Modulating the Afterglow Time of Mn2+ Doped Metal Halides and Applications in Advanced Optical Information Encryption

Mn2+doped metal halide that can be grown by a facile solution reaction is a promising low-cost afterglow material. However, the afterglow mechanism is still elusive. Using a facile method to modulate afterglow time is still to be explored. In this work, we reveal that the afterglow of Cs2Na0.2Ag0.8InCl6:y%Mn can be significantly modulated by Mn2+concentration. We propose that replacing Ag+with Mn2+leads to the appearance of interstitial Ag+, which temporally store the photogenerated electrons (Ag++e−→Ag). After the removal of excitation, the gradual recombination between residual holes and stored electrons [h++Ag++e−→hν+Ag+] explains the afterglow. However, excessive Mn2+doping at interstitial sites does not bring about more interstitial Ag+but instead introduces nonradiative traps. Therefore, as the Mn2+concentration increases, the afterglow time increases from 350 s to 530 s and then decreases to 230 s, reaching a maximum at y = 40. Thus, a dynamic optical information storage and encryption application is demonstrated based on the modulated afterglow time.