Low dimensional organic inorganic metal halide materials
have shown
broadband emission and large Stokes shift, making them widely used
in various fields and a promising candidate material. Here, the zero-dimensional
lead-free bromide single crystals (C6H14N)3Bi2Br9·H2O (1) and (C6H14N)3Sb3Br12 (2) were synthesized. They crystallized in
the monoclinic crystal system with the space group of P21 and P21/n, respectively. Through ultraviolet–visible–near-infrared
(UV–vis–NIR) absorption analysis, the band gaps of (C6H14N)3Bi2Br9·H2O and (C6H14N)3Sb3Br12 are found to be 2.75 and 2.83 eV, respectively. Upon
photoexcitation, (C6H14N)3Bi2Br9·H2O exhibit broad-band red
emission peaking at 640 nm with a large Stokes shift of 180 nm and
a lifetime of 2.94 ns, and the emission spectrum of (C6H14N)3Sb3Br12 are similar
to those of (C6H14N)3Bi2Br9·H2O. This exclusive red emission is
ascribed to the self-trapping exciton transition caused by lattice
distortion, which is confirmed through both experiments and first-principles
calculations. In addition, due to the polar space group structure
and the large spin–orbit coupling (SOC) associated with the
heavy elements of Bi and Br of crystal 1, an obvious
Rashba effect was observed. The discovery of organic inorganic metal
bromide material provides a critical foundation for uncovering the
connection between 0D metal halide materials’ structures and
properties.