Red-Emitting SrGa<sub>2</sub>O<sub>4</sub>:Cu<sup>2+</sup>Phosphor with Super-Long Persistent Luminescence

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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.