In the cutting-edge world, semiconductor metal oxides usually tend to have a high optical band gap (>3.0 eV), significantly acceptable for potential optoelectronic applications. The present study discusses the synthesize of pristine tungsten trioxide (WO3) and Silver (Ag) doped WO3 (Ag: WO3) thin films onto a glass substrate at 450 °C, with varying concentrations of Ag doping (2, 4, 6, 8 and 10 at.%) using a simple Spray Pyrolysis Technique. Field emission scanning electron microscopy (FESEM) analysis showed the presence of particles in the WO3 and Ag: WO3 materials. The X-ray diffraction (XRD) pattern confirmed that the samples' hexagonal structure remained intact. In addition, Rietveld refinement was used for the samples to study the crystal structure meticulously. Because of the surface plasmon resonance effect, the samples' distinguishing characteristics were visible in their optical nature. For pristine WO3, the experimental band gap was determined to be 3.20 eV, and for varying doping concentrations, it was found to be 3.15 eV-2.90 eV, respectively. Furthermore, the fracture has remained imperceptible at elevated concentrations, resulting in a substantial influence on the optical characteristics of 10% Ag: WO3 thin films. The estimated redox potential for 2% Ag: WO3 shows a considerable influence of the band edge potential of the Conduction Band (CB) and Valance Band (VB). The activation energy was determined using temperature-dependent electrical resistivity and exhibited an ohmic nature. The synthesized material exhibited a negative temperature coefficient (NTC) effect at higher concentrations of doping, suggesting its potential applicability as a thermistor. A comprehensive analysis of this present study indicates that Ag can be a viable candidate for doping on WO3 thin films for use in optoelectronic devices.
A simple and inexpensive spray pyrolysis deposition (SPD) approach was used to produce TiO2 and Cr (2-8) at.%-doped TiO2 thin films. To explore the morphological features of the films, FE-SEM micrographs were used and found that 6 and 8 at.% TiO2:Cr films had fibrous patterns with diameters of 0.45 and 0.78 µm, respectively, while the remainder of the films were agglomerated particles. From X-ray diffraction investigation, it was found that the TiO2 thin films had an anatase crystal phase (tetragonal) up to 6 at.% Cr doping, while an anatase-rutile mixed crystalline phase was identified for 8 at.% Cr doping. The crystallite size of the pristine TiO2 film was 35 nm, while for TiO2:Cr films, it ranges from 35 to 46 nm. The Fizeau fringes technique was employed to measure the thickness of the TiO2 film and 165 nm was found for pristine TiO2 and 164-180 nm for TiO2:Cr films. UV-visible spectroscopy was used to study optical properties such as absorbance, refractive index, optical band gap, dielectric constant, and optical conductivity. As the Cr concentration increases, the optical band gap decreases from 3.40 eV to 2.70 eV. Using the four-point probe method, it was found that the resistivity changes with temperature and is also affected by the Cr content.
A novel semi-organic crystal has been grown using slow evaporation technique by doping organic compound L-asparagine monohydrate (C4H8N2O3·H2O) with inorganic material Magnesium sulphate heptahydrate (MgSO4·7H2O). The crystallographic parameters like strain, dislocation density and crystallite size were calculated by powder X-ray diffraction method. Functional groups were identified and bond length, force constants were calculated from FT-IR spectroscopy. Energy dispersive X-ray (EDX) analysis was used to identify the constituent elements of the crystal. Kinetic and thermodynamic parameters, such as, activation energy Ea, change in Gibb's free energy (ΔG) and change in enthalpy (ΔH) have been determined by thermogravimetric analysis (TGA) analysis. Ea, ΔH and ΔG show positive values and change in entropy (ΔS) shows negative ones. The thermal degradation behavior of the crystals has been analyzed by differential scanning calorimetry (DSC) analysis. Various optical constants such as optical band gap, lattice dielectric constant, absorbance, extinction coefficient, the ratio of free charge carrier concentration to the effective mass, Urbach energy, optical and electrical conductivities were estimated from UV-vis transmittance data. High optical conductivity (1010 s-1) justifies the good photo response nature of the semi-organic crystal.
In the present study, we propose a novel type of lead-free double halide perovskite Cs2AgAsCl6 material exhibiting exceptional photovoltaic and photocatalytic properties. Density functional theory (DFT) is employed to investigate the photovoltaic and photocatalytic properties based on several significant properties of the Cs2AgAsCl6 material. The thermodynamic stability of Cs2AgAsCl6 has been confirmed by the enthalpy formation, which is -32.36 eV f.u.-1 Dispersion of phonons near the gamma point confirmed the existence of dynamical stability. The constant value of the heat capacity is 59.45 cal per cell K, which is calculated by the Dulong-Petit limit. The GGA-PBE and HSE-06 functional approaches determined indirect bandgaps of 1.31 and 2.49 eV, respectively, for a semiconductor whose electronic properties revealed photocatalytic efficiency. The effective masses of an electron and a hole are 0.46 me and 0.61 me, respectively, which may enhance the photocatalytic dye degradation owing to their low carrier effective mass. Notably, better photocatalytic properties, i.e., dye degradation, are confirmed by the redox potential. The estimated edge potentials of the conduction band (CB) and valence band (VB) are -0.048 and 2.448 eV, respectively, which are greater than the H+/H2 and O2/H2O potentials. The Cs2AgAsCl6 material reveals an outstanding optical property that is suitable for photovoltaic applications. Therefore, Cs2AgAsCl6 can act as a potential candidate in the field of photovoltaic and photocatalytic applications.
Double halide perovskites (A2M+M3 +X6) have been considered as high-performance material for optoelectronic and photovoltaic devices. Here, we investigate the structural, thermodynamic, optical, mechanical and electronic properties of pressure-induced Cs2AgBiCl6 samples. The phase stability is confirmed by the tolerance and octahedral factor calculations. The thermodynamic potentials such as enthalpy, free energy, entropy, and heat capacity are observed in the phonon modes. The indirect to direct band gap is observed due to disorders of Ag+/Bi3+ cations in their sub-lattice. In this study, the induced pressure was varied between 0 and 80 GPa and the transition of the band gap energy from semiconductor to metal was observed at a hydrostatic pressure of 80 GPa. The bond length in between Ag and Bi atoms is reduced due to crystal defect, occurred under induced pressure. The narrow band gap energy and the partial density of states of the disordered Cs2AgBiCl6 samples refer to the relocation of charge carriers to facilitate the photocatalytic reaction. As the pressure changes, the absorbing edge also moves into the lower energy region. The pressure-inducted Cs2AgBiCl6 sample has a strong absorption in the range of visible wavelength of light and shifted in the ultraviolet region. Simultaneously, the pressure-driven material extend the symmetry breaking of [AgBi]-6 and [AgCl]-6 octahedra and hence the total energy decreased due to narrow band gap energy. Phase-change dihalide materials have excellent properties, opening up new avenues for device applications. The mechanical properties suggest that the pure and pressure-inducted Cs2AgBiCl6 samples have potential characteristics for an optoelectronic and photovoltaic applications.
Non-toxic lead free inorganic metal halide cubic double perovskites have drawn a lot of attention for their commercial use in optoelectronic and photovoltaic devices. Here we have explored the structural, electronic, optical and mechanical properties of lead-free non-toxic inorganic metallic halide cubic double perovskite Cs2AgBiBr6 in its ordered and disordered forms using first-principles density functional theory (DFT) to verify the suitability of its photovoltaic and optoelectronic applications. The indirect bandgap of Cs2AgBiBr6 is tuned to a direct bandgap by changing it from an ordered to disordered system following the disordering of Ag+/Bi3+ cations by creating antisite defects in its sublattice. In the disordered Cs2AgBiBr6, the Bi 6p orbital modifies the conduction band significantly and leads to a shift the conduction band minimum (CBM) from L to Γ-point. Consequently, the system changes from indirect to direct band gap material. At the same time the band gap reduces significantly. The band gap of Cs2AgBiBr6 decreases from 2.04 eV to 1.59 eV. The absorption edge towards the lower energy region and strong optical absorption in the visible to the UV region indicate that the disordered direct band gap material Cs2AgBiBr6 is appropriate for use in solar cells and optoelectronic and energy harvesting devices. Dielectric function, reflectivity and refractive index of disordered direct band gap material Cs2AgBiBr6 is favorable for its optoelectronic and photovoltaic applications. However, its stability and ductility favor its thin film fabrication. The creation of antisite defects in the sublattice of double perovskites opens a new avenue for the design of photovoltaic and optoelectronic materials.
The antiperovskites based on metal halides have emerged as potential materials for advanced photovoltaic and electronic device applications. But the wide bandgap of non-toxic CsSnCl3 reduces its photovoltaic efficiency. Here, we report the change of electronic structure of CsSnCl3 at different pressure by using GGA-rPBE and GGA-PBEsol functionals and the GW method. We have shown that the prediction of electronic structure transition (semiconducting to metallic state) strongly depends on the exchange-correlation and the GW method gives the most reasonable values of the bandgap under pressure. The pressure increases the electronic density of states close to the Fermi level by pushing the valence electrons upward and thus, reduces the bandgap linearly. Afterward, we have also investigated the influence of pressure on absorption coefficient, and mechanical properties meticulously. Although the pressure shifts the absorption peak to lower photon energies, the absorption coefficient is slightly improved.
Inorganic double halide perovskites have a wide range of applications in low-cost photovoltaic and optoelectronic devices. In this manuscript, we have studied their structural, electronic, mechanical and optical properties using density functional theory (DFT) simulations. In this work, hydrostatic pressure is induced from 0 to 50 GPa. Disordered Ag and Bi atoms have a large impact on band gap energy; in this case, the indirect band gap is transferred towards a direct band gap. We have seen that pressure-driven samples have transformed a band energy semiconductor into a metallic one. Under the induced hydrostatic pressure, the covalent bond is transformed into a metallic bond and the bond lengths are reduced. Meanwhile, pressure-induced samples enhance symmetry breaking in [AgBr6]5- and [BiBr6]3- octahedra, which reduces the density of states of the Fermi surface and lowers the total energy. The mechanical behaviors demonstrated that the studied materials are mechanically stable as well as ductile and their ductile nature is enhanced by the driving pressure. The absorption peak is shifted towards the low energy region with increased hydrostatic pressure. The absorptivity and dielectric constant values are also increased with driving pressure. Phase transformed double halide perovskites triggered by outside stimuli produce several outstanding materials properties, giving great scope for a broad range of applications. This type of pristine and disordered double halide perovskite with pressure-driven semiconductor-to-metal phase transition samples may have potential applications in optoelectronic and photovoltaic devices.
In this work, a simple, co-precipitation technique was used to prepare un-doped, pure tin oxide (SnO2). As synthesized SnO2 nanoparticles were doped with Cu2+ ions. Detailed characterization was carried out to observe the crystalline phase, morphological features and chemical constituents with opto-electrical and magnetic properties of the synthesized nanoparticles (NPs). X-ray diffraction analysis showed the existence of crystalline, tetragonal structure of SnO2. Both the sample synthesized here showed different crystalline morphology. The band gap energy (Eg) of the synthesized sample was estimated and it was found to decrease from 3.60 to 3.26 eV. The band gap energy reduced due to increase in Cu2+ dopant amount inside the SnO2 lattice. Optical properties were analyzed using absorption spectra and Photoluminescence (PL) spectra. It was observed that Cu2+ ions incorporated SnO2 NPs exhibited more degradation efficiencies for Rhodamine B (RhB) dye compared to un-doped sample under UV-Visible irradiation. The dielectric characteristics of un-doped, pure and Cu2+ incorporated SnO2 nanoparticles were studied at different frequency region under different temperatures. The ac conductivity and impedance analysis of pure and Cu2+ incorporated SnO2 nanoparticles was also studied. The magnetic properties of the synthesized samples were analysed. Both the sample showed ferromagnetic properties. The research indicated that the Cu2+ ions doping can make the sample a promising candidate for using in the field of optoelectronics, magneto electronics, and microwave devices.
The title compound, C16H16FNO3, exists in a trans configuration with respect to the C=N bond [1.258â (2)â Å]. The central meth-oxy O atom deviates from the plane of the attached benzene ring by 0.0911â (14)â Å. The dihedral angle between the aromatic rings is 47.58â (11)°. The crystal structure features C-Hâ¯N and C-Hâ¯O inter-actions.
In the title salt, C16H18NO(+)·C10H7O3S(-), the substituents attached to the central C=C bond adopt a trans conformation and the benzene and pyridinium rings are nearly coplanar, making a dihedral angle of 6.01â (9)°. The crystal structure features weak C-Hâ¯O hydrogen bonds and C-Hâ¯π inter-actions .
The mol-ecules of the title compound, C16H18N2, exists in a trans conformation with respect to the C=N bond [1.270â (3)â Å]. The least-squares plane of the di-methyl-amino group makes a dihedral angle of 1.3â (2)° with the ring to which it is attached. The dihedral angle between the two aromatic rings is 11.70â (2)°. The crystal structure features weak C-Hâ¯π inter-actions.
In the title mol-ecular salt, C16H10NO(+)·I(-), the dihedral angle between the pyridinium and benzene rings is 6.61â (8)°. In the crystal, the cation is linked to the anion by a C-Hâ¯I inter-action arising from the activated aromatic C atom adjacent to the N(+) cation.
