High‐Security and High‐Efficiency Information Encryption/Decryption Based on Two‐Dimensional Hybrid Organic–Inorganic Perovskites via Delicate Organic‐Cation Engineering

Optical encryption based on stimuli‐responsive luminescence (SRL) materials has received enormous interest in the field of information security. Metal–halide perovskites, as a newly emerging SRL material, have shown great potential for confidential information encryption/decryption (InfoED) applications. However, it is rather challenging to ensure high security and achieve high readout efficiency in perovskite SRL‐based InfoED. Herein, we present a unique InfoED strategy using two‐dimensional hybrid organic–inorganic perovskites via delicate organic‐cation engineering, benefiting from the high contrast and quick response of their photoluminescence behaviors. Indistinguishably encrypted information can be efficiently decrypted through triple‐key implementation (i.e., ultraviolet‐light irradiation, temperature control, and narrow‐bandpass filtering) that operates in multiple switching modes, enabling us to demonstrate extremely high security by adopting dot‐matrix patterning scenarios that are virtually uncrackable. As a proof of principle, a simple 2 × 2 patterning can yield a code dictionary with random variants as high as ~10^{47}, which will take as long as ~10^{22} years to crack using the hitherto fastest supercomputer El Capitan. Our perovskite SRL‐based InfoED strategy provides a promising solution for information security based on optical encryption.