Efficient and Stable 1550 nm Near-Infrared Emission in Er 3+ –Bi 3+ Codoped Cs 2 SnCl 6 Microcrystals

Although all-inorganic lead-free metal halides exhibit considerable potential for optoelectronic applications, achieving high-performance 1540 nm near-infrared (NIR) emission in these systems is a significant challenge. Herein, we demonstrate a codoping strategy utilizing Bi 3+ and Er 3+ ions to enable enhanced 1540 nm NIR luminescence in vacancy-ordered Cs 2 SnCl 6 double perovskite phosphors compatible with commercial near-ultraviolet LED excitation sources. By leveraging the spin–orbit permitted 1 S 0 → 3 P 1 transition of Bi 3+ as an effective sensitization pathway, we successfully activated the NIR emission band corresponding to the Er 3+ 4 I 13/2 – 4 I 15/2 electronic transition. The optimized phosphor achieved a notable quantum efficiency of 10.3% for the Er 3+ -derived NIR emission. Moreover, the Er 3+ 1540 nm emission exhibits excellent stability over six months, retaining 92.5% of their initial PL intensity. Finally, we fabricated NIR phosphor-converted LEDs based on Bi 3+ - and Er 3+ -codoped Cs 2 SnCl 6 and successfully applied them to night imaging. This work expands the application potential of the Cs 2 SnCl 6 matrix, paving the way for its development as a near-infrared phosphor for advanced optoelectronic applications.