All‐Inorganic Cs₂YbCl₅·H₂O Perovskite with Luminescence Response to Methanol for Anti‐Counterfeiting

Stimuli‐responsive luminescent materials have attracted much research attention due to their wide application potential in various fields. Typically, the family of hydrated double perovskite A 2 M III X 5 ·H 2 O shows unique emission color transformation between hydrated and dehydrated complexes, highlighting the application potential in advanced anti‐counterfeiting. Herein, two zero‐dimensional perovskites of Cs 2 YbCl 5 ·H 2 O and Cs 3 YbCl 6 , are reported and broad‐band self‐trapped exciton recombination emission can be realized via external Sb 3+ doping. Intriguingly, the Cs 2 YbCl 5 ·H 2 O can be transformed to the dehydrated counterpart of Cs 3 YbCl 6 through a facile methanol treatment at room temperature, leading to the emission color transformation from yellow to green. Notably, the green‐emissive Cs 3 YbCl 6 :Sb 3+ delivers a high photoluminescence quantum yield of 67.3%. Leveraging the advantages of obvious methanol‐induced emission color transformation between Cs 2 YbCl 5 ·H 2 O and Cs 3 YbCl 6 at room temperature, Cs 2 YbCl 5 ·H 2 O can be used in the field of high‐security‐level anti‐counterfeiting.