Ostwald Ripening–Mediated Grain Coalescence for High‐Quality Blade‐Coated Tin–Lead Perovskites and Tandem Solar Cells

Abstract All‐perovskite tandem solar cells (TSCs) hold great promise for surpassing the Shockley–Queisser limit of single‐junction solar cells. However, scaling up TSCs remains challenging because of the lower efficiency of blade‐coated mixed tin–lead (Sn‐Pb) perovskites compared to their spin‐coated counterparts. Unlike antisolvent‐induced high‐quality crystallization, blade‐coated Sn‐Pb perovskite films often exhibit pinholes, uneven textures, and disordered grains due to the limited extraction capability of the air knife during deposition. In this study, malonamidine hydrochloride is introduced as an Ostwald ripening mediator to promote grain coalescence, enabling the formation of smooth and compact films. Benefiting from improved crystallographic orientation and reduced internal stress, the resulting single‐junction Sn‐Pb perovskite solar cells exhibited a high efficiency of 21.06%. Furthermore, 4‐terminal and 2‐terminal blade‐coated all‐perovskite TSCs exhibited impressive efficiencies of 28.45% and 27.25%, respectively. This study not only provides insights into nucleation and crystallization during the blade‐coating process for Sn–Pb perovskites but also offers an effective strategy for fabricating high‐quality Sn‐Pb perovskite films, paving the way for scalable, high‐performance TSCs.