Near-infrared downshifting luminescence of Ca₂LaTaO₆:Nd³⁺/Yb³⁺/K⁺ phosphors and their applications: solar cells and anti-counterfeiting

A series of Nd³⁺/Yb³⁺ co-doped Ca₂LaTaO₆ (CLTO) phosphors are synthesized by a high temperature solid phase method. Structural characterization confirms the successful incorporation of Nd³⁺ and Yb³⁺ ions into the CLTO host lattice. The photoluminescence excitation (PLE) spectra and photoluminescence (PL) spectra of CLTO:Nd³⁺ and CLTO:Nd³⁺/Yb³⁺ are investigated in detail. Under the excitation of ultraviolet (UV) and visible (VIS) light, the CLTO:Nd³⁺/Yb³⁺ phosphor emits broadband near infrared (NIR) luminescence. In particular, the luminescence intensity of the Yb³⁺ ion is increased through an energy transfer (ET) process from Nd³⁺ to Yb³⁺. The luminescence mechanism of the CLTO:Nd³⁺/Yb³⁺ sample is analyzed based on the decay lifetime and PL spectra. In addition, the NIR emission intensity of Yb³⁺ ions is also enhanced by doping K⁺ ions. The broadband luminescence (850-1050 nm) of the CLTO:Nd³⁺/Yb³⁺/K⁺ phosphor has good application in solar cells and anti-counterfeiting.