Efficient Near-Infrared Luminescence Based on Double Perovskite Cs₂SnCl₆

Cs₂SnCl₆ double perovskite has attracted wide attention as a promising optoelectronic material because of its better stability and lower toxicity than its lead counterparts. However, pure Cs₂SnCl₆ demonstrates quite poor optical properties, which usually calls for active element doping to realize efficient luminescence. Herein, a facile co-precipitation method was used to synthesize Te⁴⁺ and Er³⁺-co-doped Cs₂SnCl₆ microcrystals. The prepared microcrystals were polyhedral, with a size distribution around 1-3 μm. Highly efficient NIR emissions at 1540 nm and 1562 nm due to Er³⁺ were achieved in doped Cs₂SnCl₆ compounds for the first time. Moreover, the visible luminescence lifetimes of Te⁴⁺/Er³⁺-co-doped Cs₂SnCl₆ decreased with the increase in the Er³⁺ concentration due to the increasing energy transfer efficiency. The strong and multi-wavelength NIR luminescence of Te⁴⁺/Er³⁺-co-doped Cs₂SnCl₆ originates from the 4f→4f transition of Er³⁺, which was sensitized by the spin-orbital allowed ¹S₀→³P₁ transition of Te⁴⁺ through a self-trapped exciton (STE) state. The findings suggest that ns²-metal and lanthanide ion co-doping is a promising method to extend the emission range of Cs₂SnCl₆ materials to the NIR region.