Search

According to the performance requirements, either bulk or nanocrystalline form of the material can be used for different types of device applications. In the present study, zirconium triselenide bulk crystals were grown by direct vapour transport technique. The energy-dispersive X-ray analysis (EDAX) confirms the purity of the grown crystals. The as-grown crystals and powder have been examined under Carl Zeiss optical microscope and scanning electron microscope (SEM) for morphological studies which revealed the evolution of crystalline phases of the material by the layered kind of growth mechanism. The transmission electron microscopy (TEM) with selected area electron diffraction (SAED) pattern analysis showed the grown crystals possess good crystallinity, whereas X-ray diffraction (XRD) analysis confirmed the monoclinic phase of the crystals. To study the effect of different wavelength sources (Blue-470 nm, Green-540 nm, Red-670 nm) on bulk zirconium trisulfide photodetectors, a pulse photo response experiment was carried out. The anisotropic behaviour is also revealed using the same sources. Various device parameters like responsivity, sensitivity, detectivity and external quantum efficiency (EQE%) were calculated. The highest responsivity and detectivity of 81.7 µA/W and 3.56 × 107 Jones were achieved for blue (470 nm) light source, respectively.

This research work consists of the ultrasonically synthesized Cu0.4Sn0.6Se nanoparticles and comprehensive photoresponse investigation of these nanoparticles-based thin film. The chemical composition, lateral morphology, phase structure and band-gap measurements were established by means of EDAX-Elemental Mapping, TEM-SAED, powder XRD and UV-DRS-PL measurements, respectively. The average size of the nanoparticles is determined by particle size analysis. Cu0.4Sn0.6Se ternary alloy nanoparticles-based photodetector is designed. The photoconducting behaviour is investigated under periodic 532 nm lase illumination of power intensity 10 mW/cm2. The device unveiled good photo-responsivity, specific detectivity and fast response. Rise time of 1.3 s and decay time of 2.0 s were reported with excellent photo-responsivity of 13.55 mA/W, detectivity of 1.98 × 1010 Jones and EQE of 2.50% for 1.5 V. The results demonstrated that Cu0.4Sn0.6Se nanoparticles possessed excellent optoelectronic properties and have potential applications for future optoelectronic devices.

Recently, transition metal dichalcogenide have gained significant attention from researchers due to their extraordinary optoelectronic properties. Here we evaluate the photodetection properties of highly crystalline nanosheets of MoS0.5Se1.5 synthesized by high yield sonochemical exfoliation technique. Constituent elements have been verified by EDAX. The results of powder XRD shows highly crystalline nature of nanosheets and XRD pattern is well indexed to 2H-hexagonal lattice structure with P63/mmc space group. Transmission Electron Microscopy is conducted in order to find the structural details for the nanosheets of MoS0.5Se1.5. Picked Field Electron Diffraction pattern indicated the highly crystalline existence of the nanosheets. Drop casting method was utilized to deposit thin film of MoS0.5Se1.5 nanosheets on ITO substrate. Efforts have been made to study the photoresponse of MoS0.5Se1.5 thin film using 670 nm light having power intensity 3mv/cm2. The intensify photoresponsivity of 1.62 mA/W and specific detectivity of 1.3*108 Jones is observed. The present findings suggest effective way to tune bandgap for producing high-performance optoelectronic device.

The CuSe nanoparticles are synthesized from direct vapor transport-grown CuSe compound using the sonochemical exfoliation technique. The chemical composition, crystalline phase, morphological analy...

The advancement of portable and flexible electronics that is integrated with multiple sensing functions has increasingly drawn considerable interest. The fabricated sensors would have the ability to sense multiple deformations like pressing, twisting and trivial vibrations such as pulses of wrist vibrations to mimic human skin. Presently, we implemented an easy, cost-effective and optimized fabrication technique for production of pressure sensors based on MoSe2 nanosheets coated on cellulose paper. The present sensor exhibits an incorporation of large pressure sensitivity of 18.42 kPa−1 in pressure range 0.001–0.5 kPa, 7.28 kPa−1 in pressure range 1–35 kPa and 2.63 kPa−1 in pressure range 40–100 kPa, working in broad pressure range (from 0.001 to 100 kPa) and long-term stability up to 200 deformation cycles at 2 kPa. The sensor showed excellent response towards the detection of vibrations of machines including cellular phone, compressor, etc. Besides, the sensor shows excellent environmental stability and exhibits immune piezo-resistive response to temperature variation.

The two-dimensional pristine tin selenide (SnSe), possessing desirable optical, thermal, electrical, and optoelectronic characteristics, is the future nanomaterial of technological applications. In...

Herein, we report the significantly enhanced humidity responsiveness of resistive devices based on two-dimensional SnSe2/MWCNT nanohybrids. The multifunctional humidity sensor was exploited to esta...

Photodetectors which can operate at low temperature with multiple configurations are building blocks for the future technology in the field of Photonics. In this work, we have investigated the low temperature anisotropic photoresponse of Re0.2Sn0.8Se2 ternary alloy grown by direct vapor transport (DVT) technique. The time-dependent photoresponse of the Re0.2Sn0.8Se2 ternary alloy is recorded at different temperatures ranging from 300 to 60 K. At 300 K, Re0.2Sn0.8Se2 ternary alloy shows excellent photoresponse in both parallel and perpendicular configurations. We have observed that the Re0.2Sn0.8Se2 ternary alloy retains its outstanding photoresponse ability even at a low temperature of 60 K, in both the parallel and perpendicular configurations. Moreover, the critical parameters related to photodetection properties such as photoresponsivity (Rλ), spectral detectivity (D*), and rise time are evaluated. Our work demonstrates the potential of Re-doped SnSe2 ternary alloys for optoelectronic devices function at low temperatures.

Flexible sensors based on two-dimensional layered materials have gained huge attention in the field of intelligent electronics. The cellulose based platform provides a cost-effective way for fabric...

2-D transition metal dichalcogenide (TMDC)-based heterostructures are promising active materials for high-performance optoelectronic devices. The low-cost, large-area, and high-quality fabrication ...

The WSe2 single crystals were grown by a high-yield vapor-phase synthesis technique. The grown crystals have 2H-hexagonal lattice structure with a P63/mmc space group. Excitonic resonances A′ and B...

The nanosized materials exhibit a great potential for high-performance electronics applications, and the knowledge of their optoelectronic properties is essential since they are closely related to efficient electron–hole pair generation and photodetection properties. The present work consists of the high-yield synthesis of CuxSn1–xSe (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) ternary alloy nanocrystals by sonochemical exfoliation technique and comprehensive photocatalytic investigation of these alloy engineered nanocrystals. The stoichiometry, chemical composition, morphology, phase, structure, bandgaps, vibrational properties, binding energy and oxidation states of the synthesized nanocrystals are characterized by EDAX, TEM, SAED, XRD, UV-DRS, photoluminescence (PL) and Raman spectroscopy. The synthesized CuxSn1–xSe nanocrystal samples have been evaluated for their photocatalytic activity by studying the degradation of methylene blue (MB) and crystal violet (CV) dyes under UV light irradiation. The present study reveals about material photoabsorption characteristics that these materials could be used as a promising heterogeneous photocatalyst for degradation of pollutant dyes under UV irradiation. Also, it demonstrates and highlights the further alloy engineering modification of CuxSn1–xSe nanocrystals would promote the photocatalytic activity for various environmental applications or not. Experiments have also been performed for understanding the stability and reusability of the photocatalyst.

Tin selenide (SnSe), a member of the IV-VI group, belongs to the layered transition metal chalcogenide (TMC) family. As TMCs are chemically inert, and have a binary layered structure of Sn-X (X = S, Se, Te) type, they are used widely in the areas of photovoltaic, electronic, and optoelectronic devices. In the present study, a direct vapor transport technique was used to grow single crystals. The synthesized crystals were examined with energy-dispersive analysis of x-rays, optical microscopy-scanning electron microscopy, and x-ray diffraction techniques to investigate the purity, surface morphology, and phase, respectively. The present work reports the use of a layered monochalcogenide single-crystal substrate for preparation of metal-semiconductor or Schottky junction devices. The In/p-SnSe Schottky diode was prepared by a thermal evaporation method. Analysis for the In/p-SnSe Schottky contact is based on the measurement of the current–voltage characteristics of the Schottky diode within the temperature range (313 K < T < 413 K). Characteristics were analyzed using thermionic emission theory and Schottky barrier diode parameters including barrier height, ideality factor, and series resistance, which were obtained and analyzed using a Ln (I)-V method and Cheung’s method. This work also reports the anisotropic current–voltage characteristics as well as the alteration in the Schottky barrier diode parameters at high temperature.

Atomically thin layers of transition metal dichalcogenides (TMDCs) have shown great promise for the applications in the field of optoelectronics. TMDCs have drawn huge attention of researchers in recent past due to their unique layer dependent properties. Here, we report the high yield synthesis of atomically thin MoS2 Nanosheets. The Nanosheets are synthesized by sono-chemical exfoliation technique. The exfoliated MoS2 have 2H-hexagonal lattice structure with P63/mmc space group. The Raman spectrum shows the resonances corresponding to A1g and E2g vibrational modes of 2H-MoS2. The lateral morphology of MoS2 Nanosheets is observed by transmission electron microscopy. The SAED pattern depicts the highly crystalline nature of Nanosheets. The absorption spectrum of MoS2 Nanosheets shows A and B excitonic resonances corresponding to direct inter-band transition at 1.82 eV and 2.0 eV, respectively. Moreover, the photo detector based on MoS2 Nanosheets is fabricated and studied under periodic 670 nm illumination of power intensity 3 mW/cm2. The fast response with enhanced photo responsivity of 16.93 mA/W and specific detectivity of 5.12 × 108 Jones is observed. Overall, the present findings demonstrate high yield synthesis of Nanosheets with good quality to be used for photodetector.

Transition metal dichalcogenides are being interest in study for their optoelectronic device applications. This is an upsurge in research efforts after realizing monolayer device structures. This article presents the use of vanadium dioxide phase transition from monoclinic to rutile for obtaining heterojunction to Schottky diode characteristic transition. I V characteristics of VO2/MoSe2 heterojunction diode has studied in the temperature range 303 K–343 K. The results reveal the rectifying nature of the junction at 303 K. As temperature increases, rectification decreases and swings towards Schottky junction characteristics due to MIT behaviour of VO2 thin film. The heterojunction has also investigated in dark condition and under the photo intensity ranging from 10 to 60 mW/cm2. The pronounced rise in forward and reverse current was observed when the junction was exposed under the light. The typical diode parameters such as ideality factor, saturation current, Richardson constant, and responsivity (R), sensitivity (S) and detectivity (D) are determined for the quantitative analysis of VO2/MoSe2 heterojunction. I V characteristics of the diode resemble to photodiode I V characteristics.

Ultrathin two-dimensional WSe2 has attracted huge attention due to its potential applications in future wearable electronics. Here, we demonstrate the flexible and high-performance photodetector us...

In order to produce high performance optoelectronic device, alloy engineering holds good promise as technique for synthesis of materials having excellent properties. The direct vapour transport grown V0.15Sn0.85Se2 multilayer crystals are employed for fabrication of high performance photodetector. The detector showed reproducible and stable performance towards white light and also exhibited efficient sensitivity towards variation of intensities ranging from 20 to 120 mW/cm2. Subsequently, the detector is exploited for its broadband response in spectral range 480 nm, 560 nm and 670 nm illuminations. In addition, the photoresponse of detector is also exploited in temperature range 140–300 K. Furthermore, the detector is investigated for variation in response in ambient air and vacuum (10−3 Torr). Overall, the detector exhibited efficient performance under variety of illuminations and in different conditions which is required for high performance device.

Recently, the humidity sensors have captivated huge attention for making human life more comfortable and to diagnose several diseases. Here, we reported the excellent humidity responsiveness of V0.5Sn0.5Se2 ternary alloy for human breath monitoring and touchless positioning interface. The resistive sensor based on direct vapour transport grown bulk crystal of V0.5Sn0.5Se2 ternary alloy is fabricated and explored for its static response in different humidity levels ranging from 20 to 90%. The sensor showed excellent dynamic switching characteristics between relative humidity of 20% and 90% with responsivity of 6.78%, response time of 3.2 s and recovery time of 2.3 s. Subsequently, the sensor is exploited for giant responsiveness for human breath monitoring and words recognitions. The sensor exhibited quite distinct response towards different words namely, “Pratik”, “Chetan” and “Mohit”. Besides, novel touch-less positioning interface is explained with respect to humidity variation. Overall, the results advocate development of resistive sensors for intended humidity, biomedical as well as for intelligent touch-less sensing applications.

The solar response ability and low-cost fabrication of the photoanode are important factors for the effective output of the photoelectrochemical system. Modification of the photoanode by which its ability to absorb irradiation can be manipulated has gained tremendous attention. Here, we demonstrated the MoSe2, WSe2, and MoSe2/WSe2 nanocrystal thin films prepared by the liquid-phase exfoliated and electrophoresis methods. Atomic force microscopy and high-resolution transmission electron microscopy show that the liquid exfoliated nanocrystals have a few layered dimensions with good crystallinity. Scanning electron microscopy demonstrated uniform distribution and randomly oriented nanocrystals, having a homogeneous shape and size. X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectra confirm the equal contribution of MoSe2 and WSe2 nanocrystals in the formation of the MoSe2/WSe2 heterojunction. Because of superior absorption of MoSe2/WSe2 heterojunction in the visible region and type-II heterojunction band alignment, in situ measurement of heterojunction electrode shows almost 1.5 times incident photo-to-current conversion efficiency and photoresponsivity in comparison to individual material electrodes. Our result clearly indicates the influence of heterojunction formation between liquid exfoliated nanocrystals on effective separation of photogenerated exciton and enhances charge carrier transfer, which leads to the improvement in photoelectrochemical performance. Liquid exfoliated nanosheet-based heterojunction is attractive as efficient photoanodes for the photoelectrochemical systems.

Since few years, sensing electronics based on metal oxide, carbon based materials, inorganic–organic hybrid materials have intensively exploited for biomedical applications. The performance of sensors most likely to be relies on high surface to volume ratio of primary sensing elements for better interactions. Monitoring dynamic response demands highly sensitive fast response sensors. Here we report for the first time, high performance sensors based on WSe2 nanosheets having extrinsic semiconducting behaviour as active resistive sensing material. The WSe2 nanosheets are synthesized by high yield sonochemical exfoliation technique and are characterized by TEM, absorption spectroscopy and Raman spectroscopy. Subsequently, WSe2 resistive sensor was fabricated and fast humidity sensing is demonstrated. The sensor was exploited for electronic listening towards human breathing, whistling and speaking. The novel touchless motion sensing applications are also demonstrated. The sensor shows excellent performance with better sensitivity and reproducibility due to optimized material properties and device configuration. Over all, the results advocate development of resistive sensors for biomedical as well as for intelligent touchless sensing applications.

The present investigation deals with the preparation of antimony doped molybdenum di-selenide (Sb0.1Mo0.9Se2) single crystals and its application for detection of UV–Visible radiation. The chemical composition of the crystals grown by direct vapor transport (DVT) technique is confirmed by Energy Dispersive Analysis of X-rays (EDAX), while the morphological analysis is carried out using optical microscopy and Scanning Electron Microscopy. The grown crystals are characterized by powder X–ray diffraction technique to evaluate the structural properties of the material and are compared with that of the pure MoSe2 crystals grown under similar conditions. The XRD analysis revealed the hexagonal structure of the crystals. The indirect optical band gap of 1.39 eV, Urbach energy and steepness parameter were determined by UV–Visible spectroscopy. The ability of pure and Sb doped MoSe2 crystals to be used as detectors of UV, Visible and IR radiations are studied by their pulsed photoresponse on exposure to a polychromatic source at varying intensities of illumination. Laser source (670 nm) having an intensity of 3 mW cm−2, UV radiation (320 nm) having an intensity of 20 mW cm−2 and IR radiation having an intensity of 120 mW cm−2 were used in the measurements. The effect of biasing voltage on the photoresponse has also been analyzed. The excellent detection properties of the grown crystals are revealed from the responsivity, specific detectivity and external quantum efficiency (EQE) of pure and Sb doped MoSe2 crystals. The effect of doping is clearly seen in the improvement of the detection properties of the crystals.

In order to exploit effect of Sb incorporation on properties of SnSe2, alloy engineering is performed in SbxSn1-xSe2 (x = 0, 0.1, 0.2, 0.3) ternary compounds. The single crystals are grown by direct vapour transport technique. The elemental composition and purity of as-grown compounds are characterized by EDAX. The optical microscopy and scanning electron microscopy show characteristic morphological features like helical spiral, layered structure, clean surface, etc. on surface of grown crystals. The powder X-ray diffraction shows that the pristine and Sb incorporated samples possess 2H-Hexahonal lattice structure. However, lattice parameters and unitcell volume are changed on incorporation of Sb in SnSe2 structure due to increase in microstrain. The Raman spectroscopy reveals SnSe2-type A1g vibrational mode and the corresponding peak is shifted on lower wavenumber side on increasing Sb content. The results confirm substitution of Sb(+5) on Sn(+4) lattice site in host network. The influence of alloy engineering on photo response is studied. The highest photocurrent of 1.88 μA, responsivity of 43.45 mAW−1, detectivity of 18.25 × 1011 Jones and EQE (%) of 47.28% are observed for X = 0.1 sample.

Absorption spectra of hexagonally structured, tellurium excess p-type cadmium telluride (CdTe) grown from vapour phase having conductivity 2.529 × 104 (Ω cm)−1 was studied in the range 700–880 nm. The existence of phonon-assisted indirect transition was confirmed. The direct and indirect bandgaps and the involved phonon energy were identified. The analysis revealed a band tailing and the presence of a strong internal electric field responsible for the tunnelling of charge carriers.

According to the performance requirements, either bulk or nanocrystalline form of the material can be used for different types of device applications. In the present study, zirconium triselenide bulk crystals were grown by direct vapour transport technique. The as-grown crystals and powder have been examined under Carl Zeiss optical microscope and scanning electron microscope for morphological studies which revealed the evolution of crystalline phases of the material by the layered kind of growth mechanism. The energy dispersive analysis of X-ray (EDAX) characterization confirms that no impurity is found in the resulting product except the desired material. To study the effect of different wavelength sources (Blue-470 nm, Green-540 nm, Red-670 nm) on bulk zirconium trisulfide photodetectors, pulsed photo response experiment was carried out. The anisotropic behaviour is also revealed using the same sources. Various device parameters like responsivity, sensitivity, detectivity and external quantum efficiency (EQE%) were calculated. The highest responsivity and detectivity of 81.7 µA/W and 3.56 × 1007 Jones were achieved for blue (470 nm) light source respectively.

The advancement of portable and flexible electronics that is integrated with multiple sensing functions has increasingly drawn considerable interest. The fabricated sensors would have the ability to sense multiple deformations like pressing, twisting and trivial vibrations such as pulses of wrist vibrations to mimic human skin. Presently, we implemented an easy, cost-effective and optimized fabrication technique for production of pressure sensors based on MoSe

High-performance electronics demand extremely sensitive piezo-resistive sensors with important features such as low-fabrication cost, easy implementation, low power consumption and high-pressure sensitivity over broad pressure range. Herein, we report a flexible piezo-resistive paper-based device functionalised by WSe

Transition metal dichalcogenides have demonstrated tremendous potential for their applications in optoelectronic devices. The present work highlights the growth of pristine MoTe2 crystals by Direct Vapor Transport (DVT) technique and their application as photo detectors. The crystal composition is confirmed by EDAX and TEM analysis. The fabricated photodetector was tested under illumination of 670nm laser source and the effect of different biasing voltages were studied. Typical detector parameters such as photocurrent (Iph), photoresponsivity (Rλ), Detectivity (D), Sensitivity (S), rise time (τrise) and decay time (τdecay) were evaluated for the detector.

We report the Raman spectroscopy of SbxSn1−xSe2 (x = 0, 0.1, 0.2, 0.3) single crystals in temperature range 78 K–468 K. The strong peak, assigning A1g-vibrational mode, is found. The frequency of A1g peak decreases on increasing Sb concentration. The downshift is observed on increasing the temperature from 78 to 468 K. For the quantitative analysis, temperature coefficient (χo), peak position at 0 K (ω0), Anharmonic constant (Г0), and peak broadening at 0 K (C) are computed from the temperature dependence of frequency and peak width. The present findings provide a good scientific significance to qualitative and quantitative analyses of transition metal dichalcogenides.

A detailed study of phonon properties of SbxGe1-xSe (x = 0.00 and 0.15) crystals is demonstrated here. DVT technique was employed for crystal growth. Powder XRD confirmed the phase-singularity and revealed the structural minutiae of the grown materials. The surface morphology of the crystals was studied under a high-resolution microscope. Room temperature Raman spectroscopy revealed a blue shift in the out-of-plane mode (B3g) and in-plane modes (Ag(1) and Ag(2)) of GeSe with Sb mixing. Further, the temperature-dependent Raman spectroscopy showed a monotonous red-shift and softening of modes as the temperature increases from 103 K to 298 K. The first order temperature coefficients for peaks B3g and Ag(2) are calculated. Shifting of modes pertaining to laser-power is also recorded for room temperature, and thermal conductivity of the crystals is determined. A strong anisotropy is found in the thermal conductivity for out-of-plane and in-plane modes for both crystals.

Cadmium based thin films including CdTe and CdSe show great potential for the use in the field of solar cells, optoelectronic and biomedical applications. This work gives a brief review of the preparation of CdSe, and CdTe films by using various deposition techniques. The chemical bath deposition method was used to deposit CdSe films using three precursors such as cadmium nitrate, cadmium sulfate and cadmium acetate are reported. Also, this article reviews on the experimental advances in electrodeposited of CdSe and screen printed cadmium telluride thin films. Various characterization techniques namely, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDAX), scanning electron microscopy (SEM), UV-Visible spectrophotometer (UV-Vis) were used in the present research work have been discussed.

This article presents systematic studies of SbXW1-XSe2 (X = 0, 0.1) single crystals grown by direct vapour transport technique. The purity and stoichiometry were tested by energy dispersive analysis of X-ray (EDAX). To explore lattice structure of grown compounds, powder X-ray diffraction was performed. A surface morphology of Sb0.1W0.9Se2 crystals was checked by optical microscope and scanning electron microscope. The transmission electron microscopy was also used to verify the crystallinity of grown samples. The variations of electrical resistivity parallel and perpendicular to c-axis were measured in the temperature range from 303 to 673 K. The results showed semiconducting behaviour and anisotropic charge conduction of grown single crystals. The n-type semiconducting nature was confirmed by Hall-effect measurements. The optical band gap was determined by UV–Visible-NIR spectroscopy. The Raman spectrum was also taken from grown SbXW1-XSe2 (X = 0, 0.1) single crystals using excitation of 785 nm. The obtained results suggest the substitutional doping of Sb+5 on W+4 lattice site.

The unique ternary compositions VxSn1-xSe2 (x = 0, 0.15, 0.25 and 0.5) have been grown in single crystal form by direct vapour transport technique. The as-grown crystals have been examined under Carl Zeiss optical microscope for morphological studies. The tiny flakes have also been observed by scanning electron microscope and it reveals the layered structure of as-grown ternary alloys. The powder XRD pattern infers hexagonal lattice structure with 2H poly type and P 3 ¯ m 1 space group. The XRD pattern shows shifting of diffraction peaks on higher angle side as content of vanadium (V) increases, confirms substitution of V-atoms on tin (Sn)-atom sites. Using transmission electron microscope, the nano-structures have been found in sono-chemically exfoliated samples. The selected area electron diffraction pattern has been obtained using 200 kV electron beam and reveals the single crystalline nature of VxSn1-xSe2 (x = 0, 0.15, 0.25 and 0.5) ternary alloys. The Raman spectra show SnSe2 type A1g and Eg vibrational modes and on increasing V content blue shift in A1g peak indicates that the V-atoms well substitutes on Sn-site.

The present work shows zirconium trisulphide (ZrS3) single crystals-based photodetector functionality synthesized through the Direct Vapor Transport (DVT) technique. The elemental-chemical, surface morphology, structural phase, crystallinity and vibrational modes of the crystals were analyzed using Energy Dispersive Analysis of X-rays (EDAX), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Raman Spectroscopy respectively. These characterizations revealed the pure and layered crystals grown having a monoclinic phase with good crystallinity. Time-dependent photo-response of the detector fabricated from ZrS3 single crystals possessing smooth surface was recorded under the illumination of white light for different incident illumination levels (20 mW/cm2 to 120 mW/cm2) at room temperature. Further, a low-temperature photo-response upto 100 K for the incident light intensity of 120 mW/cm2 was carried out to validate the stability and durability of the detector. Typical detector parameters like responsivity, detectivity, sensitivity and response times were calculated and their variations are studied thoroughly concerning incident intensity and low-temperature. Furthermore, owing to the layered structure of the material, the photo-response of the device was recorded in both parallel (⊥to c-axis) and perpendicular (║to c-axis) direction of the crystallographic b-axis and device parameters were calculated at the room as well as low temperatures. The device exhibited strong anisotropy that originated from the layered structure of the grown crystals and involved an anisotropic charge conduction mechanism at the room as well as low temperatures.

Group II-VI compound semiconductors are an important class of opto-electronic materials. They find important applications in detector and photovoltaic cell using both in bulk as well as thin film form. In this reference Cadmium Telluride thin films were prepared by screening printing technique and sintered at different temperatures in open environment. In this paper the comparative detailed analysis of transient photo response of CdTe (Cadmium Telluride) thin films sintered at three different temperatures are presented. For this pulsed photo-response was measured as function of three different intensity of illumination within range of 40–120 mW/cm2, along with three different applied bias voltages i.e. 10 V, 13 V and 15 V. From these photo-response analysis, different photo-response parameters e.g. photo-current at termination of illumination (Io), probability of escape of an electron from trap per second (p) and trap depth (Et) have been calculated and compared for all three films along with all three applied bias voltage and intensity of illumination. Estimation of rise and decay time is made from pulsed photo response curves and a comparative study is presented. It shows that photo-current is a strong function of intensity of illumination, sintering temperature and bias voltage. However, different photo-response parameters e.g. probability of escape of an electron from trap per second, trap depth, rise time and decay time are less dependent on sintering temperature. Observed value of long decay time is due to the process induced trap inclusion in the prepared samples which make these films suitable candidate for low processing cost solar cell material.

Background A few COVID-19 related retrospective studies have established that older age, elevated neutrophil-lymphocyte ratio (NLR), and decreased lymphocyte-CRP ratio (LCR) were associated with worse outcome. Herein, we aim to identify new prognostic markers associated with mortality. Methods We conducted a retrospective hospital cohort study on patients ≥ 18 years old with confirmed COVID-19, who were admitted to our hospital between 03/15/2020 and 05/25/2020. Study individuals were recruited if they had a complete CBC profile and inflammatory markers such as CRP, ferritin, D-dimer and LDH, as well as a well-defined clinical outcomes (discharged alive or expired). Demographic, clinical and laboratory data were reviewed and retrieved. Univariate and multivariate logistic regression methods were employed to identify prognostic markers associated with mortality. Results Out of the 344 confirmed COVID-19 hospitalized patients during the study period, 31 who did not have a complete blood profile were excluded; 303 patients were included in the study, 89 (29%) expired, and 214 (71%) were discharged alive. Demographic analysis was tabulated in Table 1. The univariate analysis showed a significant association of death with absolute neutrophil count (ANC, p=0.022), NLR (p=002), neutrophil-monocyte ratio (NMR, p=< 0.0001), LCR (p=0.007), lymphocyte-LDH ratio (LLR, p=< 0.0001), lymphocyte-D-dimer ratio (LDR, p=< 0.0001), lymphocyte-ferritin ratio (LFR, p=< 0.0001), and platelets (p=0.037) with mortality. With multivariable logistic regression analysis, the only values that had an odds of survival were high LDR (odds ratio [OR] 1.763; 95% confidence interval [CI], 1.20–2.69), and a high LFR (OR 1.136, CI 1.01–1.34). We further build up a model which can predict >85% mortality in our cohorts with the utilization of D-dimer (>500 ng/ml), Ferritin (>200 ng/ml), LDR (< 1.6), LFR (< 4) and ANC (>2.5). This new model has a ROC of 0.68 (p< 0.0001). Conclusion This retrospective cohort study of hospitalized patients with COVID-19 suggests LDR and LFR as potential independent prognostic indicators. A new model with combination of D-dimer, Ferritin, LDR, LFR and ANC, was able to predict >85% mortality in our cohort with ROC of 0.68, it will need to be validated in a prospective cohort study. Disclosures Jihad Slim, MD, Abbvie (Speaker’s Bureau)Gilead (Speaker’s Bureau)Jansen (Speaker’s Bureau)Merck (Speaker’s Bureau)ViiV (Speaker’s Bureau)

The optical, electrical and optoelectronic properties of tin selenide crystals are of immense significance for application in photodetectors and energy conversion and storage devices. The transition metal chalcogenides possess a layered structure that interacts with each other through van der Waal forces and can also offer sites for intercalation. The low molecular weight materials like GeSe and SnSe are found in an orthorhombic structure. In this article, the optical, electrical and optoelectronic properties of as-grown tin selenide crystals are investigated. The chemical composition of the crystals grown with the aid of direct vapour transport (DVT) technique is confirmed through energy Dispersive analysis of X-rays (EDAX), at the same time the morphological analysis is accomplished using optical microscopy and Scanning Electron Microscopy (SEM). The grown crystals are characterized by powder X-ray diffraction (XRD) method to assess the structural properties of the material. The XRD evaluation found out the orthorhombic structure of the crystals with the space group 2h16D (Pcmn) having lattice parameters a = 11.490 A, b = 4.440 A and c = 4.135 A. The crystallinity of grown samples was verified by transmission electron microscopy (TEM). The single crystalline nature of grown crystals was revealed by SAED pattern. The indirect optical band gap of 1.0065 eV, Urbach energy and steepness parameter are calculated utilising UV–VIS-NIR spectrophotometer. The optical absorption of as-grown SnSe crystals has been measured close to the fundamental absorption edge at room temperature. Both types of transitions, i.e. direct and indirect, are involved in the absorption process. Electrical transport properties like resistivity measurements (parallel and perpendicular path to the c-axis) had been carried out on these crystals within the temperature range 297–673 K. Anisotropy in resistivity measurements in both the directions, i.e. parallel and perpendicular direction to the c-axis was discovered. The p-type semiconducting nature was confirmed with the aid of Hall-effect measurements. For the photodetection properties of SnSe crystals, light source (670 nm) having an intensity of 3 mW/cm2 at distinctive biasing voltages is used. The outstanding detection properties are revealed from the responsivity, specific detectivity and external quantum efficiency (EQE) of pure SnSe crystals.

We demonstrate the high performance humidity sensor based on Sb0.1Sn0.9Se2 ternary alloy for intended applications in intelligent electronics. The sensor based on bulk crystal of Sb0.1Sn0.9Se2 ternary alloy was fabricated and was investigated under humid environment of relative humidity of 20 to 95%. The sensor showed responsivity of 15.60% for switching between relative humidity of 20% and 95%. Moreover, Sb0.1Sn0.9Se2 sensor is explored for electronic listening of human breathing, whistling and speaking. Besides, the sensor is exploited for touchless sensing. The sensing of humidity of human skin and wet cotton are also accomplished. Over all, the results advocate development of smart sensors for biomedical as well as for intelligent touchless sensing applications.

The tin selenide crystals with different proportions of Sn and Se were grown by a direct vapour-transport technique. The layer by layer growth of crystals from the vapour phase was promoted by screw dislocation mechanism. The powder X-ray diffraction (XRD) shows good crystallinity of grown compound. The XRD patterns of grown compounds are well-indexed to orthorhombic structure. In the off-stoichiometric compound, evidence of $$\hbox {SnSe}_{{2}}$$ secondary phase is observed due to excess of selenium. The morphological investigations were carried out using a Carl Zeiss optical microscope. The electron diffraction was also recorded from tiny flakes using a transmission electron microscope. The electrical resistivity both parallel and perpendicular to the c-axis was measured in the temperature range of 303–490 K and activation energy was also calculated using Arrhenius relation. The electrical study depicts the extrinsic semiconducting nature of grown compositions.

Semiconductors are an important category of materials involved in many applications in modern society. One such application revolves around the search for efficient and sustainable forms of energy, where in the use of semiconductors to assist conversion of light to electrical energy. Photoelectrochemical solar cell, though finding meagre application in energy harvesting through photovoltaic route, can be used as a tool to identify solid liquid interaction in presence of incident radiation to find out important material parameters. One such important parameter of PEC system is a flat band potential which relates bending of energy bands of semiconductor to develop a barrier separating photo- generated carriers. In this article, the authors have determined the flat-band potential of a crystalline semiconductor photoelectrode using the Mott–Schottky plot, which relates semiconductor–electrolyte interfacial capacitance to voltage. To demonstrate this approach we used a crystalline p-type NbSe2 semiconductor electrode having a bandgap of 1.42 eV in an electrolyte of 0.025M I2+0.1M K4[Fe(CN)6]+0.1M K3[Fe(CN)6] with redox potential of 0.28 V. LCR meter with a suitable equivalent circuit, was used to extract interfacial capacitance data (C), which was then plotted with the electrode voltage via the Mott–Schottky equation (C−2SC versus VSCE). From the x-axis intercept the flat-band potential was determined to be 0.66 V. The semiconductor parameter values come in the potential range of leading chalcogenides as a semiconductor crystals which can be suitable for photo electrochemical solar cell in the near future.

Transition metal chalcogenides have shown great potential in the field of solar cell fabrication owing to their strong light matter interactions and favourable band gap. Here in, chemical vapour transport grown NbSe2 crystals are exploited for their optoelectronic applications. The NbSe2 crystals are used for fabrication of working electrode of PEC solar cell. The PEC cell is tested by current-voltage characteristics in dark and illumination of power intensity 30 to 100 mW/cm2. Typical performance parameters such as efficiency, fill factor, short circuit current and open circuit voltage are calculated. Besides, photodetector based on NbSe2 crystal is fabricated and is tested under white light of 100 mW/cm2 intensity. The devices show good photoresponse, suggesting the intended application in field of optoelectronics.