Oriented Perovskite Film from Laser Recrystallization in Magnetic Field

The orientation of crystals on the substrate and the presence of defects are critical factors in electro‐optic performance. However, technical approaches to guide the orientational crystallization of electro‐optical thin films remain challenging. Here, a novel physical method called magnetic‐field‐assisted pulse laser annealing (MAPLA) for controlling the orientation of perovskite crystals on substrates is reported. By inducing laser recrystallization of perovskite crystals under a magnetic field and with magnetic nanoparticles, the optical and magnetic fields are found to guide the orientational gathering of perovskite units into nanoclusters, resulting in perovskite crystals with preferred lattice orientation in (110) and (220) perpendicular to the substrate. The perovskite crystals obtained by MAPLA exhibit significantly larger grain size and fewer defects compared to those from pulsed laser annealing (PLA) and traditional thermal annealing, resulting in improved carrier lifetime and mobility. Furthermore, MAPLA demonstrates enhanced device performance, increasing responsivity and detectivity by two times, and photocurrent by nearly three orders compared with PLA. The introduction of Fe2O3 nanoparticles during MAPLA not only improves crystal size and orientation but also significantly enhances long‐term stability by preventing Pb2+ reduction. The MAPLA method has great potential for fabricating many electro‐optical thin films with desired device properties and stability. “MAPLA” employs magnetic‐field‐assisted pulse laser annealing to control perovskite crystal orientation on substrates, enhancing crystal size, orientation, and stability. Magnetic nanoparticles guide orientational gathering into nanoclusters. Device performance improves with responsivity and detectivity increasing two times, and photocurrent three orders higher than pulsed laser annealing. MAPLA enhances stability by preventing Pb2+ reduction, making MAPLA promising for stable electro‐optical thin films.