The luminescent properties of metal halides are determined by the inorganic framework and solvent molecules

The luminescent properties of metal halides are usually considered to be determined by the inorganic framework. In this work, we propose that the luminescent properties of metal halides are determined by both the inorganic framework and the solvent [Denoted as (inorganic framework + n·solvent molecules), n = 0, 1, 2…] through the abundant solvatochromic or thermochromic effect of tetrabutylammonium lead bromides [TPB, T = TBA (tetrabutylammonium), P = Pb (lead), B = Br (bromide)] containing water (H₂O) and ethanol (EtOH). One-dimensional (1D) TPB can form ligands of [[Pb₅Br₁₈]^8- + 2H₂O_(H)], [[Pb₅Br₁₈]^8- + 2H₂O_(H) + 2H₂O] and [[Pb₅Br₁₈]^8- + 2EtOH] by solvent or heat treatment has completely different luminescent properties resulting from different solvents. They exhibit broad spectral emission due to strong electron-phonon coupling, as do other 1D metal halides. However, the 1D TPB containing only [[Pb₅Br₁₈]^8- achieves extremely rare narrow-band green emission, with full width at half maximum (FWHM) of 21 nm at room temperature and 8 nm at low temperature, color gamut covers 95 % of the International Telecommunication Union recommendation 2020 standard. This work provides new guidance for the modulation of photophysical properties of metal halides, as well as new materials for the display and smart materials fields.