Investigation on structure and optical properties of down-conversion aluminosilicate phosphors CaAl2Si2O8: Ce/Tb/Yb

A series of Ce3+, Tb3+ and Yb3+ tri-doped feldspar CaAl2Si2O8 (CASO) phosphors have been successfully synthesized at ∼ 1350 °C under reducing atmosphere. Optical properties of these phosphors have been investigated as a function of doping concentrations by using fluorescence spectra and decay lifetime analysis in detail. The XRD patterns and structure refinements indicate that the dopants do not change the phase structure of host lattice. For Ce3+/Tb3+/Yb3+ all occupied at Ca2+ sites, charge compensation requires cationic vacancies ( V C a / / ) to maintain electrical neutrality instead of oxygen at interstitial site ( O i 2 − ) because the phosphors were synthesized under reducing atmosphere. The near ultraviolet (n-UV) converted to near-infrared (NIR) emission of the aluminosilicate phosphors have achieved via Ce3+ → Tb3+ → Yb3+ resonant energy transfer (ET), enabling their potential application as down-conversion (DC) converter in Si-based solar cells. The role of Tb3+ is acting as ET bridge to connect Ce3+ and Yb3+ ion pairs. Through adjusting optimal doping concentrations, these NIR DC phosphors can exhibit excitation bands in n-UV region and strong NIR emissions.