Multicolor and multimode luminescent modulation via energy transfer engineering in Tb3+/Eu3+ co-doped (K0.5Na0.5)NbO3 transparent photochromic materials

Abstract

Rare earth doped photochromic materials reveal great potential applications in optical memory storage devices due to their excellent reversible luminescence modulation behavior. Nevertheless, the unicolor emission and unimode luminescence modulation in photochromic materials by singly doped rare earth ions difficultly realize the effective optical data readout, then restricting their practical applications in display technology and multifunctional optical devices. Here, the multicolor and multimode luminescent modulation based on photochromic reactions were successfully obtained in Tb3+/Eu3+ co-doped (K0.5Na0.5)NbO3 system, utilizing the energy transfer engineering. The obtained samples exhibit excellent optical transparent (48% in visible light region and 61% in IR region) and multicolor emission from green, yellow-green, yellow, orange to red. After light irradiation, the emission intensity at 546 nm (green emission) and 612 nm (red emission) decreased significantly. The maximum luminescence switching contrast reach up to 68.93% (ΔRIgreen) of x = 0.004, and 69.77% (ΔRIred) of x = 0.016, respectively. The luminescence modulation ratio shows strong dependence on excitation wavelength and Eu contents, and optical transparent can also realize an effective reversible modulation based on photochromic reaction. The energy transfer from Tb3+ to Eu3+ forming two luminescent centers, then part of the energy is absorbed by color centers, which is the source of the multicolor emission and multimode luminescent modulation. These results may provide a new insight for designing multifunction transparent optical storage devices.