Doping lanthanides towards improvement in self-trapped excitons emission and multiple emission color of Cs2KInCl6 double perovskites

Lead-free double perovskites (DPs), characterized by their low toxicity, broad emission spectra and excellent stability, have emerged as highly promising doped hosts with significant potential for visible light applications. However, achieving rich and distinctive multiple photoluminescent (PL) emission through doping with various lanthanide (Ln 3+ ) ions remains a formidable challenge. In this work, we explored the luminescent properties of Cs 2 KInCl 6 , which exhibits intrinsic broad self-trapped excitons (STEs) emission centered at 500 nm. By doping Ln 3+ ions (Dy 3+ , Sm 3+ , and Tb 3+ ) into Cs 2 KInCl 6 , multiple emission could be realized, along with energy transfer (ET) from the intrinsic STEs to Tb 3+ and Sm 3+ ions. Notably, the incorporation of Tb 3+ ions enhanced exciton-phonon coupling and lattice vibrations , resulting in strengthened STEs emission. Furthermore, tunable emission from green to yellow was achieved through multiple ET processes in Cs 2 KInCl 6 :Tb 3+ ,Sm 3+ by co-doping Tb 3+ and Sm 3+ . This work not only offers new insights into enhancing STEs emission in DPs, but also imparts Cs 2 KInCl 6 with tunable PL properties, which makes it a promising candidate for multicolor light-emitting devices.