“…36 Actually, trivalent bismuth cations in inorganic compounds exhibit interesting luminescence properties related to their 6s 2 configuration. 37,38 Above 80 K, radiative transitions are mainly assigned to 3 P 1 → 1 S 0 transitions 13,35,37 or charge transfer transitions between oxygen ligands and Bi 3+ ions, 38 giving rise to luminescence spectra peaked in the blue to green region under UV excitation. On the other hand, Bi 2+ ions show PL emission in the range 2.10-1.95 eV under UV excitation.…”