Multicolor tunable emission through energy transfer in Dy 3+ /Ho 3+ co-doped CaTiO 3 phosphors with high thermal stability for solid state lighting applications

The exploration of multicolor emitting phosphors with single phase is extremely important for n-UV chip excited LED/WLED’s and multicolor display devices. In this paper, Dy 3+ , Ho 3+ singly doped and Dy 3+ /Ho 3+ co-doped CaTiO 3 phosphor materials have been synthesized by solid state reaction method at 1473 K. The synthesized materials were characterized by XRD, FE-SEM, EDX, FTIR, PL and lifetime measurements. The PL emission spectra of Dy 3+ doped CaTiO 3 phosphors give intense blue and yellow emissions under UV excitation, while the PL emission spectra of Ho 3+ doped CaTiO 3 phosphor show intense green emission under UV/blue excitations. Further, to get the multicolor emission including white light, Dy 3+ and Ho 3+ were co-doped simultaneously in CaTiO 3 host. It is found that alongwith colored and white light emissions, it also shows energy transfer from Dy 3+ to Ho 3+ with 367 nm and from Ho 3+ to Dy 3+ under 362 nm excitations. The energy transfer efficiency is found to be 67.76% and 69.39% for CaTiO 3 :4Dy 3+ /3Ho 3+ and CaTiO 3 :3Ho 3+ /5Dy 3+ phosphors, respectively. The CIE color coordinates, CCT and color purity of the phosphors have been calculated, which show color tunability from whitish to deep green via greenish yellow color. The lifetime of 4 F 9/2 level of Dy 3+ ion and 5 S 2 level of Ho 3+ ion is decreased in presence of Ho 3+ and Dy 3+ ions, respectively. This is due to energy transfer from Dy 3+ to Ho 3+ ions and vice versa. A temperature dependent photoluminescence studied of CaTiO 3 :4Dy 3+ /2Ho 3+ phosphor show a high thermal stability (82% at 423 K of initial temperature 303 K) in the temperature range 303–483 K with activation energy 0.17 eV. The PLQY are 30%, 33% and 35% for CaTiO 3 :4Dy 3+ , CaTiO 3 :4Dy 3+ /2Ho 3+ and CaTiO 3 :3Ho 3+ phosphors, respectively. Hence, Dy 3+ , Ho 3+ singly doped and Dy 3+ /Ho 3+ co-doped CaTiO 3 phosphor materials can be used in the field of single matrix perovskite color tunable phosphors which may be used in multicolor display devices, n-UV chip excited LED/WLED’s and photodynamic therapy for the cancer treatment.