Simple purification for highly luminescent MAPbI₃ perovskite quantum dots (PeQDs)

Organic–inorganic lead halide perovskite quantum dots (PeQDs) are promising light source materials for wide color gamut displays because of their excellent optical properties. Green-emitting CH₃NH₃PbBr₃ (MAPbBr₃) obtained by ligand-assisted reprecipitation (LARP) demonstrate superior optical properties such as high photoluminescence quantum yield (PLQY) and high optical stability. However, red-emitting MAPbI₃ by the LARP method remains a great challenge because its PLQY and optical stability are inferior to MAPbBr₃ due to non-luminescent complexes formed by the coordination of polar solvents to iodine defects. Notably, polar solvents used in the LARP strongly collapse the perovskite structure, resulting in the degradation of optical properties. Therefore, the removal of the remaining polar solvents and non-luminescent complexes after the preparation of MAPbI₃ dispersions is essential for their successful practical application. Herein, we report a simple purification method to improve the optical properties and stability of MAPbI₃ dispersions by passing them through a column packed with molecular sieves. They exhibited markedly improved optical properties because the polar solvent was efficiently removed from MAPbI₃ dispersions. The purified MAPbI₃ exhibited a PLQY of 88% with a red PL peak at 619 nm. The PLQY could be maintained at approximately 80% after 14 days of storage with no fluctuation in its PL peak and no expansion of the full widths at half maximum. Thus, this simple purification is a promising method to obtain PeQDs containing iodide with high PLQY, high optical stability, and versatility.