Synthesis and luminescence properties of double perovskite Bi3+/Mn4+ co-doped Ca2GdTaO6 phosphor

Bi3+-doped, Mn4+-doped, and Bi3+/Mn4+ co-doped oxide phosphors Ca2GdTaO6 (CGT) are prepared via the solid-state reaction method. The phase purity and morphology of CGT: Bi3+, Mn4+ phosphors are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The band structure and density of state for CGT are calculated based on density functional theory (DFT). The bandgap of the CGT host is 3.72 eV. The photoluminescence (PL) and photoluminescence excitation (PLE) spectra of CGT: Bi3+ and CGT: Mn4+ is investigated in detail. The overlap between the emission spectra of Bi3+ and the excitation of Mn4+ proves energy transfer from Bi3+ to Mn4+. The corresponding mechanism of the Bi3+ -> Mn4+ energy transfer process is investigated in detail based on the decay time and PL spectra. Energy transfer efficiency is also calculated. Upon excitation at 320 nm, Bi3+/Mn4+ co-doped CGT phosphors show dual emission attributed to the blue-violet emission (429 nm) of P-3(1)<- S-1(0) transition of Bi3+ and red emission (679 nm) of E-2(g)->(4)A(2g) of Mn4+. The intensity of the blue-violet and red emission peaks can be easily adjusted by controlling the concentration of Bi3+ and Mn4+ in the CGT host. The emission band is well-matched with the absorption bands of chlorophylls a and phytochrome PR under the near-ultraviolet to blue excitation, suggesting that the phosphors have great potential applications in light-emitting diodes (LEDs) to modulate plant growth.