Synthesis And Multi-color Luminescence Properties Of Metal Halide Perovskite Alloyed Nanostructures

Perovskite materials are considered to be suitable for solar cells,nanoscale lasers,photodetectors,and light-emitting diodes due to their excellent optoelectronic properties,including tunable bandgaps,high quantum efficiency,and long carrier diffusion length et.al.We first use the traditional chemical vapor deposition method to achieve pure composition,high crystalline cesium lead halide perovskite crystals.The perovskite micro/nano structures with different morphology were realized by changing the growth conditions,including perovskite micro-crystal and perovskite nanorods.The alloyed halide perovskite nanocrystals are achieved by a two-step growth process.These as-grown Cs Pb I_3xBr_3-3x（X=0.2）perovskite alloy nanocrystals show dual-wavelength emissions under a focused laser illumination.Under a 375-nm laser illumination,theμ-PL emission spectra of the alloy nanocrystals exhibit two emission bands at 570 nm and 690 nm,respectively,which show gradually raised and decreased PL intensity during the laser illumination.Moreover,the time-dependent emission wavelength of the two bands almost has no changes,while the emission intensity of the two bands shows periodic fluctuation with the switch of excitation light.This tunable emission of perovskite nanocrystals may suggest that phase segregation occurs during laser illumination.These results may have potential applications in tunable nanophotonic devices and multi-color displays.Here,we report a magnetically controlled source-moving chemical vapor deposition approach for the spatial bandgap engineering of cesium lead halide perovskites(Cs Pb Cl_3（1-x）Br_3x,X=0～0.84)alloy microstructures on a photonic chips.Owing to the temperature-selected effect along the deposition zoon,cesium lead halide perovskites Cs Pb Cl_3（1-x）Br_3x microcrystals with engineerable bandgaps from 2.42 to 2.91 e V are obtained.Along the length of these achieved transparent photonic chips,the composition can be continuously tuned from X=0（Cs Pb Cl₃）on one side to X=0.84(Cs Pb Cl_0.48Br_2.52)on the other side.The emission light modulated gradually from blue（425 nm）to green（512 nm）under a320 nm laser illumination.Furthermore,these perovskite structures based on transparent photonic chips show stable emission with no measurable degradation after 24 hours under a continuous wavelength（CW）320 nm laser illumination.We used the same method to achieve mixed perovskite(Cs Pb I_3xBr_3-3x,X=0.1～0.35)on a single substrate.The Cs Pb I_3xBr_3-3xmicrocrystals were synthesized by a source-moving chemical vapor deposition（CVD）method,and the emission light was gradually modulated from green（558 nm）to orange-red（610 nm）under a 375-nm continuous laser irradiation.In the future,these bandgap graded microstructures demonstrated here may find potential applications in multicolor displays,solid-state light emitters,and broadband light sources.