なかのにっき

CuInSe2 films of various stoichiometries have been prepared by the two-stage process. In this method, Cu-In layers were first evaporated onto Mo-coated glass substrates in the form of stacks, and then they were selenized in a H2Se atmosphere at 400 °C to form the compound. CdZnS/CuInSe2 heterojunction solar cells were fabricated on these films and conversion efficiencies close to 7% were obtained.

Abstract CuInSe2 films have been prepared using the selenization technique. Preparation of the precursor as well as selenization were carried out by the vacuum evaporation technique. The sequence of copper and Indium layer deposition during precursor preparation affects the morphological and structural properties of precursor which directly have effects on the properties of selenized CIS films. A thin layer of amorphous selenium at the substrate/film interface has been used to improve the adherence of the film. The effect of the Se under-layer has been studied on the layers of copper, indium, CuIn precursors and CIS films, using structural, morphological and optical properties. The surface morphology of a single layer of copper and indium, with and without the Selenium under-layer, are quite different and drastically affect the properties of the precursor and selenized films. The Se under-layer does not take part in the chemical reaction of CIS formation during the selenization process. The modified CIS films are uniform, single phase, polycrystalline, chalcopyrite with (1 1 2) preferred orientation showing an energy band gap of 0.99 eV and an absorption coefficient of ~10^5 cm-1, and have good adherence to the substrate for the scotch tape test.

CuInS2 films were synthesized by sulphurization of In/Cu stacked elemental layers (SEL) deposited onto glass and Mo-coated glass substrates by graphite box annealing at temperatures of 620-880 K. The films thus synthesized were characterized by measuring electrical, optical, microstructural and photoluminescence properties. The microstructure and hence the physical properties of the films depended critically on the amount of sulphur incorporation. Nature of charge carriers depended on both Cu/In and S/(Cu+In) ratio and the carrier concentration varied between 10^14 and 10^18 cm^-3. Grain boundary scattering effects were critically studied by measuring the electrical conductivity and Hall mobility simultaneously on the same sample. The shape of the grains depended critically on the sulphur content. The PL spectra were dominated by the excitonic peak ~788 nm followed by another peak at ~892 nm which may be ascribed to the DA transition.