Alkali Additives Enable Efficient Large Area (>55 cm²) Slot-Die Coated Perovskite Solar Modules

Typical fabrication methods for laboratory-scale (<1 cm²) perovskite solar cells (PSCs) are undeniably not scalable and the control of crystallization of large-area perovskite layer for commercial sized modules is also particularly challenging. Here, a seed-assisted crystallization approach is demonstrated through addition of alkali salts, CsPbBr₃ and KPb₂Br₅, to the perovskite precursor ink for enabling homogeneous and highly crystalline large-area Cs_0.15FA_0.85Pb(I_0.83Br_0.17)₃ (CsFA) perovskite films via scalable slot-die coating technique. X-ray photoelectron spectroscopy analysis reveals the segregation of potassium ions at SnO₂/perovskite interface which serve as nucleation sites for the crystallization of perovskite layer. The uniformly slot-die coated CsFA films (100 cm²) from the additives containing precursor inks possess larger grains with enhanced optoelectronic properties and the corresponding devices display higher reproducibility and consistency. A champion device efficiency of 18.94% under 1 sun illumination for slot-die coated PSCs in n-type/intrinsic/p-type structure is demonstrated with improved stability with 82% of its initial efficiency tested at 65 °C for 1150 h. The slot-die coated methylammonium-free perovskite module with an active area of 57.5 cm² shows an efficiency of 16.22% and retains 82% of its initial efficiency after 4800 h under 30% relative humidity without encapsulation.