Upscaling of Perovskite-Silicon Tandem Solar Cells

We are working on upscaling of perovskite-silicon tandem solar cells from small lab size areas of several square millimeters to full commercial wafer size. This requires the use of processing techniques that can replace the usual spin coating process employed for small lab size areas. As alternatives for large-area depositions spray coating, inkjet printing and slot-die coating are investigated. For highest specific energy yield under field conditions perovskitesilicon tandem solar cells should be textured on the front side. To ensure conformal coating of the random pyramid textured silicon bottom cell we follow a hybrid process route. In a first step, the inorganic components are thermally evaporated to form a scaffold allowing conformal coating of pyramids of arbitrary size and shape. In a second step, the conversion into perovskite is accomplished by infiltration of the scaffold with organic salt solutions. A thermal anneal completes the conversion into a polycrystalline perovskite layer. In addition to upscaling of the cell area we work on replacing the evaporated silver contact grid by screen printed ultralow temperature silver paste. First results on planar perovskite-silicon tandem solar cells, still fabricated with spin coating processing but with screen-printed front contacts, resulted in a certified stabilized conversion efficiency of 22.5% on 104 cm2 total cell area.