It is known that tungsten oxide may be reacted with selenium sources to form WSe2 but literature reports include processing steps that involve high temperatures, reducing atmospheres, and/or oxidative pre-treatments of tungsten oxide. In this work, we report a non-vacuum process for the fabrication of compositionally high quality WSe2 thin films via the selenization of tungsten oxide under milder conditions. Tungsten source materials were various hydrated WO3 and WO2.9 compounds that were prepared using chemical solution techniques. Resulting films were selenized using a two-stage heating profile (250 °C for 15 minutes and 550 °C for 30 minutes) under a static argon atmosphere. Effects of the starting tungsten oxide phase on WSe2 formation after single and double selenization cycles were investigated using Raman spectroscopy and X-ray diffraction (XRD). After two selenization cycles, hydrated WO3 was converted to (002)-oriented WSe2 that exhibits well-resolved peaks for E12g and A1g phonon modes. Only a single selenization cycle was required to convert amorphous WO2.9 to WSe2. All selenizations in this work were achieved in non-reducing atmospheres and at lower temperatures and shorter times than any non-laser-assisted processes reported for WO3-to-WSe2 conversions.

A cadmium chloride activation treatment is essential for the production of high efficiency cadmium telluride (CdTe) solar cells. However, the effects of the treatment on the distributions of chlorine and sulphur within the device are not fully understood. Here, the detailed locations of chlorine and sulphur in a treated CdTe cell are determined in three dimensions by high resolution dynamic SIMS measurements. Chlorine is found to be present in grain boundaries, grain interiors, extended defects within the grain interiors, at the front interface, and in the cadmium sulphide layer. In each of these regions, the chlorine is likely to have significant effects on local electronic properties of the material, and hence overall device performance. Sulphur is found to have a U-shaped diffusion profile within CdTe grains, indicating a mixed grain boundary and lattice diffusion regime.

We present the defect analysis by photoluminescence (PL) spectroscopy of CdSexTe1-x thin films, grown with varying Se content by a co-sputtered deposition method. We observe a peak at 1.203 eV in the CdSexTe1-x film for x = 0.21, which shifts towards higher energies with increase in laser power. This peak was assigned to a donor-to-acceptor (DAP) transition, with a measured j-shift of ∼4.7 meV/decade. Temperature dependent PL intensity measurements confirm that the observed DAP peak involves a shallow defect state of binding energy ∼34.7 meV. In contrast, a free-to-bound (FB) peak at 1.294 eV involving a shallow defect of binding energy ∼18.3 meV was observed in the CdSexTe1-x film for x = 0.14. Additionally, we observe band edge emission at 1.452 eV and 1.448 eV in CdSexTe1-x films for x = 0.14 and x = 0.21 respectively. Our analysis shows that the Se concentration not only changes the band gap energy of the resulting CdSexTe1-x alloy thin film, but also modifies the nature of the dominant observed defect emission.

The chemical bath deposition of wide bandgap n-type SnS2 films and role of sulphur precursor in suppression of p-type SnS phase is described. The as-deposited films are highly polycrystalline in hexagonal crystal structure. Inclusion of oxygen in the film phase is shown by the x-ray photoelectron spectroscopy (XPS) and Raman scattering methods which suggests the CBD films are better described as tin disulfide-oxide (SnS2-xOx) x=0.1. A possible mechanism of film formation is presented. Optical analysis showed energy bandgap 2.76 eV for SnS2-xOx film which decreases to 2.62 eV with the inclusion of the secondary SnS phases.

The deposition of uniform, reproducible and compact Sb2S3 thin films were obtained by chemical bath deposition using tartaric acid as a complexing agent. It was found that the thickness of the films increases with the pH of the solution, reaching values of 130 and 170 nm for pH values of 9.5 and 10, respectively. XRD, as well as Raman analysis, showed amorphous Sb2S3 films formed directly from the chemical bath, which crystallized into stibnite after a thermal treatment in N2 with crystallite sizes between 31 and 39 nm. On the other hand, the optical band gap of the Sb2S3 films decreased with an increase in pH, with values of 1.82-2.03 eV for the crystalline ones. An n-type photo-conductivity of 10-6 Ω-1 cm-1 was obtained for the heated films. The evaluation of these films for solar cell applications using CdS as the window layer gave a Voc of 656 mV and a Jsc of 2.66 mA/cm2 under AM1.5G radiation.

We report first principles spin-polarized density functional theory calculations to study the electronic structure of pure and Magnesium doped (replacing Al) CuAlO2 and AgAlO2 transparent conducting oxides in the hexagonal 2H structural phase. Hole effective masses are obtained from the band structure. Additionally, the complex dielectric function is obtained. A discussion of the effects of Mg-doping on the optical properties and its effectiveness in reducing hole effective masses and increasing conductivity is also presented.

Alloys of the CuAlS2 – CuFeS2 system were prepared by thermobaric treatment at high pressure of 5.5 GPa and temperatures ranging from 573 to 1573 K and phase formation in the system was investigated using X-ray powder diffraction, optical microscopy and scanning electron microscopy equipped with energy dispersive spectroscopy. The unit-cell parameters (the lattice constants and the unit-cell volume) were computed as a function of the composition. Absence of complete solubility in the (CuAlS2)1-x-(CuFeS2)x system was established. Formation of solid solutions with the tetragonal structure of chalcopyrite was detected for compositions with the molar part of CuFeS2 x not exceeding 0.10.