Simultaneously Achieving Multicolor Emission of Down‐Shifting and Up‐Conversion in Yb3+, Er3+ ‐Codoped Cs2NaGdCl6 Double Perovskites

Abstract

AbstractUltraviolet (UV) excited down‐shifting (DS) double perovskites with broad emission have potential applications in anti‐counterfeiting. However, discovering new materials and achieving multimode luminescence present significant challenges. In this work, a novel double perovskite, Cs2NaGdCl6 is synthesized, with sky‐blue self‐trapped exciton (STE) emission under UV excitation using a solvothermal method. By incorporating Er3+ ions into Cs2NaGdCl6, green DS and green up‐conversion (UC) luminescence are achieved under UV and near‐infrared (NIR) excitation. The addition of the sensitizer Yb3+ ion led to a significant enhancement of 21.5‐fold in DS red luminescence and 7.5‐fold in UC green luminescence. The color of both DS and UC luminescence in Cs2NaGdCl6:Yb3+, Er3+ is further adjusted from green‐dominated to red‐dominated, due to the cross‐relaxation process between Er3+ and Yb3+, Er3+ and Er3+, respectively. The combination of UC and DS luminescence, along with the ability to modulate emission color in rare‐earth‐based materials, opens new possibilities for high security anti‐counterfeiting applications.