Midsummer has an extensive R&D operation. We have developed our own, all sputtering process that is supplied with the tool. As a customer you test, verify performance and accept the equipment at our factory prior to delivery. This is unique to Midsummer and ensures the quality of equipment and process as well as a short start up time. Unlike Roll-to-Roll solutions, the Midsummer tool produces individual cells on punched stainless steel substrates. This allows for making flexible modules while keeping cell uniformity and performance at an optimum to reduce manufacturing costs and give a high yield.
CIGS stands for Copper-Indium-Gallium-Selenium, a tetrahedrally bonded semiconductor, with chalcopyrite crystal structure that converts the energy of light directly into electricity by the photovoltaic effect (PV). The CIGS absorber and all other materials that form the finished solar cell are deposited on a stainless steel substrate. The cells are then connected in series via bus bars screen printed on top of the cell outside of the DUO.
CIGS solar cells are manufactured by sputtering the material onto 156x156 mm stainless steel substrates. The solar cells from Midsummer are free of cadmium, a toxic material usually used in CIGS and other thin film solar cells. Flexible CIGS solar modules are gaining market share thanks to its high efficiency, low weight, flexibility and durability.
Since a stainless steel substrate is used, the solar panels can be made with a plastic front sheet instead of the glass that is required for silicon cells to avoid cracks. The CIGS solar modules are therefore much lighter, flexible and can be made frameless to suit applications where traditional silicon solar panels cannot be used, e.g. on structures that are uneven, moving or weak. Furthermore, the CIGS technology works better in low lights and at higher temperatures meaning you get more kWh per installed kW.
Midsummer do not scribe the solar cells. The voltage increase is achieved by stringing the cells together in the solar panel, just like in conventional silicon panels. This leads to a higher yield and fewer rejects compared with other thin film technologies. Midsummer’s proven technology conforms to the IEC 61646 and IEC 61730 criteria
Midsummer’s R&D is carried out on the same equipment and with the same substrate size that is being used for mass production. This ensures proven production solutions and smooth transfer of new processes and technologies. Unlike producers of large turnkey lines, Midsummer has an identical production line running in its R&D and production facility in Sweden. Recently there has been a significant improvement in the cell performance with the aperture area efficiency reaching above 17.04% over the whole 6” cell, corresponding to 14.87% in total area efficiency. The results have been reached with non-cadmium, all-vacuum process and with a CIGS layer of less than 1 micron in thickness.