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

Abstract Typical fabrication methods for laboratory‐scale (<1 cm 2 ) 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, CsPbBr 3 and KPb 2 Br 5 , to the perovskite precursor ink for enabling homogeneous and highly crystalline large‐area Cs 0.15 FA 0.85 Pb(I 0.83 Br 0.17 ) 3 (CsFA) perovskite films via scalable slot‐die coating technique. X‐ray photoelectron spectroscopy analysis reveals the segregation of potassium ions at SnO 2 /perovskite interface which serve as nucleation sites for the crystallization of perovskite layer. The uniformly slot‐die coated CsFA films (100 cm 2 ) 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 cm 2 shows an efficiency of 16.22% and retains 82% of its initial efficiency after 4800 h under 30% relative humidity without encapsulation.