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

Abstract 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 (Ln 3+ ) ions doped Cs 2 M(In 0.95 Sb 0.05 )Cl 6 (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 Cs 2 M(In 1− x Sb x )Cl 6 NCs can break the forbidden of f‐f transition of Ln 3+ , thus increasing their radiative transition rates and simultaneously boosting the energy transfer efficiency from host to Ln 3+ . Finally, the wide‐coverage NIR LEDs based on Sm 3+ , Nd 3+ , Er 3+ ‐tridoped Cs 2 K 0.5 Rb 0.5 (In 0.95 Sb 0.05 )Cl 6 NCs are fabricated and employed in the multiplex gas sensing and night‐vision application.