Abstract
Perovskite-CIGS thin-film tandem solar cells could potentially share vacuum-based production equipment between sub-cells, reducing CapEx and supply chain dependence while enabling flexible, lightweight designs for versatile photovoltaic applications. However, scalable vacuum-based fabrication techniques for perovskite-CIGS tandems remain limited and challenging. Here, a highly efficient and stable bilayer methylammonium lead iodide perovskite fabricated using a scalable co-evaporation technique is presented. In this bilayer structure, an additional thin layer with an enhanced PbI₂ evaporation rate is deposited atop a thick stoichiometric perovskite film. This approach reduces film roughness and improves the contact potential difference at the perovskite interface. For the first time, this interface engineering strategy enhances absorber film stability, enabling the deposition of a SnO(x) buffer layer via atomic layer deposition without damaging the perovskite layer. The bilayer film is used to fabricate single-junction solar cells, achieving a maximum power conversion efficiency of 23.1%, with over 93% of its efficiency retained after 500 h of continuous maximum power point tracking. Ultimately, its compatibility for tandem applications is demonstrated, leading to the fabrication of fully laminated perovskite-CIGS tandem solar cells with an efficiency of 26.1%, surpassing the current record for monolithic perovskite-CIGS tandems at the same 1 cm(2) active area. The sub-cells are integrated via POE lamination, a widely adopted industrial process, ensuring compatibility with large-scale manufacturing.