Lead halide perovskites (LHPs) are promising photonic materials. They show excellent performance in LEDs and solar cells due to several properties, including long carrier lifetime, long diffusion lengths, high refractive index, and defect tolerance. LHPs microcrystals, as opposed to single- or poly-crystalline LHPs thin films, have shown great potential for LEDs and lasers. Some have realized as high as 20.7% external quantum efficiency in LED devices. LHPs microplates and nanowires are also efficient, narrowband laser sources at room temperature.
The most significant challenges in LHPs synthesis arise from the fact that LHPs are easily disintegrated in almost any polar solvent due to low lattice formation energy. This limitation precludes various polar chemistries for functionalization and surface coating from being applied to LHPs. Recently, a number of synthetic methods to produce single crystalline LHPs in polar solvents have been reported; however, these methods are limited by slow reaction rate, lack of stoichiometric control, undesirable cracks generated on microcrystals during film detachment, and failure to translate to mass production. This invention generates a new method of crystalline and core-shell LHP synthesis. It utilizes sonochemistry to enable the rapid, large-scale synthesis of various LHPs microstructures in polar aprotic solvents. Such colloidal synthesis enables the full encapsulation of individual LHP microcrystals with polar prepolymers like poly-norepinephrine (pNE). These prepared core-shell structures also show improved optical and structural properties and have functionalizable surfaces.
This invention uses ultrasonication to create a burst of nucleation to overcome the activation barriers of LHPs crystallization and produces high-quality micro- and sub-micron LHPs crystals and dual-phase LHPs nanocrystals in non-perovskite matrices. The process is well suited for the rapid and large-scale fabrication of LHP microcrystals (e.g. 10 billion particles/L). LHPs crystallization is facilitated by several minutes of ultrasonication at room temperature using a bath- or tip-type ultrasonicator. The reaction is completed within 2-15 mins. Single- and dual-phase microparticles with a variety of morphologies can be generated depending on the amount of precursors, their concentration ratios, and the presence of non-ionic surfactants. The ultrasonication method can improve the luminescent properties and structural stability of LHP microcrystals by enabling in-situ coating with polar prepolymers like pNE. Coating with polar prepolymers then enables the functionalization LHPs particles with various polar materials, including plasmonic nanoparticles.
- Fast reaction time (2-15 mins) at room temperature for the first time in polar solvent
- Rapid and large-scale fabrication of LHP microcrystals (e.g. 10 billion particles/L)
- Sonochemically-coated LHPs crystals are functionalizable with polar materials
- Efficient lasing from single CsPbBr3 particles with sizes as small as 2µm (3-5 smaller than the smallest length of LHP lasers demonstrated to date)