Unveiling the Role of Cl Incorporation Enables Scalable MA‐Free Triple‐Halide Wide‐Bandgap Perovskites for Slot‐Die‐Coated Photovoltaic Modules

Photostable and efficient 1.8 eV wide‐bandgap (WBG) perovskites are needed for all‐perovskite tandem photovoltaic (PV) applications, but the high bromine (Br) content can cause halide segregation. To achieve the same bandgap with a lower Br content, MAPbCl 3 can be added to form triple‐halide perovskites. However, most triple‐halide WBG perovskites are still fabricated by antisolvent spin coating with perovskite inks that cannot be transferred to scalable deposition methods. Furthermore, the role of the Cl additives on the bandgap and the photostability remains elusive. Here, Cl‐additives, such as ACl, PbCl 2 , and APbCl 3 (where A denotes MA, FA, Cs, Rb), are systematically investigated to form 1.8 eV triple‐halide perovskites with 30 mol% Br by N 2 ‐assisted blade coating. It is found that PbCl 2 and APbCl 3 can increase the bandgap by several tens of meV, while ACl can only increase the bandgap by few meV. CsPbCl 3 emerges as a promising alternative to MAPbCl 3 , enabling 17.2% efficient MA‐free 1.8 eV triple‐halide perovskite solar cells (0.062 cm 2 ) with enhanced phase‐ and photostability. Its scalability is demonstrated by slot‐die coating a ≈10% efficient WBG perovskite solar module with an aperture area of 52.8 cm 2 .