Broadband white-light emission from supramolecular piperazinium-based lead halide perovskites linked by hydrogen bonds

Abstract

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 bonds, 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 modes 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⁻ octahedron was separated by a 1-methylpiperazine dication. (2,5-dmpz)_0.5PbBr₃·2((CH₃)₂SO) contained half a 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 forms a 1D corner-sharing structure and has localized electronic states near the conduction band minimum, which contributes to the high photoluminescence quantum yield and white-light emission.