Advanced Optical Information Encryption Enabled by Polychromatic and Stimuli‐Responsive Luminescence of Sb‐Doped Double Perovskites

Abstract The smart materials with multi‐color and stimuli‐responsive luminescence are very promising for next generation of optical information encryption and anti‐counterfeiting, but these materials are still scarce. Herein, a multi‐level information encryption strategy is developed based on the polychromatic emission of Sb‐doped double perovskite powders (SDPPs). Cs2NaInCl6:Sb, Cs2KInCl6:Sb, and Cs2AgInCl6:Sb synthesized through coprecipitation methods exhibit broadband emissions with bright blue, cyan, and orange colors, respectively. The information transmitted by specific SDPP is encrypted when different SDPPs are mixed. The confidential information can be decrypted by selecting the corresponding narrowband filter. Then, an encrypted quick response (QR) code with improved security is demonstrated based on this multi‐channel selection strategy. Moreover, the three types of SDPPs exhibit three different water‐triggered luminescence switching behaviors. The confidential information represented by Cs2NaInCl6:Sb can be erased/recovered through a simple water spray/drying. Whereas, the information collected from the green channel is permanently erased by moisture, which fundamentally avoids information leakage. Therefore, different encryption schemes can be designed to meet a variety of encryption requirements. The multicolor and stimuli‐responsive luminescence greatly enrich the flexibility of optical information encryption, which leaps the level of security and confidentiality.

. Higher Sb 3+ doping concentration leads to a decrease in PL efficiency, which may be caused by a nonradiative recombination center from doping-induced defects[Adv.

Figure
Figure S7.PL intensity of Cs2NaInCl6:Sb (a), Cs2KInCl6:Sb (b), Cs2AgInCl6:Sb (c) under continuous irradiation.The PL intensity was monitored under 365 nm UV lamp with a power of 5W.

Figure S9 .
Figure S9.Pattern of a lattice formed by the SDPPs after storage for 0 (a), and 180 days (b), optical channels were selected at 410 nm, 365 nm and 254 nm narrowband filter.

Figure S10 .
Figure S10.Pattern of a QR code formed by the SDPPs after storage for 0 (a), and 180 days (b).After storage in the ambient environment for 180 days, the PL intensities of the SDPPs almost keep constant, indicating the outstanding long-term stability with the encapsulation.

Figure S11 .
Figure S11.Humidification induced PL variation of Cs2KInCl6:Sb.The PL spectra were continuously recorded at a time interval of one minute after the spray treatment.

Figure S18 .Figure
Figure S18.Comparison of XRD patterns of the Cs2KInCl6:Sb and (Cs/K)2InCl5(H2O):Sb.Compared to Cs2KInCl6:Sb, the XRD peak of the (Cs/K)2InCl5(H2O):Sb shifted and showed more bimodal peaks, due to the decrease in symmetry.

Table S1 .
Fitting details for the time-resolved PL decay curves.