J.K.D.S. Jayanetti

Electrodeposition and characterisation of CuInSe2 for applications in thin film solar cells

Copper indium diselenide (CuInSe2) layers have been grown at room temperature by electrochemical deposition technique in an aqueous medium. Resulting thin films have been characterised using XRD, XRF, XPS, GDOES and SEM for structural, stoichiometric and morphological properties. A considerable influence of the deposition potential on the atomic composition of In and Se present in the film was observed. Cu composition remains the same within the deposition potentials used in this investigation. The deposited layers are polycrystalline and annealing at 350 degreesC for 30 min improves the crystallinity. The film quality deteriorates due to dissociation when annealed at temperatures above 350 degreesC. Excessive annealing results in a surface which is depleted in Cu and rich in In and Se

Sulfidation of electrodeposited microcrystalline/nanocrystalline cuprous oxide thin films for solar energy applications

Grain size of polycrystalline semiconductor thin films in solar cells is optimized to enhance the efficiency of solar cells. This paper reports results on an investigation carried out on electrodeposited n-type cuprous oxide (Cu2O) thin films on Ti substrates with small crystallites and sulfidation of them to produce a thin-film solar cell. During electrodeposition of Cu2O films, pH of an aqueous acetate bath was optimized to obtain films of grain size of about 100 nm, that were then used as templates to grow thicker n-type nanocrystalline Cu2O films. XRD and SEM analysis revealed that the films were of single phase and the substrates were well covered by the films. A junction of Cu2O/CuxS was formed by partially sulfiding the Cu2O films using an aqueous sodium sulfide solution. It was observed that the photovoltaic properties of nano Cu2O/CuxS heterojunction structures are better than micro Cu2O/CuxS heterojunction solar cells. Resulting Ti/nano Cu2O/CuxS/Au solar cell structure produced an energy conversion efficiency of 0.54%, V-oc = 610 mV and J(sc) = 3.4 mA cm(-2), under AM 1.5 illumination. This is a significant improvement compared to the use of microcrystalline thin film Cu2O in the solar cell structure where the efficiency of the cell was limited to 0.11%. This improvement is attributed mainly to the increased film surface area associated with nanocrystalline Cu2O films.

The magnetic properties of Sm‐Ti‐Fe and Nd‐Ti‐Fe hard and soft sputtered phases

A series of Sm‐Ti‐Fe and Nd‐Ti‐Fe film samples have been synthesized by rf diode sputtering for Fe‐rich compositions. Samples have been directly crystallized onto heated substrates as well as first deposited amorphous and then subsequently crystallized. In the film plane magnetic fields have been applied during the deposition and during the crystallization to induce in‐the‐film‐plane anisotropies into the films. A phase that contained only Sm, Ti, and Fe has been synthesized in film form that exhibited an in‐plane intrinsic coercive force, iHc, of 31 kOe at room temperature and 58 kOe at 5 K. Tetragonal lattice parameters with a=8.391 A and c=12.297 A have been assigned to the high iHc phase by a fitting to 12 diffraction lines. The Nd‐Ti‐Fe and the Sm‐Ti‐Fe systems also exhibited a soft magnetic phase of the ThMn12‐type at a nominal composition of Nd(TiFe11).

Ammonium sulfide surface treatment of electrodeposited p-type cuprous oxide thin films

The effects of ammonium sulfide surface treatment on electrodeposited p-type polycrystalline cuprous oxide (Cu2O) thin films deposited on Ti substrates were studied. The structural and morphological properties of the films were investigated using scanning electron microscopy, x-ray diffraction, and energy-dispersive x-ray spectroscopy. The changes in the conductivities and photocurrents of the films after the ammonium sulfide treatment were determined. Films that had undergone the ammonium sulfide treatment showed reduced resistivities, enhanced spectral photoresponses, and enhanced current-voltage characteristics. The results showed that ammonium sulfide treatment improved the peak output current of the p-type Cu2O films by about 400% compared with those of bare Cu2O films. This improvement is attributed to the passivation of defects in the films by sulfur, showing that sulfur passivation provides a good method for improving of Cu2O-based devices.

X-ray study of interfacial interactions in highly milled Sn-Ge powders

We have studied possible structural changes occurring at the Sn/Ge interface of highly milled Sn/Ge composites. EXAFS and X-ray Diffraction measurements were made on mechanically milled powders having compositions ranging from 20 to 50 vol.% Sn. X-ray diffraction measurements indicate the increasing amorphization of Sn as the Sn content is decreased. EXAFS results indicate that this amorphous phase is due to the formation of an {alpha}-Sn/Ge alloy. The EXAFS from this alloy did not change significantly at the Sn melting point. X-ray diffraction measurements made at room temperature show a systematic decrease in the intensity of Sn peaks and broadening of Ge peaks with the decreasing Sn content.