Inorganic wide-bandgap perovskite subcells with dipole bridge for all-perovskite tandems

Operating stability has become a priority issue for all-perovskite tandem solar cells. Inorganic CsPbI_3−xBr_x perovskites, which have good photostability against halide segregation, are promising alternatives for all-perovskite tandem solar cells. However, the interface between organic transport layers and inorganic perovskite suffers from a large energetic mismatch and inhibits charge extraction compared with hybrid analogues, resulting in low open-circuit voltages and fill factors. Here we show that inserting at this interface a passivating dipole layer having high molecular polarity—a molecule that interacts strongly with both inorganic perovskite and C₆₀—reduces the energetic mismatch and accelerates the charge extraction. This strategy resulted in a power conversion efficiency (PCE) of 18.5% in wide-bandgap (WBG) devices. We report all-perovskite tandems using an inorganic WBG subcell, achieving a PCE of 25.6% (steady state 25.2%). Encapsulated tandems retain 96% of their initial performance after 1,000 h of simulated 1-sun operation at the maximum power point.