Photoluminescence from Bi5(GaCl4)3 molecular crystal

Abstract

Bi₅(GaCl₄)₃ sample has been synthesized through the oxidation of Bi metal by gallium chloride (GaCl₃) salt. Powder X-ray diffraction as well as micro-Raman scattering results revealed that, in addition to crystalline Bi₅(GaCl₄)₃ in the product, an amorphous phase containing [GaCl₄]⁻ and [Ga₂Cl₇]⁻ units also exists. The thorough comparison of steady-state and time-resolved photoluminescent behaviors between the Bi₅(GaCl₄)₃ product and Bi₅(AlCl₄)₃ crystal leads us to conclude that Bi₅³⁺ is the dominant emitter in the product, which gives rise to the ultrabroad emission ranging from 1 to 2.7 μm. Detailed quantum chemistry calculation helps us assign the observed excitations to some electronic transitions of the Bi₅³⁺ polycation, especially at shorter wavelengths. It is believed that our work shown here is not only helpful to solve the confusions on the luminescent origin of bismuth in other material systems, but also serves to develop novel broadband tunable laser materials.