A baseline process has been established for CuInS2 solar cells. Stable efficiencies in the range of 10-11% on small area single solar cells are achieved with this technology, the best cell so far has reached 11.4% (total area). This baseline technology serves as base for further improvements at various steps of the whole process. Additionally integrated series connected mini-modules on 5 X 5 cm(2) substrates have been prepared with the same technology. The majority of these mini-modules are in the range of 8-9% efficiency with 9.7% for the best one. These modules show open circuit voltages per cell that are identical to those achieved with good single cell devices, whereas fill factor and short circuit current density are still somewhat lower. The gap between single solar cells and mini-modules, however, is less than 2% absolute in efficiency, a rather small difference. Analysis of modules with 8-9% efficiency using an infrared camera system reveals hot spots that are due to small shunts. These small shunts are a major reason for non-optimum efficiency. Modules and cells show stable performance throughout 2000 h exposed to dry heat (85degreesC). (C) 2003 Elsevier Science B.V. All rights reserved.