H. Algarni

An investigation on the key features of a D–π–A type novel chalcone derivative for opto-electronic applications

The current study is focused on the donor–bridge–acceptor (D–π–A) type of novel organic charge transport and non-linear optical material, 1-(4-bromophenyl)-3-(2,4,5-trimethoxyphenyl) prop-2-en-1-one (2,4,5-TMBC) to spotlight its various important properties through experimental and quantum chemical approaches. The compound 2,4,5-TMBC was synthesized via a Claisen–Schmidt condensation reaction and its single crystal was grown by a slow evaporation solution growth technique. FT-IR and FT-Raman spectra of 2,4,5-TMBC were obtained and investigated. The molecular geometry of 2,4,5-TMBC was optimized by HF, B3LYP, CAM-B3LYP, wb97xd and LC-BLYP methods using the 6-31G* basis set. The calculated geometrical parameters and vibrational spectra are in good agreement with the experimental results. Time dependent density functional theory (TD-DFT) has been applied to investigate the optical properties of the title compound. The absorption wavelength calculated at the TD-B3LYP/6-31G* level of theory in the gas phase was in good agreement with the experimental value (∼400 nm) when compared with other methods. The HOMO–LUMO energy gap was calculated at all the applied levels of theory. The total dipole moment, polarizability, anisotropy of polarizability and static first and total hyperpolarizability values of 2,4,5-TMBC were calculated at different levels of theory. The dipole moment and first hyperpolarizability values are found to be many folds (2 and 56 times calculated at B3LYP) higher than urea. It is also expected that 2,4,5-TMBC would be electron transport material due to its smaller electron reorganization energy value. The study of non-linear optical (NLO) properties shows that 2,4,5-TMBC would be an outstanding candidate for NLO device applications.

Highly porous ZnO nanosheets self-assembled in rosette-like morphologies for dye-sensitized solar cell application

This paper reports a facile low temperature hydrothermal process to grow highly porous ZnO nanosheets, self-assembled in rosette-like morphology, over the transparent indium tin oxide (ITO) glass substrate for dye-sensitized solar cell application. The prepared porous nanosheets were examined in detail using several techniques to understand the morphological, structural, compositional, optical and photovoltaic properties. The detailed morphological investigations reveal that the prepared nanosheets are made by the accumulation of small ZnO nanoparticles with typical diameters of 28 ± 3 nm. A systematic growth process to prepare such ZnO nanosheets is also discussed in terms of chemical reactions involved. The prepared nanosheets possess the stoichiometric elemental ratios of Zn and oxygen and exhibiting good crystallinity and wurtzite hexagonal phase along with good optical properties. Furthermore, the prepared ZnO nanosheets on ITO substrates were directly utilized as a photo-anode to fabricate an efficient dye-sensitized solar cell (DSSC), which demonstrated a reasonable light-to-electricity conversion efficiency of ∼3.4% with high short circuit current (JSC) of 9.45 mA cm−2, open circuit voltage (VOC) of 0.654 and fill factor of 0.55. The obtained JSC and the performance of the fabricated DSSC are attributed to the high surface to volume ratio of porous ZnO nanosheets, which delivers the high light harvesting efficiency.

Ag-Doped ZnO Nanoparticles for Enhanced Ethanol Gas Sensing Application

Herein, we report the synthesis, characterization and ethanol gas sensing application of Ag-doped ZnO nanoparticles. The nanoparticles were synthesized through a facile hydrothermal process and characterized through various characterization techniques. The detailed characterizations confirmed that the synthesized Ag-doped ZnO nanoparticles are grown in high density with an average diameter of ~20 ± 5 nm, possessing well-crystalline wurtzite hexagonal crystal structure and exhibiting good optical properties. The as-synthesized Ag-doped ZnO nanoparticles were further used as functional material to fabricate efficient ethanol gas sensor which exhibited excellent gas response. The detailed gas sensing experiments revealed that at an optimized temperature, i.e., 320 °C, the recorded gas response was 32.815 for 200 ppm concentration of ethanol gas. Finally, a plausible gas sensing mechanism was also presented in this paper.

Pseudopotential calculations of AlSb under pressure

The dependence on hydrostatic pressure of the electronic and optical properties of zinc-blende AlSb semiconducting material in the pressure range of 0-20kbar has been reported using a pseudopotential approach. At zero pressure, our findings showed that the electron and heavy hole effective masses are 0.11 and 0.38m0, respectively. Moreover, our results yielded values of 3.3289 and 11.08 for refractive index and high frequency dielectric constant, respectively. These results are found to be in good accord with experiment. Upon compression, all physical parameters of interest showed a monotonic behavior. The pressure-induced energy shifts for the optical transition related to band-gaps indicated that AlSb remains an indirect (Г-X) band-gap semiconductor at pressures from 0 to 20kbar. The trend in all features of interest versus pressure has been presented and discussed. It is found that the lattice parameter is reduced from 0.61355 to 0.60705nm when pressure is raised from 0 to 20kbar. The present investigation may be useful for mid-infrared lasers applications, detectors and communication devices.

Rare earth Eu 3+ co-doped AZO thin films prepared by nebulizer spray pyrolysis technique for optoelectronics

AbstractRare earth element (i.e.) europium co-doped aluminum zinc oxide (Eu:AZO) thin films were deposited on microscope glass slides by nebulizer spray pyrolysis with different Eu-doping concentrations (0, 0.5, 1, and 1.5%). The deposited films were investigated using X-ray diffraction, AFM, EDAX, FT-Raman, UV–visible, PL, and Hall effect measurements. X-ray confirmed the incorporation of aluminum and europium ions into the ZnO structure. All films have polycrystalline nature with hexagonal wurtzite structure at (002) direction. Topological depictions exhibited minimum surface roughness and low film thickness for pristine AZO thin film. EDAX study authorizes the existence of Zn, O, Al, and Eu in Eu: AZO thin films. Raman spectra exhibited the characteristic of ZnO-wurtzite structure (E2-high) mode at 447 cm−1. The deposited film showed high optical transmittance of ~90% in visible region, and the direct energy gap was around 3.30 eV for pristine AZO thin film. The PL spectra emitted a powerful UV emission situated at 388 nm, and it indicates that the film has good optical quality. The obtained large carrier concentration and less resistivity values are 4.42 × 1021 cm−3 and 3.95 × 10−4 Ω cm, respectively, for 1.5% Eu-doped AZO thin film. The calculated figure of merit value is 17.29 × 10−3 (Ω/sq)−1, which is more suitable for the optoelectronic device.

Energy gaps, valence and conduction charge densities and optical properties of GaAs1−xPx

The electronic structure and its derived valence and conduction charge distributions along with the optical properties of zinc-blende GaAs1−xPx ternary alloys have been studied. The calculations are performed using a pseudopotential approach under the virtual crystal approximation (VCA) which takes into account the compositional disorder effect. Our findings are found to be generally in good accord with experiment. The composition dependence of direct and indirect bandgaps showed a clear bandgap bowing. The nature of the gap is found to depend on phosphorous content. The bonding and ionicity of the material of interest have been examined in terms of the anti-symmetric gap and charge densities. The variation in the optical constants versus phosphorous concentration has been discussed. The present investigation may give a useful applications in infrared and visible spectrum light emitters.

Bulk growth, structural, vibrational, crystalline perfection, optical and dielectric properties of L-threonine doped KDP single crystals grown by Sankaranarayanan-Ramasamy (SR) method

In the present work, the authors have grown the bulk-sized single crystals of pure (Size ~ 45 × 10 × 10 mm3) and first time L-threonine (LT)-doped (Size ~ 85 × 10 × 8 mm3) KDP with high quality by Sankaranarayana-Ramasamy (SR) method in an aqueous solution at constant temperature. A remarkable enhancement in the growth rate was observed from 3.2 mm/day (pure) to 6 mm/day (LT doped), respectively. The crystal structure, lattice parameters and growth direction were confirmed by powder X-ray diffraction analysis. FT-IR study confirms the presence of L-Threonine doping in KDP. Further, the vibrational modes and surface morphology was studied by FT-Raman spectroscopy along with etching treatment and shows remarkable reduction of surface defects. The optical transparency of SR-grown KDP crystals was found to be enhanced from 76 to 88% due to LT doping. The optical band gap was calculated for both the crystals and found to be 5.68 and 5.53 eV. Crystalline perfection of the grown crystals was assessed by high-resolution X-ray diffraction, dielectric and wet chemical etching studies and found to be good. The obtained result shows that the grown crystals can be used for laser applications.