Broad-Band Sensitization in Cr<sup>3+</sup>–Er<sup>3+</sup> Co-Doped Cs<sub>2</sub>AgInCl<sub>6</sub> Double Perovskites with 1.5 μm Near-Infrared Emission
Weijiang Gan, Luyu Cao, Simin Gu, Huiwang Lian, Zhiguo Xia, Jing Wang
Abstract
Lanthanide (Ln 3+ )-doped metal halide perovskites with near-infrared (NIR) luminescence have received great attention; however, they suffer from low NIR efficiency, especially for 1.5 μm emission of Er 3+ ions. Herein, a Cr 3+ –Er 3+ co-doped Cs 2 AgInCl 6 double perovskite is successfully synthesized using a simple solution precipitation method. Besides a broad-band NIR emission of 4 T 2 → 4 A 2 transition of Cr 3+ ions centered at 1010 nm, the co-doped sample exhibits an NIR-II emission peak at 1540 nm assigned to the 4 I 13/2 → 4 I 15/2 transition of Er 3+ ions. Er 3+ ions can be sensitized by Cr 3+ ions that have broad-band absorption from ultraviolet to NIR region (250–900 nm). Excitingly, through assisted simple post-annealing treatment to eliminate defect states, the Cr 3+ –Er 3+ co-doped sample obtains an unprecedented high NIR photoluminescence quantum yield (PLQY) of 57.5% (Er 3+ emission: ∼29.0%), which is the highest value for the Ln 3+ -doped lead-free perovskites at present. The admirable stability and dual NIR bands of Cr 3+ –Er 3+ co-doped Cs 2 AgInCl 6 pave the way for NIR light sources pumped by multicolor light-emitting diode (LED) chips in potential optical communication, night-vision, and infrared imaging applications.