3 research outputs found
Chemical incorporation of copper into indium selenide thin-films for processing of CuInSe2 solar cells
A chemical method of incorporating copper into indium selenide thin-films has been
investigated, with the goal of creating a precursor structure for conversion into
CuInSe2 layers suitable for solar cell processing. The precursor and converted layers
have been investigated with scanning electron microscopy, x-ray diffraction, Raman
spectroscopy and x-ray photoelectron spectroscopy. From these measurements, the
incorporation of copper into the indium selenide layers is concluded to proceed by an
ion-exchange reaction. This reaction results in the formation of a precursor layer with
a graded compositional depth-profile containing the crystalline phases In2Se3 and
Cu2-xSe. Selenization of the precursor layer homogenises the composition and forms
chalcopyrite CuInSe2. These CuInSe2 layers exhibit a dense microstructure with
rough surface morphology, which is ascribed to a non-optimal selenization process.
Solar cells with the structure ZnO:Al/i-ZnO/CdS/CuInSe2/Mo/Glass have been
processed from the selenized layers and have exhibited efficiencies of up to 4% under
simulated AM1.5 illumination
Incorporation of copper into indium gallium selenide layers from solution
A chemical method for the incorporation of copper into indium gallium selenide (IGS) layers has been developed. The resulting copper-containing precursor layers have been annealed in the presence of selenium vapour with the goal of forming Cu(In, Ga)Se2 (CIGS) layers. It is found that copper ions in solution are incorporated into IGS layers during immersion, resulting in the formation of a precursor layer containing both copper selenides and IGS. When aqueous solutions are used for this process, corrosion of the molybdenum back contact occurs by reduction of copper ions in the solution. Use of an ethylene glycol solution prevents corrosion of the Mo and allows higher process temperatures, corresponding to higher reaction rates. During annealing, the precursor layers are converted into CIGS and the morphology of these layers is strongly affected by the availability of selenium whilst the substrate temperature is ramped up
Structural properties of Cu(In,Ga)Se2 thin films prepared from chemically processed precursor layers
We have developed a chemical process for incorporating copper into indium gallium selenide layers with the goal of creating a precursor structure for the formation of copper indium gallium diselenide (CIGS) photovoltaic absorbers. Stylus profilometry, EDX, Raman spectroscopy, XRD and SIMS measurements show that when indium gallium selenide layers are immersed in a hot copper chloride solution, copper is incorporated as copper selenide with no increase in the thickness of the layers. Further measurements show that annealing this precursor structure in the presence of selenium results in the formation of CIGS and that the supply of selenium during the annealing process has a strong effect on the morphology and preferred orientation of these layers. When the supply of Se during annealing begins only once the substrate temperature reaches ≈ 400 °C, the resulting CIGS layers are smoother and have more pronounced preferred orientation than when Se is supplied throughout the entire annealing process