Quantum Dots of [Na4Cs6PbBr4]8+, Water Stable in Zeolite X, Luminesce Sharply in the Green

Nanocrystals (NCs) of CsPbX3, X = Cl, Br, or I, have excellent photoluminescent properties: high quantum yield, tunable emission wavelengths (410-700 nm), and narrow emission band widths. CsPbBr3NCs show high promise as a green-emitting material for use in wide color gamut displays. CsPbBr3NCs have, however, not been commercialized because they are sensitive to moisture and heat. To avoid these problems, this work attempts to introduce CsPbBr(3)into five zeolites. The zeolite X product, Pb,Br,H,Cs,Na-X, shows superior stability toward moisture, maintaining its initial luminescence properties after being under water for more than a month. Its structure, determined using single-crystal X-ray crystallography, shows that quantum dots (QDs) of [Na4Cs6PbBr4](8+)(not of CsPbBr3) have formed. They are tetrahedral PbBr(4)(2-)ions (Pb-Br = 3.091(11) angstrom) surrounded by Na(+)and Cs(+)ions. Each fills the zeolite's supercage with its Pb(2+)ion precisely at the center, a position of high symmetry. The peaks in the emission spectra of Pb,Br,H,Cs,Na-X and the CsPbBr3NCs are both at about 520 nm. The FWHM of Pb,Br,H,Cs,Na-X, however, is narrower than any previously reported for any of the CsPbBr3NCs, and for zeolite Y and the various mesoporous materials treated with CsPbBr3.