Broadband white-light emission from a novel two-dimensional metal halide assembled by Pb-Cl hendecahedrons

The abundant selection of organic molecules and inorganic units has allowed for the fabrication of organic-inorganic hybrid metal halides (OIMHs) of various morphologies and crystal structures with controllable molecular dimensions and unique photoelectric properties. This work reports a unique two-dimensional (2D) OIMH, C₆H₁₀N₂Pb₂Cl₆, which comprises distinctive lead chloride hendecahedrons, (Pb₂Cl₆)²⁻, and p-phenylenediamium cations. The extremely large lattice distortion endows this 2D OIMH with strong electron-phonon coupling and an abundance of self-trapped excitons (STEs), which contribute to its broadband “cold” white-light emission with a large Stokes shift (∼200 nm) and a remarkable photoluminescence quantum efficiency (PLQE) of over 17% in 2D OIMHs.