Synthesis characterization and electrochemical performance of chromium doped tin oxide

Chromium doped Tin oxide nanoparticles with chromium concentrations ranging from 1 to 5 wt% were synthesized by microwave irradiation technique. Standard characterization techniques were used to understand the characteristics of the nanoparticles obtained. X-Ray Diffraction (XRD) pattern depicted the tetragonal crystal structure for Cr doped SnO2 nanoparticles. From the results of crystallite sizes for various doping concentrations, it was observed that doping inhibits the growth of crystalline grains of SnO2. Scanning Electron Microscope (SEM) images confirmed the surface morphology modifications due to varying doping concentration of Cr, nanocrystallite showed extra agglomerated status with mesoporous structures. Energy dispersive spectrometer (EDAX) observations confirmed the doping of chromium ions in SnO2 lattice. Other standard characterization techniques such as FESEM, TEM, HRTEM, FTIR, UV-Vis spectroscopic analysis were also carried out for the samples prepared. The electrochemical behavior of the sample was determined using Cyclic Voltammetry (CV) by scanning the potential at a rate of 50 mV s‾¹ and for a maximum current of 600 mA carried out on undoped SnO2 and Cr doped SnO2. It was observed that as the wt% of Cr in Cr doped SnO2 increases, the electrochemical performance increases as compared to undoped SnO2. A fairly larger peak current of 15 μA and a larger oxidation peak potential of 0.76 V were observed for 5 wt% Cr doped SnO2.

Synthesis and Characterization of Ni2+-doped SnO2 Powders

The SnO2:Ni2+ powders with dopant contents ranging from 0.0 to 12 mol% have been synthesized by sol-gel method. The samples were characterized by X-ray diffraction (XRD) Raman spectroscopy, energy-dispersive X-ray spectrometer (EDS) and photoluminescense (PL) spectra. XRD analysis showed that samples doped with low Ni- concentrations exhibited single SnO2 crystalline phase, whereas the samples with high Ni- concentrations exhibited a mixture of SnO2 and NiO phases. The lattice parameters of the SnO2 host were independent on Ni2+ dopant content, while Raman mode positions were dependenton Ni2+ dopant content. The PL spectrum of the undoped SnO2 was characterized by the emission peaks due to near band edge (NBE) emission and the violet emission peaks associated with surface dangling bonds or oxygen vacancies and Sn interstitials.

CdS/CdTe Heterostructures for Applications in Ultra-Thin Solar Cells

The preparation of ultra-thin semi-transparent solar cells with potential applications in windows or transparent roofs entails several challenges due to the very small thickness of the layers involved. In particular, problems related to undesired inter-diffusion or inhomogeneities originated by incomplete coverage of the growing surfaces must be prevented. In this paper, undoped SnO2, CdS, and CdTe thin films with thickness suitable for use in ultra-thin solar cells were deposited with a radiofrequency (RF) magnetron sputtering technique onto conductive glass. Preparation conditions were found for depositing the individual layers with good surface coverage, absence of pin holes and with a relatively small growth rate adapted for the control of very small thickness. After a careful growth calibration procedure, heterostructured solar cells devices were fabricated. The influence of an additional undoped SnO2 buffer layer deposited between the conductive glass and the CdS window was studied. The incorporation of this layer led to an enhancement of both short circuit current and open circuit voltage (by 19 and 32%, respectively) without appreciable changes of other parameters. After the analysis of the cell parameters extracted from the current-voltage (I-V) curves, possible origins of these effects were found to be: Passivation effects of the SnO2/CdS interface, blocking of impurities diffusion or improvement of the band alignment.