Spatially Modulating the Fluorescence Color of Mixed-Halide Perovskite Nanoplatelets through Direct Femtosecond Laser Writing

Lead halide perovskites are widely applied not only in photovoltaics, but also on-chip light sources, and photon detection. In order to promote the incorporation of perovskite into integrated devices, microscale color patterning flexibility is a very important step. Here we demonstrate spatially resolved modulation of the fluorescence of nanoplatelets (NPs) by femtosecond direct laser writing (fs-DLW). As the perovskite NP for fs-DLW pattern is specially designed with a gradual bromide–iodide composition along the depth, under a controlled laser pulse the replacement of iodide ions by bromide ions can be activated and fluorescence is thus modulated from red to green. The effect of processing depth and NP thickness on fluorescence modulation is systemically investigated. The as-grown thick NP (thickness≈500 nm) mainly exhibits 690-nm emission from the bottom iodine rich phase. After halide substitution induced by fs-DLW, a new fluorescence peak appears in the wavelength range of 540 to 600 nm, of which pea...