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

Abstract 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 Cs0.15FA0.85Pb(I0.83Br0.17)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.