R.M. Mehra

Structural, Transport and Optical Properties of Boron-doped Zinc Oxide nanocrystalline

The paper has reported the structural, transport and optical properties of boron doped zinc oxide (ZnO:B) thin films grown on glass substrate by sol-gel spin coating process. It is observed from the analysis of the X-ray diffraction (XRD) results that the crystalline quality of the films is improved with increasing B concentration. A crystallite size of ∼17 nm is obtained for B doped films. A minimum resistivity of 7.9×l0 −4 Ω·cm is obtained at 0.6 at.% of B concentration in the ZnO:B films. Ionized and intragrain cluster scattering are found to dominate the scattering mechanism in ZnO:B films. Optical interference pattern in transmittance spectra shows good homogeneity with a transparency of ∼88% in the visible region. The band gap of the films is increased from 3.24 to 3.35 eV with increasing B concentration. Band gap widening is analyzed in terms of Burstein–Moss shift. The origin of the broad band photoluminescence (PL) spectra is explained in terms of the intragrain cluster scattering.

ZnO based quantum dot sensitized solar cell using CdS quantum dots

This paper reports the fabrication of Zinc Oxide (ZnO) based quantum dot sensitized solar cell using Cadmium Sulphide (CdS) quantum dots (QDs) capped by poly vinyl alcohol (PVA). Chemical route was used to synthesize ZnO nanoparticles (NPs) as well as CdS QDs. The crystallite size of ZnO NPs was obtained to be 28 nm at 7 pH. The size of QDs decreased from 5.6 to 2.6 nm with increase in the PVA concentration from 2 to 10 wt. %. There is a blue shift in the band gap of QDs with increase in the concentration of PVA. Current-Voltage characteristic of the cell was obtained and various solar cell parameters were estimated. The efficiency of quantum dot sensitized solar cells was found to be 1.3% at AM 1.5.

Effect of Surface Roughness on Laser Induced Nonlinear Optical Properties of Annealed ZnO Thin Films

Variation of nonlinear optical properties with surface roughness of ZnO thin films deposited on corning glass substrates at different annealing temperature (TA) was reported. The films were characterized by X-ray diffraction (XRD), UV-Vis-NIR transmission and single beam z -scan technique using second harmonics of Nd: YAG laser. Surface morphology of the samples was investigated by atomic force microscopy (AFM). Surface roughness was found minimum (8.4 nm) for ZnO sample annealed at 450 °C. The nonlinear optical properties (NLO) were found to be dependent on surface roughness and the highest value of third order nonlinear susceptibility (χ (3) =4.3×10 −7 esu) was obtained for ZnO at TA 450 °C.

Quantum Dot Sensitized Solar Cells (QDSSCs)

Quantum Dot Sensitized Solar Cells (QDSSCs) are currently a field of intense research across the globe as they provide a promising cost-effective alternative for efficient energy conversion. The wide acceptance of QDs is due to their exceptional optical properties, size-tunable electro- and photoluminescence, multiple exciton generation (MEG), and broad absorption spectra. However, the progress of QDSSCs is confronted with many challenges. The basic strategies of enhanced photovoltaic characteristics depend on factors like—suppressed charge carrier recombination at the interfaces, improved photon absorption, and construction of tandem structures. Exploiting further nanoscience and nanotechnology will be essential in overcoming these hurdles for achieving better functional quantum dot sensitized solar cells. The current research work focuses on how the prevalent challenges are being overcome in order to develop efficient functioning QDSSC.

Electrical, thermal, and dielectric studies of ionic liquid-based polymer electrolyte for photoelectrochemical device

In this work, solution cast method was adapted for the preparation of 1-ethyl-3-methylimidazolium dicyanamide (EMImDCN)-doped solid polymer electrolyte. Optimum composition of polymer electrolyte (polyethylene oxide + sodium iodide) was treated as the host polymer. The ionic conductivity was further enhanced by adding low-viscosity ionic liquid (IL) EMImDCN. Electrical, thermal, dielectric, and photoelectrochemical properties of polymer host and IL-doped solid polymer electrolyte (ILDPE) are presented in detail. An electrochemical device, that is, dye-sensitized solar cell was fabricated using maximum conducting ILDPE film, which shows short-circuit current density of 0.118 mA/cm2, open-circuit voltage of 0.71 V, and overall efficiency of 0.061% at 1 sun condition.