Broad-Band Sensitization in Cr3+–Er3+ Co-Doped Cs2AgInCl6 Double Perovskites with 1.5 μm Near-Infrared Emission

Lanthanide (Ln3+)-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 Er3+ ions. Herein, a Cr3+–Er3+ co-doped Cs2AgInCl6 double perovskite is successfully synthesized using a simple solution precipitation method. Besides a broad-band NIR emission of 4T2 → 4A2 transition of Cr3+ ions centered at 1010 nm, the co-doped sample exhibits an NIR-II emission peak at 1540 nm assigned to the 4I13/2 → 4I15/2 transition of Er3+ ions. Er3+ ions can be sensitized by Cr3+ 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 Cr3+–Er3+ co-doped sample obtains an unprecedented high NIR photoluminescence quantum yield (PLQY) of 57.5% (Er3+ emission: ∼29.0%), which is the highest value for the Ln3+-doped lead-free perovskites at present. The admirable stability and dual NIR bands of Cr3+–Er3+ co-doped Cs2AgInCl6 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.