Highly Efficient Near‐Infrared Luminescence in Bi³⁺‐Yb³⁺ Co‐Doped CsMnCl₃ Perovskite Single Crystals for Versatile Photonic Applications

Abstract Lanthanide ion (Ln³⁺)‐doped lead‐free perovskites with near‐infrared (NIR) luminescence have promising application prospects in environmentally friendly photonic devices. It remains a challenge to enhance the photoluminescence quantum yield (PLQY) of Ln³⁺‐doped lead‐free perovskites due to their poor light absorption and low energy transfer efficiency. Herein, highly efficient NIR emission is achieved through co‐doping Yb³⁺ and Bi³⁺ in CsMnCl₃ perovskites. Theoretical and experimental results demonstrated that the highly efficient NIR emission is attributed to additional intense light absorptions at 330 nm and local symmetry breaking of CsMnCl₃ lattice upon co‐doping of Bi³⁺ ions, which optimize the energy transfer process between Bi³⁺‐Mn²⁺‐Yb³⁺. The PLQY of optimized CsMnCl₃: Bi³⁺/Yb³⁺ NIR emitter reaches 59.8% under UV excitation, which is the highest reported value among Yb³⁺‐doped lead‐free perovskites. Furthermore, benefiting from the light absorption of Mn²⁺ in visible region, the NIR emission of Yb³⁺ can also be excited using low‐energy light sources, providing a general strategy to unlock the low‐energy light excitable NIR emitters. Based on its excellent luminescent properties, the CsMnCl₃: Bi³⁺/Yb³⁺ perovskite has demonstrated application prospects in versatile photonic fields such as latent fingerprint detection, night vision, and biological imaging.