Calcium vacancy enhanced self-reduction of Ce4+ for single-phase full-spectrum lighting and information encryption

Abstract

Due to the wide and adjustable emission range, Ce3+ is an indispensable luminous center for full spectrum lighting. However, it needs to be sintered at high temperature in a reducing atmosphere, resulting in difficulty to coexisting with other multivalent activated ions (such as Eu3+, Tm3+), which greatly hinders the formation of full spectrum. In this study, a calcium vacancy enhanced self-reduction of Ce4+ is realized in CaNaSb2O6F (CNSOF) host under air atmosphere sintering, through which Ce3+, Tm3+ and Eu3+ coexisting in a single-phase full spectrum phosphor was prepared. Notably, the artificial introduction of a calcium vacancy was designed to verify this self-reduction mechanism. Moreover, the energy transfer kinetics among Tm3+, Ce3+ and Eu3+ were explored. Finally, combined with a 340 nm UV chip, a full spectrum phosphor-converted light-emitting diode (pc-LED) was fabricated, showing a broad emission range from 400 to 750 nm, Commission Internationale de I’Eclairage (CIE) of (0.3485, 0.3673), Ra of 92 and correlated color temperature (CCT) of 4933 K. Utilizing the variation in emission colors of this phosphor under different UV wavelengths, a dual encryption method combining point character code and fluorescent encryption technique is proposed. This work provides an effective path for Ce4+ self-reduction to apply in full spectrum pc-LED and information encryption.