Luminescence of Er³⁺ doped double lead halide crystals under X-ray, UV, VIS and IR excitation

Er³⁺ doped double lead halide crystals incorporate a number of properties making them interesting for practical use in light conducting materials. X-ray excited luminescence (XRL) spectra, photoluminescence (PL) spectra in region of 1.5-3.5 eV, photoluminescence excitation (PLE) spectra (2.75-5 eV) and anti-stokes luminescence (ASL) spectra were measured at room temperature in KPb₂Cl₅ (KPC) and RbPb₂Br₅ (RPB) matrices doped with Er³⁺ (1%) ions and in KPC doped with Er³⁺⁺ Yb³⁺ ions(1:3 ratio concentration). Intraconfigurational f→f transitions are observed in Er³⁺ ions in most of the cases. The concrete spectrum form is strongly dependent on the excitation energy. Under 980 nm excitation upper Er³⁺ levels are excited, showing upconversional processes. In case of 313 nm (UV) and 365 nm (VIS) excitation self trapped exciton luminescence was detected in RPB crystal. Additional Yb³⁺ doping ions strongly increase quantum yield under 980 nm excitation and this doping cause insignificant influence on quantum yield under VIS or UV excitation.