Facile Synthesis of Colloidal Lead Halide Perovskite Nanoplatelets via Ligand-Assisted Reprecipitation

This protocol demonstrates the room temperature synthesis of colloidal perovskite nanoplatelets for future optoelectronic applications. The main advantage of this approach is the compositional flexibility it provides. By making straightforward changes to the precursor mixtures, different perovskite nanoplatelets can be easily obtained.

Lead halide perovskites are uniquely suited to the ligand-assisted reprecipitation method. Unlike traditional semiconductors, the bonds within the perovskite crystal lattice can be easily broken and reformed at room temperature. To synthesize and equals to methylammonium lead bromide nanoplatelets, mix individual one milliliter volumes of the indicated 0.2 molar precursor solutions according to the table.

To synthesize and equals to methylammonium lead iodide nanoplatelets, mix individual one milliliter volumes of the indicated 0.2 molar precursor solutions according to the table. To synthesize nanoplatelets with mixed halide compositions, combine bromide only and iodide only perovskite nanoplatelet precursor solutions of the same thickness at the desired volumetric ratio for the target composition. For perovskite nanoplatelet synthesis, inject 10 microliters of each mixed precursor solution into individual 10 milliliter aliquots of toluene under vigorous stirring.

Leave the solutions under stirring for 10 minutes until no further color changes are observed to ensure a complete crystallization of each of the perovskite nanoplatelets. For general purification of the perovskite nanoplatelets, centrifuge the solutions at 2, 050 times g for 10 minutes and discard the supernatants. Then, re-disburse the nanoplatelets in an appropriate volume of solvent according to the planned downstream analysis with vortexing.

Pictures of colloidal perovskite nanoplatelet solutions under ambient and ultraviolet light combined with photoluminescence and absorption spectra further confirm the emissive and absorptive nature of the nanoplatelets. Transmission electron microscopy images and X-ray defraction patterns can be used to estimate the lateral dimensions and stacking spacings of the nanoplatelets, respectively, while also confirming their two-dimensional structures. Absorption spectra of perovskite nanoplatelet solutions with mixed halides demonstrate the tunability of the band gap.

Identical photoluminescence spectra from perovskite nanoplatelets with different ligands demonstrate the compositional flexibility of the organic surface capping species. It must be noted that the precise control of the ratios between individual precursors determines the thickness of the resulting nanoplatelets and ensures their thickness homogeneity. Following the synthesis and purification of the nanoplatelets, post-synthesis processes, such as thin film deposition, polymer encapsulation, and optoelectronic device fabrication can be performed depending on the planned usage.

One exciting feature of this synthetic method is its suitability for automated and high through-put experimentation, which can be used to quickly generate large data sets to train predictive computer models. Lead halides are believed to be carcinogenic and the inhalation of organic solvents and nanoparticles can be dangerous. Handle all of the chemicals in a well contained environment.