Negative Thermal Quenching of Efficient White-Light Emission in a 1D Ladder-Like Organic/Inorganic Hybrid Material

The synthesis and the optical properties of a new organic–inorganic hybrid material (C₆H₂₂N₄)[Pb₂Br₈] (abbreviated as TETAPb₂Br₈) is reported here. Its ladder-like crystal structure is built up from infinite 1D chains of corner-sharing [Pb₂Br₈]⁴⁻ bi-octahedra surrounded by tetra-protonated triethylenetetramine (abbreviated as TETA⁴⁺) organic cations. Under UV excitation, this hybrid organic–inorganic compound emits white light due to radiative recombinations of self-trapped excitons associated with a structural distortion of the PbBr₆ octahedra. Thin films of TETAPb₂Br₈ show a photoluminescence (PL) quantum yield of ≈11% and exhibit a Commission Internationale de l'Eclairage coordinates of (0.32, 0.37). In the low-temperature range, the PL intensity increases with increasing temperature. This negative thermal quenching of white-light emission is interpreted in terms of transitions between excitonic states involving an exciton–phonon interaction. The interpretations are supported by the temperature dependence of the resonant Raman scattering and by density functional theory calculations.