The influence of H2Se annealing procedure on the material quality of CuInSe2 films

The importance of photovoltaics (PV) as an energy source of great potential in the 21st century is well known. Among the many candidates for PV, polyc rystalline CuInSe2 (CIS) thin-film solar cells seem to be among the most fa vourable due to their high conversion efficiencies, durability and low prod uction costs. The reaction of metallic alloys to H2Se/Ar is a promising tec hnique to produce device-quality CIS material. Hitherto, the reproducibilit y of this growth technique has been questioned because of loss of material during selenization. Attempts to solve this problem by optimization of the metallic alloys, before selenization, were unsuccessful. In this contributi on, the material properties of the final films were evaluated as a function of various selenization conditions. From this fundamental study, we demons trated that improved reproducibility can be obtained by the rapid heating o f metallic precursors in H2Se. Transmission electron microscopy revealed la rge, faceted grains with low defect densities. Photoluminescence studies co nfirmed the superior properties of these films. Variations in the intensity and energy of the observed transitions at different selenization temperatu res has been attributed to variation in the intrinsic defect density of sel enium vacancies.