study could provide ideas for structural design to utilize synergistic reactions with enhanced electrochemical performance in individual battery system. Synergistic reactions of K–Se and K–Sn storage: multidimensional carbon structure realizes enhanced Se redox reaction and Sn alloying potassium storage simultaneously. [Display omitted] • A multidimensional carbon structure of SnSe (SnSe/3D RGO@NC) is designed to enhance its potassium storage performance. • The "inner" and "outer" carbon materials could synergistically improve the electrical conductivity, while promoting the K–Se and K–Sn storage reaction. • The "outer" nitrogen doped carbon could provide stronger adsorption affinity of K 4 Sn 23 /K 2 Se as well as improve the potassium energy storage. [ABSTRACT FROM AUTHOR]

17β-estradiol (E2) is an important natural female hormone that is also classified as an estrogenic endocrine-disrupting compound (e-EDC). It is, however, known to cause more damaging health effects compared to other e-EDCs. Environmental water systems are commonly contaminated with E2 that originates from domestic effluents. The determination of the level of E2 is thus very crucial in both wastewater treatment and in the aspect of environmental pollution management. In this work, an inherent and strong affinity of the estrogen receptor-α (ER-α) for E2 was used as a basis for the development of a biosensor that was highly selective towards E2 determination. A gold disk electrode (AuE) was functionalised with a 3-mercaptopropionic acid-capped tin selenide (SnSe-3MPA) quantum dot to produce a SnSe-3MPA/AuE electroactive sensor platform. The ER-α-based biosensor (ER-α/SnSe-3MPA/AuE) for E2 was produced by the amide chemistry of carboxyl functional groups of SnSe-3MPA quantum dots and the primary amines of ER-α. The ER-α/SnSe-3MPA/AuE receptor-based biosensor exhibited a formal potential (E0′) value of 217 ± 12 mV, assigned as the redox potential for monitoring the E2 response using square-wave voltammetry (SWV). The response parameters of the receptor-based biosensor for E2 include a dynamic linear range (DLR) value of 1.0–8.0 nM (R2 = 0.99), a limit of detection (LOD) value of 1.69 nM (S/N = 3), and a sensitivity of 0.04 µA/nM. The biosensor exhibited high selectivity for E2 and good recoveries for E2 determination in milk samples. [ABSTRACT FROM AUTHOR]

Optical anisotropy offers an extra degree of freedom to dynamically and reversibly regulate polarizing optical components, such as polarizers, without extra energy consumption and with high modulating efficiency. In this paper, we theoretically and numerically design broadband and incident-angle-modulation near-infrared polarizers, based on the SnSe, whose optical anisotropy is quantitatively evaluated by the complete dielectric tensor, complex refractive index tensor, and derived birefringence (~|Δn|max = 0.4) and dichroism (~|Δk|max = 0.4). The bandwidth of a broadband polarizer is 324 nm, from 1262 nm to 1586 nm, with an average extinction ratio above 23 dB. For the incident-angle-modulation near-infrared polarizer, the high incident angles dynamically and reversibly modulate its working wavelength with a maximum extinction ratio of 71 dB. Numerical simulations and theoretical calculations reveal that the considerable absorption for p light and continuously and relatively low absorption of s light lead to the broadband polarizer, while the incident-angle-modulation one mainly arises from the blue shift of corresponding wavelength of p light's minimum reflectance. The proposed novel design of polarizers based on SnSe are likely to be mass-produced and integrated into an on-chip system, which opens up a new thought to design polarizing optical components by utilizing other low-symmetry materials. [ABSTRACT FROM AUTHOR]

SnSe is a very strong anisotropic material; sometimes, strong anisotropy is unenviable for producing parts of thermoelectric (TE) devices. In order to study the efficient preparation of high-performance n-type polycrystalline SnSe with weak anisotropy, in this work, we combine mechanical alloying at 450 RPM for 10 h and spark plasma sintering at 773 K under 50 MPa pressure for the preparation of polycrystalline SnSe 0.95- x I x (x = 0,0.01,0.02,0.03) samples, and investigate the TE properties. The prepared samples show very weak anisotropy. With iodine doping, increased carrier concentration is observed, in agreement with DFT calculations. A peak ZT ≈ 1.02 at 723 K is observed with I-doping of x = 0.02, which is about 225% higher than that of undoped sample with ZT ≈ 0.31 at 723 K in parallel direction, mainly attributed to the enhanced power factor and about 56% reduced thermal conductivity from 0.68 Wm−1K−1 to 0.30 Wm−1K−1. TE properties in both directions are not much different, and the ratios of electrical and thermal conductivities in both directions are very close to unity. [ABSTRACT FROM AUTHOR]

In this work, we investigated the thermoelectric properties of SnSe (Tin Selenide) thin films onto SiO 2 /Si-wafer substrates as prepared by RF (radio frequency) magnetron sputtering technique. The sputtering conditions used base pressure below 5.5 10−4 Pa and working pressure at 0.93 Pa within the Ar atmosphere as a flow rate fixed 40 sccm. The RF sputtering power was applied at 80 W and sputtering time for 30 min. After thin film deposition, as-deposited thin films were annealed by the vacuum annealing method at 300–450 °C. The crystal structure, morphology and film thickness, and atomic composition of SnSe thin film were carried out by X-ray diffraction (XRD), the field emission scanning electron microscope (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS) techniques, respectively. The thermoelectric properties (electrical resistivity; ρ) and Seebeck coefficient; S) were measured by the ZEM-3 method to calculate the power factor (PF) value. The results showed that the as-deposited thin films had improved the crystallography of SnSe from amorphous to crystalline phases after thin films were annealed at a temperature range of 300–400 °C. At room temperature, the maximum power factor of 0.35 mW m˗1 K˗2 (ρ = 202 mΩ m and S = 165 μV K˗1) could be found to estimate the dimensionless Figure of Merit (ZT) values around 0.44 for annealing thin film sample at 400 °C. • RF magnetron sputtering fabricated SnSe thin films onto SiO 2 /Si-wafer substrates. • Amorphous SnSe thin film could be changed to crystalline through thermal annealing at 300–400 °C. • The annealing thin film sample at 400 °C showed the PF max of 0.35 mW m˗1 K˗2 to be estimated the ZT value of around 0.44. [ABSTRACT FROM AUTHOR]

Treatment of organic wastewater is still a difficult problem to solve. In this paper, Cu-doped SnSe powder was synthesized by a convenient and efficient hydrothermal method. Meanwhile, the degradation effect of different doping concentrations of SnSe on methylene blue was investigated. It was found that at low doping concentrations, the degradation effect on methylene blue was not obvious because Cu was dissolved in the lattice of the SnSe matrix at low concentrations. As the doping concentration increased, SnSe changed from a layered structure to a nanocluster structure with reduced particle size, and a mixed phase of SnSe and Cu2SnSe4 appeared. In fact, the degradation effect on methylene blue was significantly enhanced, and we found that the catalytic degradation effect on methylene blue was best at a doping concentration of 10 wt.%.

Materials that can efficiently convert heat into electricity are widely utilized in energy conversion technologies. The existing thermoelectrics demonstrate rather limited performance characteristics at room temperature, and hence, alternative materials and approaches are very much in demand. Here, it is experimentally shown that manipulating an applied stress can greatly improve a thermoelectric power factor of layered p‐type SnSe single crystals up to ≈180 µW K−2 cm−1 at room temperature. This giant enhancement is explained by a synergetic effect of three factors, such as: band‐gap narrowing, Lifshitz transition, and strong sample deformation. Under applied pressure above 1 GPa, the SnSe crystals become more ductile, which can be related to changes in the prevailing chemical bonding type inside the layers, from covalent toward metavalent. Thus, the SnSe single crystals transform into a highly unconventional crystalline state in which their layered crystal stacking is largely preserved, while the layers themselves are strongly deformed. This results in a dramatic narrowing in a band gap, from Eg = 0.83 to 0.50 eV (at ambient conditions). Thus, the work demonstrates a novel strategy of improving the performance parameters of chalcogenide thermoelectrics via tuning their chemical bonding type, stimulating a sample deformation and a band‐structure reconstruction. [ABSTRACT FROM AUTHOR]

Multilevel resistive switching in memristive devices is vital for applications in non-volatile memory and neuromorphic computing. In this study, we report on the multilevel resistive switching characteristics in SnSe/SrTiO3(STO) heterojunction-based memory devices with silver (Ag) and copper (Cu) top electrodes. The SnSe/STO-based memory devices present bipolar resistive switching (RS) with two orders of magnitude on/off ratio, which is reliable and stable. Moreover, multilevel state switching is achieved in the devices by sweeping voltage with current compliance to SET the device from high resistance state (HRS) to low resistance state (LRS) and RESET from LRS to HRS by voltage pulses without compliance current. With Ag and Cu top electrodes, respectively, eight and six levels of resistance switching were demonstrated in the SnSe/SrTiO3 heterostructures with a Pt bottom electrode. These results suggest that a SnSe/STO heterojunction-based memristor is promising for applications in neuromorphic computing as a synaptic device. [ABSTRACT FROM AUTHOR]