Highly efficient Eu3+-activated Ca2Gd8Si6O26 red-emitting phosphors: A bifunctional platform towards white light-emitting diode and ratiometric optical thermometer applications

Abstract

To fulfill bifunctional applications of the white light-emitting diode (white-LED) and optical thermometry, Eu3+-activated Ca2Gd8Si6O26 phosphors were prepared. Upon 394 nm excitation, dazzling red emission with admirable color purity of 93.8% was seen and the optimal doping content of the Eu3+ ions in the Ca2Gd8Si6O26 host was 30 mol%. The Ca2Gd8Si6O26:2.4Eu3+ phosphors showed a high quantum efficiency of 53.9%. Via investigation of the relation between the dopant content and emission intensity, one knows that the concentration quenching mechanism was decided by electric dipole-dipole interaction. Though estimating the values of Ω2 and Ω4 based on the Judd-Ofelt theory, it was proved that the Eu3+ ions took the low symmetry sites in the Ca2Gd8Si6O26 host lattices. Furthermore, the temperature-dependent emission spectra manifested that the resultant compounds had splendid thermal stability with activation energy of 0.25 eV. Utilizing the prepared compounds as the red-emitting components, a white-LED was packaged and it can emit high quality white light with high color rendering index (84.8) and low correlated color temperature (4981 K). Additionally, through analyzing the temperature-dependent excitation spectrum, the optical thermometric behaviors of the designed phosphors were studied. The maximum absolute and relative sensitivities of the studied compounds were 0.0014 K-1 and 0.276% K−1, respectively. These results provided a new insight into searching for novel bifunctional luminescent materials towards white-LED and ratiometric optical thermometer applications.