Surface Coating of Lead-free Perovskites to Break the Luminescence Threshold for Fluorescent Information Recognition
Hongbo Zhao, Ru Chen, Xiaoyan Li, Lifan Shen, Edwin Yue Bun Pun, Hai Lin
Abstract
Lead-free perovskites are becoming a promising candidate in the new generation of fluorescence information recognition owing to their superior optoelectronic properties and stable chemical properties. However, the vast majority of perovskite phosphors present a luminescence threshold (LT) due to concentration quenching and exhibit a single luminescent peak as the monochrome source, leading to limited application prospects. Herein, surface coating of Bi 3+ -doped all-inorganic lead-free Cs 2 ZrCl 6 perovskite microcrystal is designed to break LT and present dual-mode luminescence under 259 and 358 nm excitation. Dual-mode fluorescence peaks are located at 435 and 453 nm, contrary to self-trapped exciton (STE) emissions reported previously, which originate from STE emission and inter-configurational 3 P 0,1 → 1 S 0 transitions of Bi 3+, respectively. Moreover, surface coating of ethyl orthosilicate (CHSiO) is introduced to form a core–shell structure, enhancing the particle dispersion and the luminescence stability of Cs 2 ZrCl 6:Bi 3+ phosphors, which breaks the LT to increase luminescence intensity. Finally, the Cs 2 ZrCl 6:Bi 3+ -coated CHSiO is mixed with polydimethylsiloxane and printed QR code by screen printing technology to achieve dual-mode luminescence and display. These findings reveal the unique advantages of surface-coated Bi 3+ -doped Cs 2 ZrCl 6 perovskites, thus opening a new pathway for multi-mode fluorescence recognition and remote excitation applications.