Laminated Two-Terminal All-Perovskite Tandem Solar Cells with Transparent Conductive Adhesives

Established sequential deposition of multilayer two-terminal (2T) all-perovskite tandem solar cells possesses challenges for fabrication and limits the choice of materials and device architecture. In response, this work represents a lamination process based on a transparent and conductive adhesive that interconnects the wide-bandgap (WBG) perovskite top solar cell and the narrow-bandgap (NBG) perovskite bottom solar cell in a monolithic 2T all-perovskite tandem solar cell. The transparent conductive adhesive (TCA) layer combines Ag-coated poly(methyl methacrylate) microspheres with an optical adhesive. The TCA is employed as a recombination junction, achieving self-encapsulation with high transparency and good conductivity. A high vertical electrical conductivity is realized by optimizing the distribution of microspheres using a novel solidification strategy that employs UV curing and drying at 85 °C at low pressure. In addition, uniform and dense bilayer hole transport layers are realized by vapor-phase evaporation, which facilitates the application of the TCA and achieves pinhole-free buried interfaces in both the WBG perovskite top solar cell and the NBG perovskite bottom solar cell. Using these two strategies, losses in fill factor (FF) and open-circuit voltage (V_OC) of the 2T all-perovskite tandem solar cell are reduced, achieving a respectable power conversion efficiency up to 18.2% for the lamination of the all-perovskite tandem solar cell. The laminated tandem solar cell retains ∼93% of initial efficiency after exposure in ambient air (30-70 RH% and 20-35 °C) for ∼30 days.