Broadband White-Light Emission from Supramolecular Piperazinium-based Lead Halide Perovskites Linked by Hydrogen Bonds

We demonstrate white-light emission using lead halide perovskites: (pip)2PbBr6 (pip = piperazine), (pip)2Pb4Cl12, (1mpz)2PbBr6 (1mpz = 1-methylpiperazine), and (2,5-dmpz)0.5PbBr3•2((CH3)2SO) (2,5-dmpz = trans-2,5¬-dimethylpiperazine, abbreviated as (2,5-dmpz)0.5PbBr3)), in which the inorganic frameworks were connected by piperazinium dications through hydrogen bond, forming a three-dimensional supramolecular network. From single-crystal X-ray diffraction measurements and Raman spectroscopy, we identified the crystal structures and local environmental vibrational mode in the inorganic framework, finding that (pip)2PbBr6 crystallized in the centrosymmetric orthorhombic space group Pnnm, whereas (pip)2Pb4Cl12 crystallized in the trigonal/rhombohedral space group R3. The zero-dimensional (1mpz)2PbBr6 structure crystallized in the centrosymmetric monoclinic space group P2/n, whereas the [PbBr6]4- octahedral was separated by 1-methylpiperazine dication. The (2,5-dmpz)0.5PbBr3•2((CH3)2SO) contained a half cation, which was completed by inversion symmetry, along with two dimethyl sulfoxide solvent molecules that crystallized in the monoclinic space group P21/c. Among the perovskites, (2,5-dmpz)0.5PbBr3•2((CH3)2SO) exhibited the longest carrier lifetime (42 ns), the lowest band gap (2.34 eV), and the highest photoluminescence quantum yield (58.02%). This is because it is a 1D corner-sharing structure and has the localized electronic states near to the conduction band minimum, which contributes to high photoluminescence quantum yield and white-light emission.