EFFECT OF GAMMA IRRADIATION ON CdTe/ZnTe BILAYER THIN FILMS

In the present investigation, CdTe/ZnTe bilayer thin films were deposited by vacuum evaporation technique followed by vacuum annealing. The individual layer thickness in CdTe/ZnTe bilayer was varied in different ratios. These bilayer thin films were subjected to 100 KGy doses of 60Co gamma (γ) rays. The morphological studies were carried out by Scanning Electron Microscopy (SEM). The SEM micrographs suggested that γ-irradiation induces surface modifications. The elemental composition was studied by Energy Dispersive X-ray Spectroscopy (EDAX). EDAX studies indicated no compositional changes after γ- irradiation. The optical constants of γ-irradiated films were estimated on the basis of optical absorption spectra obtained from UV-vis-spectrophotometer. The Photoluminescence (PL) spectroscopy was carried out for defect studies. PL-studies indicated that the γ- irradiation results in defect annihilation. Support from the Faculty exchange program between the University of West Georgia, USA and the Birla College, Kalyan, India is acknowledged

Formation of nanocrystalline TiO<SUB>2</SUB> by 100MeV Au<SUP>8+</SUP>

Nanocrystalline TiO<SUB>2</SUB> structures are formed by irradiation of 100 MeV Au<SUP>8+</SUP> ion beam on amorphous thin films of TiO<SUB>2</SUB>. Surface morphology of the nanocrystals is studied by Atomic Force Microscopy (AFM). Amorphous to nanocrystalline phase transformation is identified by Glancing Angle X-ray Diffraction (GAXRD) and Raman spectroscopic studies. Optical characterization is carried out by UV–VIS spectroscopy technique. Blue shift observed in absorption band edge indicates the formation of nanophase TiO<SUB>2</SUB> after irradiation. The impinging swift heavy ion (100 MeV Au<SUP>8+</SUP>) induces nucleation of nanoparticles along the ion trajectory through inelastic collisions of the projectile with electrons of the material. It is observed that the shape and size of nanoparticles formed is dependant on the irradiation fluence

High efficiency dye-sensitized solar cell based on a novel gel polymer electrolyte containing RbI and tetrahexylammonium iodide (Hex4NI) salts and multi-layered photoelectrodes of TiO2 nanoparticles

High efficiency dye sensitized solar cells (DSSCs) have been achieved using a novel polymer gel electrolyte containing RbI and tetrahexylammonium iodide (Hex4NI) binary salts in combination with multi-layered TiO2 photoelectrodes. Performance enhancers were incorporated to the electrolyte to improve the efficiency in the DSSCs. Varying the salt mass fraction, showed that the conductivity in the electrolyte increases with increasing amount of RbI. The highest ionic conductivity of 4.19 mS cm−1 is exhibited by the electrolyte sample with RbI:Hex4NI weight ratio of 3:1 at 25 \ub0C. The temperature dependence of the electrolytes shows Arrhenius behavior. It is found that the electrolyte with RbI:Hex4NI weight ratio of 1.06:1 is more suitable for DSSC\u27s applications and it has a conductivity of 3.77 mS cm−1. A colloidal suspension of P25 TiO2 nanoparticles was used to make the spin coated photo-anodes in the form of stacks of 1–6 layers. The formation of a highly uniform and porous structure is observed with increasing number of layers from scanning electron microscopy and X-ray diffraction studies revealed that the layers are predominantly anatase phase with crystallite size of 19–22 nm. The band gap was estimated to be around 3.22 eV based on UV–Visible spectroscopy and found to be decreasing slightly with increasing layer thickness. The maximum efficiency of 7.5% and an impressively high current density of 20 mA cm−2 were observed for the 4-layer device with the new gel electrolyte based on RbI and Hex4NI. This study not only brings reliability and consistency to the ways of preparing well-ordered TiO2 photo-anodes but also offers the possibility of low-cost practical and highly efficient quasi-solid state DSSCs