Red-Emitting SrGa₂O₄:Cu²⁺Phosphor with Super-Long Persistent Luminescence

The red afterglow of current rare-earth-activated long persistent luminescence (LPL) phosphors is largely still less than 6 h, in contrast to the 20 or 30 h long blue- or green-emitting ones, becoming the main obstacle to realize their multiscenario applications in practice. Herein, we report a rare-earth-free red-emitting LPL phosphor SrGa₂O₄:Cu²⁺that can exhibit an afterglow at about 622 nm lasting over 30 h, which can largely match with the luminance of current blue- or green-emitting LPL phosphors. We find that the Cu²⁺ion could be charged by ultraviolet light from 280 to 420 nm, and the emission has a very broad band with a full width at half-maximum of about 150 nm. Combining the thermoluminescence measurement and the first-principles calculation, we find that the O vacancies and the -1 charged Ga vacancies could store the holes and contribute to the LPL of SrGa₂O₄:Cu²⁺. Our results may dramatically promote and expand its potential applications and stimulate the research of the multicolor LPL phosphors in future.