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Bismuth oxide (Bi2O3) nanoparticles are synthesized and evaluated for their function as materials for solar cells. Bi2O3 solution is inexpensively produced from the Nigella sativa seeds using a green synthetic method. The synthesized Bi2O3 solution is deposited by droplet casting method, and the synthesized nanofilm is dried at 80°C. Subsequently, diagnostic tests such as UV–VIS, XRD, and FTIR are performed on the Bi2O3/glass thin films. By means of the SEM, EDS, AFM, and I–V characteristics in dark and under illumination, the optical and structural characteristics of Bi2O3- nanoparticle films are investigated to determine the optical energy gap and crystalline material. X-ray diffraction reveals the presence of a tetragonal crystal system in the phase. The estimated band-gap energy Eg is approximately Eg1 = 3.6 eV, and FTIR analysis shows the degree of infrared absorption as a function of wavelength to demonstrate the presence of functional groups in bismuth-oxide molecules from Bi–O bonds. SEM–EDS morphology studies examine the occurrence of nanocrystals of various shapes and sizes. Finally, as a bulk heterojunction device, the I–V performance of the solar cell (Ag/Bi2O3/PSi/Si/Ag) deserves attention, and a fill factor FF= 48 is found for a solar-cell efficiency of 2.8%, ideality factor β= 1.35, characterization resistance RCH = 175 Ω, and the parallel resistance = 25.14 Ω·s. This cheap nanoparticle material could be an ideal candidate for future energy applications. [ABSTRACT FROM AUTHOR]

Dye-doped polymer films of Poly(methyl methacrylate) PMMA have been prepared with the use of the conventional solution cast technique. Natural dye has been extracted from environmentally friendly material of green tea (GT) leaves. Obvious Fourier transform infrared (FTIR) spectra for the GT extract were observed, showing absorption bands at 3401 cm-1, 1628 cm-1, and 1029 cm-1, corresponding to O-H/N-H, C=O, and C-O groups, respectively. The shift and decrease in the intensity of the FTIR bands in the doped PMMA sample have been investigated to confirm the complex formation between the GT dye and PMMA polymer. Different types of electronic transition could be seen in the absorption spectra of the dye-doped samples. For the PMMA sample incorporated with 28 mL of GT dye, distinguishable intense peak around 670 nm appeared, which opens new frontiers in the green chemistry field that are particularly suitable for laser technology and optoelectronic applications. The main result of this study showed that the doping of the PMMA polymer with green tea dye exhibited a strong absorption peak around 670 nm in the visible range. The absorption edge was found to be shifted towards the lower photon energy for the doped samples. Optical dielectric loss and Tauc's model were used to estimate the optical band gaps of the samples and to specify the transition types between the valence band (VB) and conduction band (CB), respectively. A small band gap of around 2.6 eV for the dye-doped PMMA films was observed. From the scientific and engineering viewpoints, this topic has been found to be very important and relevant. The amorphous nature of the doped samples was found and ascribed to the increase of Urbach energy. The Urbach energy has been correlated to the analysis of X-ray diffraction (XRD) to display the structure-properties relationships. [ABSTRACT FROM AUTHOR]

In this paper, the sample preparation of polymer nanocomposites based on methyl cellulose (MC) with small optical bandgaps has been discussed. Copper monosulfide (CuS) nanoparticles have been synthesized from the sodium sulphide (Na2S) and copper chloride (CuCl2) salts. Distinguishable localized surface resonance plasmon (LSRP) absorption peaks for CuS nanoparticles within the 680–1090 nm scanned wavelength range were observed for the samples. An absorption edge (Ed) was found to be widely shifted to a lower photon energy region. A linear relationship between the refractive index of the samples and the CuS fraction was utilized to describe the distribution of the particle. The optical bandgap of MC was reduced from 6.2 to 2.3 eV upon the incorporation of 0.08 M of CuS nanoparticles. The optical dielectric loss, as an alternative method, was used successfully to estimate the optical bandgap. Moreover, the electronic transition type was identified by using Tauc’s extrapolation method. The plots of the optical dielectric constant and energy bandgap as a function of the CuS concentration were utilized to examine the validity of the Penn model. For the nanocomposite samples, the Urbach energy was found to be increased, which can be evidence for a large possible number of bands-to-tail and tail-to-tail transitions. However, from the X-ray diffraction (XRD) analysis, it was also found that the synthesized CuS nanoparticles disrupted the crystallinity phase of the MC polymer. Finally, fourier transform infrared (FTIR) spectroscopy for the samples was also performed. Significant decreases of transmittance intensity as well as band shifting in the FTIR spectra were observed for the doped samples. [ABSTRACT FROM AUTHOR]

In this article we report the synthesis of CuS nanoparticle with distinguishable surface plasmonic resonance (SPR) peaks in near infrared region. For this purpose in situ synthesis (one-step fabrication) has been used to prepare CuS nanoparticles in PMMA polymer matrix at room temperature. The X-ray diffraction spectrum confirms the formation of CuS nanoparticles. The transmittance spectra of nano-composite samples reveal that the samples have a good transparency. The absorption spectra show a broad absorption peak in the wavelength region from 570 to 980 nm which is a characteristic SPR peak for CuS nanoparticle. An increase of refractive index was observed for the samples containing CuS nanoparticles. The linear relationship between the refractive index and volume fraction was observed. The appearance of SPR peak in refractive index spectra was attributed to CuS nanoparticles. Shifting of absorption edge to lower photon energy has been observed for nano-composite samples. The direct energy bandgap of nano-composite samples are reduced compare to pure PMMA polymer. The plot between the direct energy band gap and refractive index reveals that the decrease in bandgap energy is associated with the increase in index of refraction. The increase of optical dielectric constant can be ascribed to the formation of CuS nanoparticles. The low band gap of CuS nanoparticles in the present work reveals their importance for applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this paper composite materials, based on polymer blends of polyvinyl alcohol (PVA): polyvinyl pyrrolidone (PVP) with small optical band gap, has been studied. Silver sulfide (Ag 2 S) semiconductor particles have been synthesized in PVA:PVP blend host polymer, using in situ method. X-ray diffraction (XRD) analyses and Fourier transform infrared (FTIR) spectroscopy for the composite samples were carried out. From the XRD pattern, distinguishable crystalline peaks caused by the Ag 2 S semiconductor particles were observed. From the result of FTIR spectroscopy, the intensity of the FTIR bands were shifted and increased, revealing the occurrence of interactions between the PVA:PVP blend system and Ag 2 S particles. The composite samples were found to exhibit absorption spectra that cover UV–visible to near infrared regions. The absorption edge was found to be 5 eV for pure PVA:PVP system and shifted to 1.15 eV for incorporated PVA:PVP with 3 M of Ag 2 S. The refractive index was also evaluated for the samples and observed to be increased from 1.15 to 1.52 as doping increased to the highest. A linear relationship between the refractive index and the filler fraction has been reported. Theoretical discussion of optical dielectric loss, which is a crucial parameter for the band gap estimation, was given. The achieved results reveal that spectra of the optical dielectric loss (ɛ i ) can be used to study the band gap structure and Tauc's model can be important in determining the types of electronic transition. The optical band gap was found to decrease from 5.2 eV for the pure PVA:PVP to 1.1 eV for doped PVA:PVP with 3 M of Ag 2 S. Such reduction can be associated with the increase of optical dielectric constant. Finally, the correlation between optical dielectric constant and density of states was discussed. [ABSTRACT FROM AUTHOR]