Wide-coverage and Efficient NIR Emission from Single-component Nanophosphors through Shaping Multiple Metal-halide Packages.

Wide-coverage near infrared (NIR) phosphor-converted LEDs possess promising potential for practical applications, but little is developed towards the efficient and wide-coverage NIR phosphors. Here, we report the single-component lanthanide (Ln3+ ) ions doped Cs2 M(In0.95 Sb0.05 )Cl6 (M=alkali metal) nanocrystals (NCs), exhibiting emission from 850 to 1650 nm with high photoluminescence quantum yield of 20.3 %, which is accomplished by shaping the multiple metal halide octahedra of double perovskite via the simple alkali metal substitution. From Judd-Ofelt theoretical calculation and spectroscopic investigations, the shaping of metal halide octahedra in Cs2 M(In1-x Sbx )Cl6 NCs can break the forbidden of f-f transition of Ln3+ , thus increasing their radiative transition rates and simultaneously boosting the energy transfer efficiency from host to Ln3+ . Finally, the wide-coverage NIR LEDs based on Sm3+ , Nd3+ , Er3+ -tridoped Cs2 K0.5 Rb0.5 (In0.95 Sb0.05 )Cl6 NCs are fabricated and employed in the multiplex gas sensing and night-vision application.