Defect-induced deep red luminescence of CaGdAlO₄-type layered perovskites: multi-cationic sites partial/full...

A series of CaGdAlO₄-type layered perovskite phosphors showing deep red luminescence (λ_em = 711 nm, λ_ex = 338 nm) were synthesized via a solid-state reaction. A comprehensive analysis performed via photoluminescence, X-ray photoelectron spectroscopy, thermoluminescence, and fluorescence decay revealed that the deep red luminescence is related to oxygen defects and particularly oxygen interstitials. The defect-related luminescence was effectively regulated through partial substitution of multi-cationic sites (the Ca²⁺ site with Mg²⁺, Sr²⁺, and Ba²⁺; the Gd³⁺ site with La³⁺, Y³⁺, and Lu³⁺) and full substitution of Gd³⁺ with Y³⁺. Remarkably, a 383.3% stronger luminescence was obtained through partial substitution with Lu³⁺, and the quantum yield of luminescence reached 28.74%, which is higher than those values of most previously reported self-luminescent systems. A pc-LED device was fabricated using this phosphor, and the device was shown to have potential application in indoor plant cultivation.