Nanocrystalline CdS Thin Films Research Articles

Effect of Multilayers CdS Nanocrystalline Thin Films on the Performance of Dye-Sensitized Solar Cells

Due to relatively low price and nontoxicity of photovoltaic (PV) systems, dye-sensitized solar cells (DSSCs) recently gained a lot of attention in terms of improving their performance and longevity. Because most of the major elements are impacted by their separate production and layering procedures, the substances in DSSCs are critical to achieving these goals. Methylene blue dye sensitizer-based solar cells were effectively constructed in this work, and DSSC performance was assessed. The morphologies of nanocrystalline CdS thin films were investigated by the FE-SEM machine, and then XRD patterns of 1 layer, 2 layers, and 3 layers of nanocrystalline CdS thin films were analyzed. The thicknesses of the prepared samples were about 391 nm, 457 nm, and 912 nm for 1, 2, and 3 layers of nanocrystalline CdS thin film, respectively. J-V characteristics of the multilayer CdS thin films have been studied under a 100 mW/cm2 sunlight source. The experimental results revealed that the highest power conversion efficiency of a 3 layer porous-nanowall CdS/MB device was about 0.47%.

Nanocrystalline CdS thin films deposited by sol-gel spin coating method: Effect of aging and doping on structural, optical, and electrical properties

This work deals with the synthesization of pristine and Fe-doped CdS nanocrystalline thin films by the sol-gel spin coating method with the freshly prepared solution (Set-A) and 24 h aged solution (Set-B). The XRD patterns of pristine and Fe-doped nanocrystalline CdS thin films (Set-A) reveal hexagonal structure and the other films of set-B exhibit cubic structure. The average crystallite size of all pristine and Fe-doped nanocrystalline CdS thin films (Set-A and Set-B) was found to be lying in the range of 4.997–17.142 nm. The particle size calculated from TEM studies was found to be 11.14 nm, 10.74 nm and 8.74 nm for pristine, 2 ml Fe doped, and 5 ml Fe doped CdS thin films. The average surface roughness of the films was found to be 0.1518 nm, 4.2216 nm, and 0.1471 nm for Fe_00, Fe_01, and Fe_05 samples of Set-A, while it was found to be 0.2055 nm, 4.839 nm and 0.1803 nm for Fe_00, Fe_01 and Fe_05 samples of Set-B respectively. PL spectra reveal the occurrence of cyan emission for both sets of samples. The band gap values for the nanocrystalline thin films (Set-A) were 2.46–2.71 eV and for Set-B were in the range of 2.47–2.75 eV, which is higher than that of bulk CdS (2.42 eV). The low-temperature resistivity of the deposited films of both sets was obtained in the range of 105 to 103 Ω cm, and also found to decrease with increasing Fe concentration in CdS.

Spectroscopic Studies of CdS Nanocrystalline Thin Films Synthesized by Sol–Gel Spin Coating Technique for Optoelectronic Application: Influence of Co-Doping

Spectroscopic Studies of CdS Nanocrystalline Thin Films Synthesized by Sol–Gel Spin Coating Technique for Optoelectronic Application: Influence of Co-Doping

Structural and optical studies of nanocrystallined CdS

CdS nanocrystalline thin films have been prepared by sol-gel spin coating method. CdS nanoparticle thin films have been prepared using cadmium nitrate as cadmium source and thiourea as sulfur source. The effect of annealing on the properties of the prepared CdS nanocrystalline films has been studied. The x-ray diffraction studies indicated the formation of nanocrystalline CdS thin films with hexagonal phase. The grain size has been found to lie in the range of 5 to 8.2 nm depending on the annealing temperature suggesting the formation of CdS quantum dots. These results have been confirmed using high resolution transmission electron microscope (HRTEM) analysis which also indicated the formation of nanocrystalline CdS with a grain size of nearly 5 nm. The absorption spectra demonstrated the presence of quantum confinement effect in the prepared CdS nanocrystalline films because of the small size of the particles. The photoluminescence spectra of the CdS films exhibited green and yellow emission bands.

Preparation and Characterization of CdS and PbS Chalcogenides Compounds and n-CdS/p-PbS photodiode

In this study, a chemical bath deposition method (CBD) is used to synthesize CdS nanocrystalline thin films onto FTO substrate using two temperatures of 70 and 80 ºC for 1h of preparation time. PbS nanocrystalline thin films are also prepared using CBD using temperature of 35 ºC for 2h. XRD measurements confirmed that the prepared CdS and PbS thin films are polycrystalline with hexagonal phase for CdS and cubic for PbS. Scanning Electron Microscope images show increasing particles size of CdS thin films with increasing temperature of preparation and the films became more adherent on the substrates without pinholes or vacancies. Optical properties are investigated through UV-Visible Spectroscopy and found decreasing in the transmittance of prepared thin films with increasing temperature. Energy band gap calculated for CdS and PbS nanocrystalline thin films found with values higher than bulk value indicating to due to the quantum confinement effect. Photoluminescence spectra of prepared CdS nanocrystalline thin films appeared sharp emission beak at around 550 nm for all samples indicating high crystallinity. Photoresponse measurements of the fabricated photodetector showed a significant sensitivity to visible light at zero applied voltage, indicating that the fabricated device is a self-powered photodetector. The device was highly photosensitive of 16833, responsivity of 1.44 mAW−1, and a low rise/fall time of 0.284/0.298 s.

A comprehensive study of structural, optical and electrical properties of Cu doped CdS nanocrystalline thin films: for optoelectronic applications

A comprehensive study of structural, optical and electrical properties of Cu doped CdS nanocrystalline thin films: for optoelectronic applications

A systematic investigation on structural and optical properties of sol–gel spin coating fabricated CdS nanocrystalline thin films: effect of Ni doping

In the present work, we have successfully fabricated undoped and Ni-doped nanocrystalline CdS thin film on an ultrasonically cleaned glass substrate employing the sol–gel spin coating technique. The structural and spectroscopic properties of the films were investigated using XRD spectra, UV–Vis spectroscopy and photoluminescence spectra, respectively. The X-ray diffraction spectra revealed the polycrystalline nature of films with cubic structure and (111) as preferred orientation. The average crystallite size evaluated by the Debye–Scherrer formula lying in the range of 6–12 nm for the deposited films. According to UV–VIS Spectroscopy, the average transmittance of films in the visible region varies between 70–90%. The optical band gap of CdS thin film was evaluated from absorption spectra. The bandgap of the deposited films is in the range of 2.48–2.70 eV which is higher than that of bulk CdS (2.42 eV). This verifies the blue shifting in band edge of CdS nanocrystalline thin films due to the quantum confinement effect. Photoluminescence spectra of the thin film showed that the fundamental band edge emission peak centred at 485 nm also called blue band emission. It is observed that the low temperature resistivity of the films was in the range of 107–103 Ω cm and also found to decrease with increasing Ni concentration, as a result from dc two probe measurements.

Effect of Al-doping on the efficiency of chemically-deposited CdS/PbS thin film solar cells

Using chemical bath deposition in an ammonia-free system, CdS/PbS solar cells have been synthesized with different Al content in their composition and varying its absorber layer thickness. Nanocrystalline CdS thin-films with an average thickness of 140 nm were prepared and, subsequently, PbS thin-films with two different thicknesses (330 and 790 nm) were grown on the CdS. X-ray diffraction studies shows that CdS and PbS thin films have a hexagonal and cubic structure, respectively. The illuminated current/voltage characteristic curves of these p-n junctions were measured using a 300 W solar simulator at air mass 1.5, and a frequency of 50-60 Hz. It was found that Al doping decreases the conversion efficiency of the solar cells with the thinnest absorber layer, from 0.19 % to 0.05 %, and for those with thicker layers, from 0.19 % to 0.03 %.

Optical and structural of Nanocrystalline CdS

Nanocrystalline CdS thin films have been deposited using precursors with different thiourea concentration onto glass substrates by sol-gel spin coating method. The crystalline nature of the films has been observed to be strongly dependent on thiourea concentration and annealing temperature. The CdS films are found to be nanocrystalline in nature with hexagonal structure. The grain size is found to be in the range of 7.6 to11.5 nm depending on the thiourea concentration and annealing temperature. The high-resolution transmission electron microscopy (HRTEM) results of the CdS films prepared using cadmium to thiourea molar ratio of 0.3:0.3 indicate the formation of nanocrystalline CdS with grain size of 5 nm. Fourier transform infrared (FTIR) analysis shows the absorption bands corresponding to Cd and S. The optical study carried out to determine the band gap of the nanostructured CdS thin films shows a strong blue shift. The band gap energy has been observed to lie in the range of 3.97 to 3.62 eV following closely the quantum confinement dependence of energy on crystallite radius. The dependence of band gap of the CdS films on the annealing temperature and thiourea concentration has also been studied. The photoluminescence (PL) spectra display two main emission peaks corresponding to the blue and green emissions of CdS.

Enhancement in Visible Light Photoresponse of CdS Thin Films by Nitrocellulose Surface Passivation

Herein, we demonstrated a surface-passivated Ag/CdS/Ag photodetector device fabricated using nanocrystalline CdS thin films deposited via the spray pyrolysis method. Surface passivation with nitroc...

Vital role of Ar ambient pressure in controlled properties of nanocrystalline CdS thin films

A report on the manipulation of structural, optical, and electrical properties of nanocrystalline CdS (ncCdS) thin films in the framework of varying Ar ambient pressure in pulsed laser deposition (PLD) is presented here. Increase in Ar ambient pressure results in reduction of crystallite size which in turns increases the structural imperfections and structural phase transformation of ncCdS thin films. The most significant observation here is the bleaching of multiphonon Raman modes (MRMs) particularly LO + 2E2, 2LO + 2E2, etc. in ncCdS thin films. An acute investigation on the reason of bleaching of LO + 2E2, 2LO + 2E2, etc. modes is carried out here and concluded that it is due to the fading of E2 mode with increasing Ar pressure as confirmed by low-frequency micro-Raman measurements. UV–visible absorption and photoluminescence spectroscopies are used to examine the optical properties like bandgap and possible electronic transitions in ncCdS thin films. Further, transport properties of ncCdS thin films are investigated using Hall measurement and I–V characteristics.

Investigation of third-order nonlinear optical properties of nanostructured Ni-doped CdS thin films under continuous wave laser illumination

We report the third-order nonlinear optical (NLO) properties and optical limiting (OL) thresholds of pure CdS and Ni-doped CdS thin films have been investigated with the Z-scan technique under continuous wave laser excitation. Nanocrystalline CdS thin films with various doping concentrations of Ni (0%, 1%, 3%, 5% and 10 at.%) are prepared by spray-pyrolysis technique. XRD patterns reveal that all the prepared films are polycrystalline and the incorporation of Ni does not lead to major changes in the crystalline phase of Cd1−xNixS thin films. The surface morphology of the prepared films is impacted by the Ni-doping and is indicated by Field Emission Scanning Electron Microscopy (FESEM) images. With an increase in Ni-doping concentration, the energy band-gap value decreased from 2.48 eV to 2.23 eV. From the Z-scan data, it is observed that the material show strong two-photon absorption (2PA) and with an increase in Ni-doping concentrations from 0 to 10 at.%, the nonlinear absorption coefficient (β) are enhanced from 0.92 × 10−5 to 4.46 × 10−5 (cm W−1), nonlinear refractive index (n2) from 0.2967 × 10−9 to 0.1297 × 10−8 (cm2 W−1) and thereby the third-order NLO susceptibility (χ(3)) values also increased from 1.7075 × 10−6 to 7.4743 × 10−6 (esu). OL characteristics of the prepared films are studied at the experimental wavelength. The results propose that the Cd1−xNixS film is a capable material for nonlinear optical devices at 532 nm and optical power limiting applications.

Ga doping of nanocrystalline CdS thin films by electrodeposition method for solar cell application: the influence of dopant precursor concentration

Ga doping of CdS thin films has been achieved using a simplified cathodic electrodeposition method and with glass/indium tin oxide (glass/ITO) as a substrate. CdCl2, Na2S2O3 and GaCl3 were used as precursors. The Ga-doped and un-doped CdS films obtained were characterized for their structural, optical, luminescence, compositional and morphological properties using state-of-the-art X-ray diffraction (XRD), spectrophotometry, room-temperature photoluminescence (PL), energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM), respectively. XRD results show that the presence of Ga ions in the deposition electrolyte and post-deposition annealing promote crystallinity of deposited CdS films, with estimated crystallite sizes of the films in the range (5–22) nm after annealing. Optical characterization results show that incorporation of Ga atoms into the crystal lattice of CdS results in increase in energy bandgap of the films, which makes them advantageous for application as window/buffer layers in solar cells. PL results show a single green emission peak whose intensity increases as Ga-content of the films increases. EDX results show a direct relationship between the percentage atomic Ga composition of the CdS:Ga films and the molar concentration of GaCl3 in the deposition electrolyte. SEM images reveal smooth surfaces of doped and un-doped CdS films. However, after annealing, cracks begin to develop in the films grown with electrolytic GaCl3 concentration in excess of 0.004 M, thus indicating a possible threshold in GaCl3 concentration for obtaining device-grade CdS:Ga films. The entire work presents one of the strengths of electrodeposition as a reliable semiconductor growth technique for device application.

Morphological evolution in nanocrystalline CdS thin films from flowers to salt rock like structures

Surface morphological evolution is observed in thermally activated nanocrystalline CdS (nc-CdS) thin films. The chemical bath deposited nc-CdS thin films show flower like structures on micro-crack background. Thermal annealing of nc-CdS thin films at different temperatures viz. 300, 350, 400 and 450 °C for 3 h in Ar ambient developed surface morphology towards salt rock like structures with clear particle boundaries at higher temperatures. Besides, structural phase transition from zincblende to wurtzite is observed, at 350 °C in nc-CdS thin films. It is observed that on increasing the annealing temperature longitudinal optical phonon Raman mode shifts toward higher frequency side in either of the crystal structure and bandgap reduces. Photoluminescence study illustrates thermally activated enhancement in green emission and disappearance of yellow and red emission in both the structures. The variation in emission intensity is described on the bases of morphology and structural changes occur due to thermal activation.

Spectroscopic Ellipsometry and Optical Dispersion Analysis of Nanocrystalline CdS Thin Films

This study reports on spectroscopic ellipsometry (SE) and optical dispersion analysis of chemically deposited CdS thin films. The CdS thin films were prepared using chemical bath deposition and annealed in N2 atmosphere at temperatures of 100, 200, 300, and 500 °C for 60 min. The optical constants of nanocrystalline CdS thin films were investigated with SE. The ellipsometric parameters of the CdS thin films were measured with SE in the photon energy range from 1.24 to 6.48 eV. To investigate the dispersion parameters, the dispersion of the refractive index of the thin films was analyzed using the Wemple–DiDomenico single-oscillator model (W–D model) and the Sellmeier model. The optical dispersion parameters of the oscillator energy, the dispersion energy, the average oscillator strength, and the average oscillator wavelength of CdS thin films were investigated. In addition, dispersion parameters of CdS thin films were investigated as a function of the annealing temperature. The dispersion parameters of CdS thin films by the W–D model and Sellmeier model change with annealing temperature, which causes the transformation of the crystal structure.

Ion beam assisted fortification of photoconduction and photosensitivity

A new approach to substantially improve UV/Visible photo sensitivity of nanocrystalline CdS (nc-CdS) thin films is investigated. nc-CdS thin films grown on Si wafer by pulsed laser deposition followed by irradiation treatment were used to fabricate photo-sensors. Swift heavy ion irradiation (SHII) of the nc-CdS thin films was carried out using 70 MeV 58Ni6+ ions. The influence of irradiation fluence on the transport behaviour of nc-CdS is investigated by device performance under the illuminating light of wavelengths 355 nm, 405 nm and 470 nm. Indeed, the sensors presented here are easy to fabricate without requirement of rigorous synthesis procedure. Moreover, they illustrate characteristics similar to those of photo-sensors designed with complex structures and tedious procedures. The improvement in conductivity under the exposure of SHII is a consequence of enrichment in carrier concentration as reveals from current–voltage (I–V) measurements. The sensor exhibits improvements in the response time, responsivity, photosensitivity, quantum efficiency, and specific detectivity as a function of both the ion fluence and illuminating light wavelength. These sensors show superior value of all device parameters under the illumination wavelength 470 nm of visible light. The utmost values achieved for responsivity, sensitivity, external quantum efficiency, and specific detectivity are ∼ 82 A/W, 1.02 × 103 %, 19.5 × 103 %, and 5.05 × 1011 cm Hz1/2W−1 respectively under same illumination at 5 V for 1 × 1013 ions/cm2 irradiated photosensor. Under the same illumination, bias voltage and irradiation fluence the minimum value achieved for rise time and fall time is 183 ms and 61 ms respectively. A possible mechanism involved in both the SHII and illumination wavelength induced moderation of conductivity and consequently photosensitivity is explained on the basis of variation in the defect densities.

Sol-Gel Derived Cds Nanocrystalline Thin Films: Optical and Photoconduction Properties

Abstract High-quality CdS nanocrystalline thin films were grown by sol-gel spin coating method at different solution temperatures on glass substrates. As-deposited films exhibited nanocrystalline phase with hexagonal wurtzite structure and showed good adhesion and smooth surface morphology. It was clearly observed that the crystallinity of the thin films improved with the increase in solution temperature. Crystallites sizes of the films also increased and were found to be in the range of 10 mm to 17 nm. The influence of the growth mechanism on the band and sub-band gap absorption of the films was investigated using UV-Vis and photothermal deflection spectroscopy (PDS). The band gap values were calculated in the range of 2.52 eV to 2.75 eV. The band gap decreased up to 9 % with the increase in solution temperature from 45 °C to 75 °C. Absorption coefficients estimated by PDS signal showed the significant absorption in low photon energy region of 1.5 eV to 2.0 eV. The dark and illuminated I-V characteristics revealed that the films were highly photosensitive. The results demonstrated the potential applications of sol-gel grown CdS nanocrystalline thin films as photoconductors and optical switches.

Radiation stability of CBD grown nanocrystalline CdS films against ion beam irradiation for solar cell applications

Here we investigate the effect of swift heavy ion irradiation (SHII) on various properties of chemical bath deposited nanocrystalline CdS (nCdS) thin films. For this purpose, nCdS films are exposed to the varying ion fluences (1 × 1011–1 × 1014 ion/cm2) of 80 MeV O6+ ions. Glancing angle X-ray diffraction (GAXRD) and micro-Raman studies confirm almost negligible structural transformation in CdS after ion irradiation even at highest fluence i.e. 1 × 1014 ion/cm2. GAXRD, micro-Raman spectroscopy, field emission scanning electron microscopy and UV–Visible absorption spectroscopy studies suggest that the structure, shape and size of the particles as well as band gap of the nCdS films remain unaltered upon irradiation. The quality of the films and their radiation hardness is investigated by optical as well as electrical properties using photoluminescence spectroscopy and Hall measurements respectively. The films are found to be radiation resistant for 80 MeV O6+ ion irradiation as compared to other heavy radiations. The stability of various properties of nCdS films under the impact of SHII may be due to lesser or comparable value of electronic energy loss (Se) to the threshold value of Se. Radiation hardness of nCdS thin films is a good sign for fabrication of high performance, radiation stable and long lasting solar cell for extraterrestrial applications.

Effect of Deposition Time on the Characteristics of Nanocrystalline CdS Thin Films and Photodetection Properties

Effect of Deposition Time on the Characteristics of Nanocrystalline CdS Thin Films and Photodetection Properties

The semiconducting properties of CdS nanocrystalline thin films prepared by chemical bath deposition. Application to the eosin photodegradation

CdS nanocrystalline thin films were synthesized by chemical bath deposition for different deposition times (10–75 min) and the semiconducting and photo-electrochemical properties were investigated. The results indicate that the deposition rate decreases with the deposition time, due to the depletion of Cd2+ and S2− ions near the glass subtract. The structure is characterized by X-ray diffraction; the films crystallize in a cubic blende structure with (111) as a preferential orientation and the crystallite size varies between 13 and 35 nm. The surface morphology, studied by atomic force microscopy, indicates that the growth process occurs through ion by ion mechanism because of the stability of the complex Cd(NH3)4 (~7), the small deposition rate corroborates this result. The UV visible spectra of the films indicate a high transparency (80%). The transmittance data analysis give a variable forbidden band (2.2–2.4 eV), closely related to the deposition time and agree with the disorder range (230–500 meV). The capacitance–voltage measurement exhibits a linear behavior, characteristic of n type conduction, from which a flat band potential of −0.92 VSCE is determined. The Nyquist plot shows a semicircle assigned to the bulk contribution (=2.5 Ω cm2); the center is located below the real axis (−10°), ascribed to a constant phase element (CPE). A fill factor (FF) of 0.37 and energy conversion of 0.38% are obtained under visible illumination. As application, eosin solution (15 ppm) i oxidized under visible light; the best activity is obtained at pH ~6.3. 80% of eosin disappears after 1 h of exposition and the kinetic obeys to a first order model with a rate constant of 4.5 × 10−2 min−1.