Mn 2+ /Er 3+ ‐Codoped Cs 2 AgInCl 6 Double Perovskites with Dual Emission and Photochromism Properties for Anti‐Counterfeiting Application

Highly transparent inorganic photochromic materials have several promising applications, especially for anti‐counterfeiting application. Enriching and enhancing the luminescent properties of perovskite by doping transition metals and rare earth elements into the host is a feasible and attractive route. Codoping of Mn 2+ and Er 3+ can realize novel anti‐counterfeiting properties with upconversion emission and photochromic ability within a double perovskite structure of Cs 2 AgInCl 6 .The Cs 2 AgInCl 6 : Mn 2+ , Er 3+ single crystal can be observed in a reversible color variation from yellow to dark violet by implementing under 365, 520 nm illumination or thermal treatment. In addition, the crystal emits red and green light under the excitation of 365 nm ultraviolet and 980 nm laser, respectively. The introduction of Mn 2+ endowed Cs 2 AgInCl 6 with photochromic ability, and Mn 2+ acted as a bridge for energy transfer from host excitons to Er 3+ , facilitating emission in the visible region. Er 3+ achieve upconversion luminescence in the material through its abundant energy levels and acting synergistically with Mn 2+ . Herein, the Cs 2 AgInCl 6 :Mn 2+ , Er 3+ combines various optical properties and has applications for specific anti‐counterfeiting demands.