Multilevel luminescence of Er3+/Pr3+ co-doped Ca2Nb2O7 ceramics and composite films for optical anti-counterfeiting

Luminescence color and application environment of anti-counterfeiting materials are closely related to the excitation modes, which play a decisive role in information security. Ca1.997-xNb2O7:xEr3+/0.003Pr3+ (x = 0.002, 0.006, 0.01, 0.015, 0.02) ferroelectric ceramics have been prepared via traditional solid-state reaction method. Four-modal luminescence comprising color-tunable (red/yellow/green) photoluminescence (PL), up-conversion luminescence (UCL), photostimulated luminescence (PSL) and thermoluminescence (TL) have been realized in the prepared ceramics. The corresponding mechanisms were also discussed and proposed. PSL using near infrared (NIR) light excitation was first reported in this material. Besides, the as-synthesized phosphors and commercial ZnS:Cu2+ were incorporated into a polydimethylsiloxane (PDMS) matrix to fabricate a multifunctional optical device. The obtained device successfully provides multidimensional codes with colorful (red/pink/white/cyan/green/blue) and multimodal (upconverted/downshifted and photon-/thermo-/mechano-drived) emission, showing the promising prospects in optical information storage and anti-counterfeiting.