Priyal Jain

Influence of grain size on the band-gap of annealed SnS thin films

Abstract Thin films of SnS were fabricated at room temperature on glass substrates by thermal evaporation. X-ray photo-electron spectroscopy confirmed that the films were stoichiometric in nature even after vacuum annealing. X-ray diffraction, Raman analysis and electron microscopy showed that the films were polycrystalline in nature with ortho-rhombic structure and preferred orientation. The only variation due to film thickness and annealing temperature was the grain size. Thus, this provided a chance to investigate the variation in optical properties as a function of the grain size. The energy band-gap and refractive index were estimated using UV-visible absorption spectra. The variation in band-gap with grain size showed blue-shift typical of electron quantum confinement. The effect of crystal ordering on refractive index was also evident by the linear increase of the refractive index with grain size.

Parameters influencing the optical properties of SnS thin films

Tin sulphide (SnS) thin films have been recognized as a potential candidate for solar cells. Many fabrication techniques have been used to grow SnS thin films. The band-gap, Eg of SnS films as reported in literature, were found to vary from 1.2–2.5 eV depending on the film fabrication technique. The present work reports the structural, compositional, morphological and optical characterization of SnS thin films fabricated by thermal evaporation at room temperature. Results show that for the given fabrication technique/condition, the band-gap functionally depends on the lattice parameter and grain size. The well-defined variation allows for tailoring SnS film as per requirements.

Localized surface plasmon resonance in SnS:Ag nano-composite films

Nano-composite films of Tin Sulfide (SnS) and silver fabricated by thermal evaporation showed two prominent peaks in the visible region of their extinction spectra. Theoretical modeling of the extinction spectra suggests that these two peaks (≈500 nm and ≈580 nm) correspond to the longitudinal mode and transverse mode surface plasmon resonance peaks arising from oblate silver nano-particles. Using grain size of silver and SnS obtained from structural and morphological characterizations of the samples and dielectric constants as per actuals, we have compared the experimental results with those from theory. The study shows that silver nano-particles efficiently scatters light and can be used for developing plasmonic based SnS solar cells with improved efficiencies.

Positron annihilation in p-[(p-ethoxybenzylidene) amino] benzonitrile (PEBAB)

Positron life-time measurements have been made in a positive dielectric anisotropy (ϵa > 0) liquid-crystal PEBAB as a function of temperature for the first time. It is found that unlike in negative dielectric anisotropy liquid-crystalline materials, the ortho-positronium life-time, τ2, increases as the order sets in: τ2 (isotropic liquid) < τ2 (nematic) < τ2 (solid) indicating that an increase in molecular ordering in this material brings about a decrease in the pick-off cross-section.

Photovoltaic performance of hybrid ITO/PEDOT:PSS/n-SnS/Al solar cell structure

The present paper discusses the performance of ITO/PEDOT:PSS/n-SnS/Al structured solar cells fabricated by thermal evaporation. The performance characterizing parameters such as the open circuit voltage, short circuit current density, series resistance, parallel resistance, ideality factor and the overall efficiency were found to be dependent on the SnS grain size in the nano-meter regime and incident light intensity. The experimental work directly reconfirms the theoretical results and ideas raised in the literature by early researchers.

Positron lifetimes in DL-norleucine and hexamethylbenzene

Abstract Positron lifetimes have been measured over a temperature range 22–125°C in DL-Norleucine and Hexamethylbenzene. The polymorphic phase transitions in these compounds are clearly reflected in the temperature dependence of the positron annihilation parameters. The changes in the longer lived lifetime component τ 2 and its intensity I 2 at the phase transitions could be explained on the basis of the free-volume model.

Positron annihilation studies in N-(p-hexyloxybenzylidene)-p′-toluidene (HBT)

Abstract Positron lifetime measurements have been carried out in the various phases of monotropic HBT as a function of temperature both in the absence and presence of a static magnetic field. The effect of quenching on the position lifetime in the various phases of HBT has also been investigated.