Luminescence enhancement and energy transfers of Ce3+ and Sm3+ in CaSrSiO4 phosphor

Abstract

Orthosilicate phosphors with desirable properties are used as commercial materials in the fields of lighting and display. Herein, a series of Ce³⁺ and Sm³⁺ singly- or doubly-doped CaSrSiO₄ phosphors with charge compensations by co-doping of Na⁺ ions were successfully prepared using a conventional solid-state method and their crystal structures were determined from XRD profiles and refinement with the Rietveld method. Emphatically, Ce³⁺ or Sm³⁺ singly-doped CaSrSiO₄ phosphors exhibited good photoluminescence properties. In doubly-doped phosphors, the red emission of Sm³⁺ was enhanced by energy transfer (ET) from Ce³⁺ to Sm³⁺ ions. The mechanism of ET was deduced to be dipole–dipole interaction using the Inokuti–Hirayama (I–H) model. The red emission intensity of Ca_0.97Sr_0.97Ce_0.01Sm_0.02Na_0.03SiO₄ at 425 K was 85.21% of that at 300 K, indicating satisfactory thermal stability of fluorescence. The obtained white LED device fabricated with Ca_0.97Sr_0.97Ce_0.01Sm_0.02Na_0.03SiO₄ phosphor, Sr₂SiO₄:Eu²⁺ and an ultraviolet (UV) chip displayed a bright white light with CIE chromaticity coordinates (0.32, 0.38), correlated colour temperature (CCT) of 6056 K and colour rendering index (R_a) of 73.5.