Efficient Near-Infrared Luminescence Based on Double Perovskite CsSnCl.

CsSnCl 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 CsSnCl 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 Te and Er-co-doped CsSnCl 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 Er were achieved in doped CsSnCl compounds for the first time. Moreover, the visible luminescence lifetimes of Te/Er-co-doped CsSnCl decreased with the increase in the Er concentration due to the increasing energy transfer efficiency. The strong and multi-wavelength NIR luminescence of Te/Er-co-doped CsSnCl originates from the 4f→4f transition of Er, which was sensitized by the spin-orbital allowed S→P transition of Te through a self-trapped exciton (STE) state. The findings suggest that ns-metal and lanthanide ion co-doping is a promising method to extend the emission range of CsSnCl materials to the NIR region.