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

Abstract Lanthanide ion (Ln 3+ )‐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 Ln 3+ ‐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 Yb 3+ and Bi 3+ in CsMnCl 3 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 CsMnCl 3 lattice upon co‐doping of Bi 3+ ions, which optimize the energy transfer process between Bi 3+ ‐Mn 2+ ‐Yb 3+ . The PLQY of optimized CsMnCl 3 : Bi 3+ /Yb 3+ NIR emitter reaches 59.8% under UV excitation, which is the highest reported value among Yb 3+ ‐doped lead‐free perovskites. Furthermore, benefiting from the light absorption of Mn 2+ in visible region, the NIR emission of Yb 3+ 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 CsMnCl 3 : Bi 3+ /Yb 3+ perovskite has demonstrated application prospects in versatile photonic fields such as latent fingerprint detection, night vision, and biological imaging.