Halide Double Perovskite Nanocrystals Doped with Rare‐Earth Ions for Multifunctional Applications

Most lead‐free halide double perovskite materials display low photoluminescence quantum yield (PLQY) due to the indirect bandgap or forbidden transition. Doping is an effective strategy to tailor the optical properties of materials. Herein, efficient blue‐emitting Sb(3+)‐doped Cs(2)NaInCl(6) nanocrystals (NCs) are selected as host, rare‐earth (RE) ions (Sm(3+), Eu(3+), Tb(3+), and Dy(3+)) are incorporated into the host, and excellent PLQY of 80.1% is obtained. Femtosecond transient absorption measurement found that RE ions not only served as the activator ions but also filled the deep vacancy defects. Anti‐counterfeiting, optical thermometry, and white‐light‐emitting diodes (WLEDs) are exhibited using these RE ions‐doped halide double perovskite NCs. For the optical thermometry based on Sm(3+)‐doped Cs(2)NaInCl(6):Sb(3+) NCs, the maximum relative sensitivity is 0.753% K(−1), which is higher than those of most temperature‐sensing materials. Moreover, the WLED fabricated by Sm(3+)‐doped Cs(2)NaInCl(6):Sb(3+) NCs@PMMA displays CIE color coordinates of (0.30, 0.28), a luminous efficiency of 37.5 lm W(−1), a CCT of 8035 K, and a CRI over 80, which indicate that Sm(3+)‐doped Cs(2)NaInCl(6):Sb(3+) NCs are promising single‐component white‐light‐emitting phosphors for next‐generation lighting and display technologies.