Modulating the Afterglow Time of Mn Doped Metal Halides and Applications in Advanced Optical Information Encryption.

Mn 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 CsNaAgInCl:y%Mn can be significantly modulated by Mn concentration. We propose that replacing Ag with Mn 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 Mn doping at interstitial sites does not bring about more interstitial Ag but instead introduces nonradiative traps. Therefore, as the Mn 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.