The spectral properties and the NIR photoluminescence of univalent bismuth Bi+ in RbAlCl4, CsAlCl4, RbMgCl3, CsMgCl3, KCdCl3 and RbCdCl3 crystal phases

Polycrystalline samples of Bi-doped triple chlorides RbAlCl4, RbMgCl3, RbCdCl3, CsAlCl4, CsMgCl3, KCdCl3 were prepared by crystallization from the Lewis acidic melts. The broadband long-lived NIR photoluminescence with maxima near 1 μm was observed from all the materials. The most probable source of this emission is bismuth monocation Bi+, which substitutes for the large alkali cations. The relationship between the Bi+ optical properties and the symmetry of crystal field is discussed.