Eliminating disorderly A sites: Significantly enhanced external quantum efficiency of Bi ³⁺ luminescence in double perovskite phosphor

Abstract Highly efficient inorganic phosphors activated with Bi 3+ are increasingly needed due to their fascinating multicolor luminescence and versatile applications. Nevertheless, achieving high external quantum efficiency (EQE) is challenging. Here, ordering A sites in double perovskite structure develops a highly efficient Bi 3+ ‐activated A 2 BB'O 6 phosphor, in which the EQE is boosted by 3.9 times. The transformation from the disordered A sites in Ca 2 LaNbO 6 (CLNO) to the ordered A sites in Ca 2 YNbO 6 (CYNO) occurs via the full substitution of Y 3+ for La 3+ . Bi 3+ activators occupy the A and B sites, which is confirmed by direct aberration‐corrected transmission electron microscopy (AC‐TEM) proof, as well as the theoretical and spectral proofs. Subsequently, a representative CYNO:1%Bi 3+ product is practically applied, exhibiting superior fluorescence thermometer ( S r‐max = 3.12% K −1 at 473 K), high color rendering index lighting ( R a = 91), and accurate latent fingerprint detecting performances. This work invigorates the progress of Bi 3+ ‐activated phosphors with high EQE for versatile utilizations. image