Structural and optical properties of Dy~(3+):YAlO_3 phosphors for yellow light-emitting diode applications

The spectroscopic properties of a series of Dy³⁺ single-doped and Dy³⁺/Nd³⁺, Dy³⁺/Tb³⁺, and Dy³⁺/Tm³⁺ co-doped YAlO₃ (yttrium aluminum perovskite, YAP) phosphors were investigated and compared through the measurements of optical absorption, emission spectra, and fluorescence decay curves. For the Dy³⁺ ion single-doped samples, the intensity of each absorption band increases with an increment in Dy³⁺ ion doping concentration, and the identified strong absorption peak at 447 nm indicates that Dy³⁺:YAP phosphors are suitable to be pumped by a blue laser diode (LD). For all co-doped samples, absorption peaks of Dy³⁺ ion along with some of the absorption bands of Nd³⁺, Tb³⁺, and Tm³⁺ ions are observed. Under 351 and 447 nm excitation, a prominent emission peak at 572 nm was obtained in all the samples, corresponding to Dy³⁺: ⁴F_9/2 → ⁶H_13/2 transition. Here, 2 at% Dy³⁺:YAP phosphor exhibits the highest yellow emission intensity under 447 nm pumping. Among the three kinds of Dy³⁺ co-doped phosphors, Dy³⁺/Tb³⁺:YAP phosphor possesses the dominant yellow emission. The fluorescence decay curves show exponential behaviour and are fitted well. The Commission International de L'Eclairage (CIE) chromaticity coordinates were calculated following the respective emission spectra, and it is found that all the coordinates locate in the yellow region. The energy transfer (ET) processes were investigated and the concentration quenching mechanism was discussed. The obtained results suggest that Dy³⁺-activated YAP phosphors are good candidates for yellow LED applications.