Luminescence Patterns\non Multimillimeter Single-Crystal\nMAPbBr<sub>3</sub> Microplatelets via Thermal Ablation Effects

The single crystal distinguishes itself as the most outstanding\nrepresentative of excellent\noptoelectronic performance among perovskite semiconductors due to\nits exceptional charge carrier properties, extraordinary optophysics,\nprecise structural geometries, and superior material stabilities.\nHowever, it exhibits mediocre performance in light emission, which\ncan be attributed to its excessive carrier diffusion lengths and extremely\nlow recombination rates. To address this challenge, this study puts\nforward a controllable high-temperature annealing treatment strategy\nconcentrating on multimillimeter-scale MAPbBr<sub>3</sub> micrometer-thick\nplatelet single crystals (MPSCs). Through the utilization of thermal\nablation effects to convert the surface monocrystalline lattices into\npolycrystalline perovskite nanocrystals (PNCs) with a remarkably increased\nspecific surface area, the fluorescence intensity arising from the\nrapid recombination of free carriers on the PNC surface is enhanced\nby 320 times compared to the pristine MPSC surface. These PNCs produced\nthrough surface annealing, with the characteristic of loose adhesion\nto surfaces, can be mechanically wiped away and regenerated in situ\nvia reannealing the residual MAPbBr<sub>3</sub> MPSCs, guaranteeing\nhigh intensity, durability, and standard geometric fluorescence. Moreover,\nby regulating the surface distributions of thermal ablation effects\nand carrying out embossing annealing treatment or laser direct writing,\nwe can design and fabricate relatively complex, high-contrast (255×),\nand clearly resolved fluorescence patterns on MPSC surfaces.