Roll-to-roll laboratory system for deposition of CIGS solar cells on films
Solar energy is not only free but – with some time restrictions – it is also available everywhere. Solar cells are lighter and less expensive than carrying energy in the form of batteries or fuel to areas where being separated from the grid is unavoidable, such as in stationary systems in remote locations, in mobile outdoor applications or in satellites. Solar cells also need to be very light for installation on roofs that are not structurally engineered for heavy panels, or even for canvas.
Requirements for the systems
The two pilot systems are designed to coat film with solar cells in a roll-to-roll process. The one system sputters the transparent and the metallic electrodes, the other one applies the CIGS absorber layers by means of thermal evaporation. The systems are used for process development and production of samples but they are not ready for mass production yet. For that reason, the systems need to be large enough to meet realistic process conditions in production, but they should not be larger than that because of the cost of the system, the substrate and the coating materials. As pilot plants, they also need to be extremely flexible, since the process details and perhaps even the layer structure may still change.
Solutions to requirements
The two roll-to-roll systems have already been built similarly for a number of other R & D projects and can coat films with widths of 300 mm and lengths up to 500 m – typical values for a pilot system. Both systems are constructed almost identically from the winding system on: The film is wound, unwound and spread in the upper part of the systems, while the processing units – rotary cathodes with their rotary targets or evaporators, respectively – are arranged around the process drum in the lower part of the system. The temperature of the process drum can be controlled because the substrate temperature is crucial for the proper formation of the layers. The full-face front door and the two large side doors provide convenient access to all parts of the system. Additional flanges allow components to be retrofitted.
The special features of this system are:
- Flexible system design for R&D in roll-to-roll processes
- Available in both sputtering and evaporation configurations
- Integration of in-situ measurement technology, such as XRD
- Process drum is water cooled or can be heated to well over 200 °C
- Automated coating with full control over all winding and process parameters