Controlling Film Formation in Inkjet‐printed MAPbBr ₃ Through Graphene Incorporation for Enhanced Photodetection

ABSTRACT The exceptional optoelectronic properties and solution processability of metal halide perovskites make them promising candidates for realizing high‐performance devices via additive manufacturing techniques like printing. The composition of inks used therein plays a vital role in thin film formation, critically influencing optical conversion and electrical transport in devices. However, understanding and controlling film formation in printed perovskite layers remains largely elusive. Presented herein are investigations on the influence of adding graphene flakes into precursor inks of methylammonium lead bromide (MAPbBr ₃ ) for enhancing printed photodetector performance. Direct visualization of the film formation process suggests that the graphene flakes induce a delay in nucleation and modulate crystallization kinetics, promoting a transition from isolated island growth to extended dendritic structures. While optical properties remained unaffected, longer carrier lifetimes, homogeneity in composition, and lowering of work functions were observed in films containing graphene, leading to superior device performance. With single‐pass printing, photodetectors with responsivities up to 3.54 A·W ⁻¹ , detectivities ∼ 10 ¹² Jones, and fast response time < 85 ms were realized. These findings present an alternative approach through graphene‐in‐ink formulation, revealing the importance of controlled film formation and paving a unique pathway for improvisation in printed devices.