CuInS2 thin film formation on a Cu tape substrate for photovoltaic applications

A new technique, "CISCuT'', for the preparation of polycrystalline single-phase CuInS2 thin films for solar applications has been developed. In a continuous roll-to-roll process a copper tape is at first electrochemically plated with an In layer. This tape undergoes in a second step at about 600 degrees C a rapid sulfurization process at atmospheric pressure. Structural and electrical characterization (XRD, SEM, TEM, EDXS, I/V-characteristics) reveals that in this high-speed, highly productive process photoactive CuInS2 is formed. Single-phase CIS films of about 1.5 mu m thickness, consisting of grains with 1-2 mu m lateral dimensions are grown. The present state of understanding of the CuInS2 formation is discussed in some detail. First solar cells prepared from this material show efficiencies around 6%. The new experimental approach described here is promising to become an effective low-cost method for the production of thin-film CIS absorber layers without any vacuum step. The continuous growth process from roll to roll is possibly a way to make solar cell and modul production competetive with conventional energy generation. (C) 1998 Elsevier Science B.V. All rights reserved.