Visible to Near‐Infrared Luminescence and Reversible Photochromism in Mn 2+ /Nd 3+ Co‐Doped Double Perovskite for Versatile Applications

Abstract Multifunctional optical materials with temperature sensing and anti‐counterfeiting properties play an essential role in the commercial applications. Herein, Mn 2+ /Nd 3+ co‐doped Cs 2 AgInCl 6 (CAIC) lead‐free double perovskites (DPs) is synthesized through a hydrothermal method, which exhibits visible to near‐infrared (NIR) luminescence and reversible photochromic properties from yellowish to dark purple. The mechanism investigations on the photoluminescence and photochromic phenomena reveal that the incorporation of Mn 2+ ions not only acts as an intermediary in the energy transfer process from the host exciton to Nd 3+ ions, but also plays a pivotal role in the reversible photochromic response. The temperature‐dependent luminescence, attributed to the contrasting thermal responses of Mn 2+ and Nd 3+ ions, enables precise temperature sensing via the fluorescence intensity ratio method. In addition, the integration of visible red emission, NIR luminescence, and photochromic properties in a single CAIC: Mn 2+ /Nd 3+ DPs, offers a multilevel anti‐counterfeiting strategy. The multifunctional CAIC: Mn 2+ /Nd 3+ DPs would open up new avenues for advanced optical applications, particularly in the realms of temperature sensing and security anti‐counterfeiting.