Peeling-Off Process for the Fabrication of Flexible, Lightweight Bifacial Perovskite/Cu(In,Ga)Se2 Tandem Solar Cells

In this study, a peeling-off technique is developed for fabricating flexible, lightweight, and bifacial perovskite/Cu(In,Ga)Se₂ (CIGSe) tandem solar cells (TSCs). The process involves forming a perovskite/CIGSe TSC on a glass substrate and then peeling it off. The effectiveness of the proposed process is investigated using a CIGSe single-junction solar cell. A MoSe₂ atomic layer with a c-axis orientation is observed at the Mo/CIGSe interface, which promotes the peeling-off process. A flexible, lightweight CIGSe solar cell with a power conversion efficiency (PCE) of 12.3% is fabricated using the peeling-off technique. The open-circuit voltage of the flexible solar cell is similar to that of the rigid CIGSe solar cell. Furthermore, a perovskite/CIGSe TSC is fabricated with a PCE of 21.4% on a glass substrate. The TSC exhibited excellent current matching owing to the good match between the energy bandgaps of the perovskite and CIGSe. The proposed technique is used to detach the TSC from the substrate, and NiO and In₂O₃ transparent back layers are deposited on the peeled CIGSe rear surface. The device exhibits rectification and a PCE of 2.9%. Scanning electron microscopy reveals that the SnO₂/C60 and/or C60/perovskite interfaces are peeled off. These results demonstrate that high-efficiency, flexible, lightweight, and bifacial perovskite/CIGSe TSCs can be fabricated using the proposed technique by controlling adhesion at the device interfaces.