Determination of optical bandgap energy and optical characteristics of Cd30Se50S20 thin film at various thicknesses

Qasem, Ammar; Mostafa, Mohamed S.; Yakout, H.A.; Mahmoud, Mona; Shaaban, E.R.

doi:10.1016/j.optlastec.2021.107770

Cited by 38 publications

(16 citation statements)

References 72 publications

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“…The thickness estimates are slightly dispersed around their original values for films with d > 1.5 μm . At higher film thickness, the optical constants exhibit a nonlinear dependence commonly observed in earlier research findings [ 49 ]. In Fig 3(b) , n and k estimates exactly match with the original profiles throughout, however, in Figs 3(d) , 4(b) and 4(d) , there exist slight differences between the original and estimated n , k profiles especially in the low-wavelength regime partially including ultraviolet-visible spectral range.…”

Section: Resultssupporting

confidence: 65%

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Extracting film thickness and optical constants from spectrophotometric data by evolutionary optimization

et al. 2022

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In this paper, we propose a simple and elegant method to extract the thickness and the optical constants of various films from the reflectance and transmittance spectra in the wavelength range of 350 − 1000 nm. The underlying inverse problem is posed here as an optimization problem. To find unique solutions to this problem, we adopt an evolutionary optimization approach that drives a population of candidate solutions towards the global optimum. An ensemble of Tauc-Lorentz Oscillators (TLOs) and an ensemble of Gaussian Oscillators (GOs), are leveraged to compute the reflectance and transmittance spectra for different candidate thickness values and refractive index profiles. This model-based optimization is solved using two efficient evolutionary algorithms (EAs), namely genetic algorithm (GA) and covariance matrix adaptation evolution strategy (CMAES), such that the resulting spectra simultaneously fit all the given data points in the admissible wavelength range. Numerical results validate the effectiveness of the proposed approach in estimating the optical parameters of interest.

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Section: Resultssupporting

confidence: 65%

Section: Analysis and Discussionsupporting

confidence: 68%

Extracting film thickness and optical constants from spectrophotometric data by evolutionary optimization

et al. 2022

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“…The vertical excitation energy from the ground state to the first dipole-allowed excited state corresponds to the optical energy gap, which is the lowest energy transition identified in the experimental absorption spectra [ 42 ]. We have estimated the optical band gap (E opt ) from the variation in (

) vs. photon energy ( h

) via the Tauc formula [ 43 , 44 ];

where k is a constant. The direct E dir and indirect E ind band gap for allowed transitions are represented by two values: x = 2 and x = 0.5, respectively.…”

Section: Resultsmentioning

confidence: 99%

Structural and Optical Characterization of g-C3N4 Nanosheet Integrated PVC/PVP Polymer Nanocomposites

Alshammari

et al. 2023

Polymers

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The present work considers the integration of g-C3N4 nanosheets into PVC/PVP polymer nanocomposites at ratios of 0.0, 0.3, 0.6, and 1.0 wt%. The XRD data scans showed semicrystalline structures for all PVC/PVP/g-C3N4 polymer blend films. The FTIR and Raman measurements revealed intermolecular hydrogen bonding between the g-C3N4 surface and the OH− groups of the PVC/PVP network. ESEM morphology analysis for PVC/PVP/g-C3N4 nanocomposite films displayed homogeneous surface textures. The data of TGA showed improved thermal stability as the decomposition temperature increased from 262 to 276 °C with the content of g-C3N4 (0.0–1.0 wt%). The optical absorbance data for PVC/PVP films improved after the addition of g-C3N4. The optical energy gaps showed compositional dependence on the g-C3N4 content, which changed from 5.23 to 5.34 eV at indirect allowed transitions. The refractive index for these blend films enhanced (1.83–3.96) with the inclusion of g-C3N4. Moreover, the optical susceptibility for these nanocomposite films increased as the content of g-C3N4 changed from 0.0 to 1.0 wt%. Finally, the values of the nonlinear refractive index showed improvement with the increased percentage of g-C3N4. When g-C3N4 was added up to 1.0 wt%, the DC conductivity improved from 4.21 × 10−8 to 1.78 x 10−6 S/cm. The outcomes of this study prove the suitable application of PVC/PVP/g-C3N4 in optoelectronic fiber sensors.

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“…11 shows the relationship between α and hν for CdS/glass films with extraordinary CdS layer thickness. As well, the absorption behavior increases as the thickness of the CdS layer increases, especially in the UV range [47]. In addition, the non-zero value of light absorption observed at energies less than the original absorption edge is owing to light absorption at the grain boundaries [48,49].…”

Section: Optical Propertiesmentioning

confidence: 96%

Studying the structural, optical spectroscopic ellipsometry and electrical properties of variable-CdS thickness/CdTe for solar cell applications

Sebak¹,

Ghalab²,

El-Taher³

et al. 2022

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"The structural and optical properties of CdS window layer at different thicknesses in the range of (100-300 nm) deposited on pre-cleaned glass substrates (CdS/glasses) via the thermal evaporation process are studied in the current work. The structural analysis is done using Rietveld refinement and atomic pressure microscope techniques. The films of CdS/glass showcase a wurtzite behavior. XRD and AFM tests are confirmed that the structural parameters improve as the thickness of the CdS-layer increases. The optical constants (the refractive index n, the extinction coefficient, k and the bandgap energy values are estimated from spectroscopic ellipsometry (SE) via the construction of an optical model. The refractive index of the CdS/glass films increases with the increase of CdS-layer thickness. This, in turn, is due to the rise of the size of the crystal in the thin layers. It is also found that as the thickness of the CdS-layer rises, so does the overall behavior of the extinction coefficient. Additionally, the bandgap energy of the direct transition decreases from 2.45 eV (d=100 nm) to 2.25 eV (d=300 nm). The dark and illumination I-V photovoltaic characteristics of fabricated devices are explored by depositing a p-CdTe thin layer (500 nm) over varying thicknesses of CdS thin films (100- 300 nm) prepared on glass substrates (2 mm) and thus, the Ni/n-CdS/i-AgSe/p-CdTe/Pt heterojunction has been successfully fabricated with an AgSe buffer layer deposited directly on the p-CdTe absorber laryer. The n-CdS window layer is deposited on i-AgSe buffer layer. In dark conditions, based on the dependence of the forward and reverse current-voltage, the essential behavior related to the fabricated diode has been determined. As well, in the illumination case, the open-circuit voltage, the short-circuit current, the fill factor, the power conversion efficiency, (PCE), photoresponsivity, quantum efficiency, dependence of generated photocurrent on the light intensity, dependence of the generated photocurrent on wavelength (λ)for the studied solar cell are computed and discussed."

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Determination of optical bandgap energy and optical characteristics of Cd30Se50S20 thin film at various thicknesses

Cited by 38 publications

References 72 publications

Extracting film thickness and optical constants from spectrophotometric data by evolutionary optimization

Extracting film thickness and optical constants from spectrophotometric data by evolutionary optimization

Structural and Optical Characterization of g-C3N4 Nanosheet Integrated PVC/PVP Polymer Nanocomposites

Studying the structural, optical spectroscopic ellipsometry and electrical properties of variable-CdS thickness/CdTe for solar cell applications

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