Hexagonal single crystal nanosheets of Nd3+ doped PbI2 were effortlessly synthesized via microwave-assisted technique under a power of 700 W and in a duration of 15 minutes with a homogeneous ...morphology. X-ray diffraction, energy dispersive X-ray spectroscope, scanning electron microscope, FT-Raman, UV-Visible, photoluminescence and dielectric measurement were employed to study the product. High purity, single phase and presence of Nd3+ doping was confirmed. SEM study confirm the formation of nanorods and single crystal nanosheets of very few nanometers in size. Robust vibrational analysis has been carried out and the observed bands are assigned to the vibration modes of E21, A11, A12, 2E21 and 2E11, respectively. These bands are red-shifted when compare to the corresponding bulk values which indicate relaxed nanostructure formation and occurrence of confinement effect. The thickness of the synthesized single crystal nanosheets are found to be in the range of ~20 to 30 nm. The energy band gap was calculated and found to be 3.35, 3.34, 3.42 and 3.39 eV for pure, 1, 3 and 5% Nd3+ doped lead iodide, respectively. The clear blue luminescence has been observed at 440 nm and 466 nm when excited at 250 nm and 280 nm respectively. Dielectric and ac electrical conductivity was also measured and discussed.
Herein, the optoelectrical investigation of cadmium zinc telluride (CZT) and indium (In) doped CZT (InCZT) single crystals-based photodetectors have been demonstrated. The grown crystals were ...configured into photodetector devices and recorded the current-voltage (I-V) and current-time (I-t) characteristics under different illumination intensities. It has been observed that the photocurrent generation mechanism in both photodetector devices is dominantly driven by a photogating effect. The CZT photodetector exhibits stable and reversible device performances to 632 nm light, including a promotable responsivity of 0.38 AW
, a high photoswitch ratio of 152, specific detectivity of 6.30 × 10
Jones, and fast switching time (rise time of 210 ms and decay time of 150 ms). When doped with In, the responsivity of device increases to 0.50 AW
, photoswitch ratio decrease to 10, specific detectivity decrease to 1.80 × 10
Jones, rise time decrease to 140 ms and decay time increase to 200 ms. Moreover, these devices show a very high external quantum efficiency of 200% for CZT and 250% for InCZT. These results demonstrate that the CZT based crystals have great potential for visible light photodetector applications.
Development of Sm:CdS thin films based visible light photodetectors for optoelectronic devices.
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•Facile fabrication of Sm:CdS thin film photodetector was developed.•High responsivity ...of 1.01 AW−1 for Sm:CdS compare to pure (0.213 AW−1).•High specific photodetectivity was noted ∼ 2.21 × 1012 Jones for Sm:CdS.•Excellent photosensitivity of ∼ 4.9 × 103 compare to pure CdS (∼ 2.0 × 103).•Very high EQE of ∼257 % was observed for Sm:CdS compare to pure CdS.
Achievement of high-performance photodetectors based on CdS is a key field of research and challenge in the current scenario. Here, facile fabrication and characterization of novel samarium (1, 3 and 5 wt.% Sm)-doped CdS thin films for the photodetector applications have been demonstrated. The fabricated films show good crystallinity with crystallites size ranging 18–30 nm. The morphology and homogeneity of Sm-doping ingrown films were confirmed through scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX). Field emission SEM study reveals the low dimension nanograins formation and the films are free from voids and cracks. The effects of Sm-doping on linear and nonlinear optical properties of the fabricated thin films have been elucidated. The optical parameters such as refractive index, energy gap, susceptibilities were noticed to be reduced by Sm-doping in CdS thin films. An emission peak around 536 ± 14 nm was observed in PL spectra of pure CdS which was found to be shifted and quenched by Sm-doping. Finally, the photodetector performance of the fabricated thin films has been investigated for 532 nm laser light. The photodetector based on the 1 wt.% Sm:CdS shows an improved performance (higher responsivity of 1.01 AW−1, higher detectivity of 2.21 × 1012 Jones, excellent photosensitivity of ∼4.9 × 103, and very high external quantum efficiency (EQE) of 257 %) compared to pure CdS (responsivity of 0.213 AW−1, detectivity of 7.43 × 1011 Jones, photosensitivity of ∼2.0 × 103, and EQE of 249.70 %). These results propose a much simpler route to achieve high-quality CdS films for photodetector applications.
The g-C3N4/TiO2 nanocomposites (NCs) are fabricated by optimization of calcination and subsequent hydrothermal technique decorated with CeO2 nanoparticles (NPs) to build the g-C3N4/TiO2–CeO2 hybrid ...NCs. The chemical and surface characterizations of structural, morphological, elemental composition, optical, photo-degradation, HER performance and the DFT computation has been efficiently analyzed. The g-C3N4/TiO2–CeO2 composite photocatalysts (PCs) exhibit photocatalytic improved performance (∼97 %) for MB aqueous dye related to pristine g-C3N4 and g-C3N4/TiO2 composite PCs. The obtained k value of the g-C3N4/TiO2/CeO2 heterostructure composite PCs has around 0.0262 min−1 and 6.1, 2.6 and 1.5 times higher than to g-C3N4 (0.0043 min−1), g-C3N4/CeO2 (0.0099 min−1) and g-C3N4/TiO2 (0.0180 min−1) PCs respectively. Likewise, the synergistic probable S-scheme charge separation mechanism based on scavengers’ tests and other values, which leads to effective separation of photo-excited (e−-h+) pairs, whereas high degradation and more H2O molecules have photo-reduction to H2. The H2 evolution reaction (HER) and the electrochemical impedance spectroscopy (EIS) of the as-obtained samples were explored via electrochemical study. This exertion recommends that the rational strategy and building of g-C3N4/TiO2–CeO2 nano-heterostructures were beneficial for developing visible-light-driven recyclable PCs for ecological refinement.
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•CeO2 coupled g-C3N4/TiO2 photocatalyst was effectively prepared by a facile method.•Optimum degradation efficiency was 6.1 times higher than g-C3N4 under visible-light.•XPS and DFT study ensues a strong interface among Ti, Ce and O atoms into g-C3N4.•g-C3N4/TiO2/CeO2 S-scheme heterostructure exposed superior H2 production activity.•Also, good reusability for organic dye degradation and efficient HER performance.
Abstract
Defect engineering is a promising method for improving light harvesting in photocatalytic materials like Zinc sulphide (ZnS). By altering the S/Zn molar ratio during hydrothermal processes, ...Zn and S defects are successfully introduced into the ZnS crystal. The band structures can be modified by adding defects to the crystal structure of ZnS samples. During the treatment process, defects are formed on the surface. XRD and Raman studies are used for the confirmation of the crystallinity and phase formation of the samples. Using an X-ray peak pattern assessment based on the Debye Scherer model, the Williamson-Hall model, and the size strain plot, it was possible to study the influence of crystal defect on the structural characteristics of ZnS nanoparticles. The band gap (E
g
) values were estimated using UV–Vis diffuse spectroscopy (UV–Vis DRS) and found that the E
g
is reduced from 3.28 to 3.49 eV by altering the S/Zn molar ratio. Photoluminescence study (PL) shows these ZnS nanoparticles emit violet and blue radiations. In keeping with the results of XRD, TEM demonstrated the nanoscale of the prepared samples and exhibited a small agglomeration of homogenous nanoparticles. Scanning electron microscopy (SEM) was used to examine the surface morphology of the ZnS particles. Inductively Coupled Plasma Optical Emission Spectroscopy
(
ICP-OES) and X-ray photoelectron spectroscopy (XPS) were used to evaluate and validate the elemental composition. XPS results indicate the presence of defects on the prepared ZnS nanoparticles. For the investigation of vacancy-dependent catalytic activity under exposure to visible light, defective ZnS with different quantities of Zn and S voids are used as catalysts. The lowest S/Zn sample, ZnS0.67 and the highest S/Zn sample, ZnS3, show superior photocatalytic activity.
Lead iodide is one of the best room temperature radiation detector including applications in solar cell and photodetectors. Herein, we have fabricated the high-quality thin films of pure and Nd:PbI
2
...through a simple and cost-effective spin-coating route and investigated their key properties. X-ray diffraction study confirms the growth orientation of all films along
c
-axis/(001) plane and single phase of 2H-PbI
2
Polytypes with the crystallites of size in range of 21–31 nm. Further confirmation of growth and phase was carried out through FT-Raman analysis. EDX and SEM mapping was also carried out to confirm the Nd doping and its homogeneity in the films. SEM provides a clear view on the surface morphology of grown films and grain size was found in the range of 54–71 nm. Optical measurement shows high transparency, i.e., ~ 90% for grown films in visible to NIR region. The direct bandgap is observed to be enhanced with Nd doping from 2.45 to 2.58 eV; however, there is another bandgap which shows reduction with doping from 2.30 to 2.24 eV. This shows the possibility of existence of sub-energy bandgap in PbI
2
. The stable value of refractive index is evaluated ~ 2. The value of εʹ is found to varies from 4 to 27 in the energy range of 1–2.5 eV. Optical limiting behavior of all films was also studied at two lasers of
λ
= 532 nm and 632.8 nm. Moreover, a device fabrication was done for electrical study and found the resistivity increases from 5.14 × 10
8
Ω-cm for pure to 1.18 × 10
9
Ω-cm for 5% Nd-doped PbI
2
.
Er-doped CdO thin films are coated on FTO substrates using so-gel-spin coater technique. XRD studies confirm the polycrystalline nature of (111) orientation of the films. Crystallite size, ...dislocation density, and Lattice strain is calculated from XRD data and found that they are varying with doping percentage. AFM studies revealed homogeneous distributions of the nano-grains of 13–19 nm size. Energy dispersive spectroscopy and mapping analyses confirm the elemental composition. All the films are showing high transmission of nearly 80% in the visible spectrum. The calculated direct, indirect band gap values are changing with a variation of doping from 2.85 to 2.97 eV. At higher wavelength, the dielectric constant values are in the range of 20–80. The linear, third-order susceptibilities and nonlinear refractive index values are varying from 2 to 7, 1.6 × 10−13 to 5.41 × 10−13 esu and 1.39 × 10−12 to 8.1 × 10−11 esu respectively.
•Pure and Er doped high quality CdO films were deposited by low cost Spin coating technique.•EDX/SEM mapping confirm the doping of Er in CdO.•UV–Vis–NIR measurement confirms high optical transparency of pure and doped films about 80%.•AFM studies confirm the nano structured thin films.•Strong effect of Er doping on third order nonlinear properties are observed.
Na–Zn–CdS alloys nanostructure films with different doping concentration of Zn (Zn = 1, 2, 3 and 4 wt %) were developed. Structural investigation of films showed that the films have broadened peak at ...2θ angle ~26.53°along with cubic zinc blende structure. Grain size of films were found in few nanometer range, which was confirmed from SEM. The vibration spectra of films revealed the characteristics peaks of CdS which are centered at 308-301 cm−1 and first overtone at 604-613 cm−1. The band gap values were obtained in the range of 2.40–2.46 eV. A broadening in optical band gap was observed with increase in Zn concentration. Third-order nonlinear optical susceptibility χ(3) and refractive index n(2) were obtained over the range of 2.92 × 10−13-1.0 × 10−11 esu, and 6.78 × 10−12-7.22 × 10−10 esu, respectively. Photoluminescence spectra of films exhibited the band to band transition with deep level emission (DLE) within the range of 554–568 nm for all films.
NiO is an excellent contender for smart windows, electrochemical super capacitor and dye sensitized photocathode. Hence, thin films of NiO with different concentrations (1, 3, 5 and 7 wt%) of Cr ...doping has been fabricated by a facile and low cost technique. The analysis of effect of Cr concentrations on structural, vibrational, morphological, optical and nonlinear optical properties has been studied. X-ray diffraction study confirms that the fabricated films are of polycrystalline nature with cubic phase. The determination of structural parameters such as crystallite size, dislocation density, lattice strain and number of crystallites per unit area was done. The presence of Cr doping in NiO was confirmed by EDX analysis. The vibrational modes were studied by FT-Raman analysis. AFM topography was recorded for pure and Cr doped NiO films. The crystallite/grain size was found to be in the range of 36–40 nm (from X-ray) and 6–12 nm (from AFM). High optical transparency was observed from visible to near infrared region for all the deposited films which is ~ 70 to 85%. The direct and indirect optical band gap were calculated and the direct band gap is found in the range of 3.85–3.78 eV. The optical constants like linear and nonlinear refractive index
(
n
2
)
, optical dielectric constant and loss, optical and electrical conductivity, third order nonlinear optical susceptibility
(
χ
3
)
were calculated from reflectance and absorbance data. The values of
n
2
and
χ
3
are found to be of order of 10
−7
and 10
−9
esu, respectively.
This research communication presents a rapid and facile microwave-assisted synthesis of single crystalline nanosheets (SCNSs) of hexagonal lead iodide (PbI2) decorated with Au nanoparticles, a ...potential optoelectronics material. Homogeneous low dimensional AuNP decoration in PbI2 resulted in a new absorption band at ~604 nm and a shift in band gap from 3.23 to 3.00 eV. The significant enhancement of photoluminescent (PL) intensity observed in the AuNP-PbI2 SCNSs is attributed to the coupling of the localized surface plasmon resonanzce of AuNP leading to improved excitation and emission rates of PbI2-SCNSs in the region of the localized electromagnetic field. The Au-PbI2 SCNSs display a compelling increment in photoconductivity, and its fabricated photodetector showed a stable and switchable photo-response. Due to ease of synthesis and enhanced photoconductivity along with appealing PL features, Au-PbI2 SCNS has the potential to be used as a material of choice when fabricating an optoelectronic devices of high performance.
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