Ruddlesden-Popper type Sr(La,Gd)2Al2O7:Cr3+ layered perovskite new phosphors for NIR pc-LED application

Near-infrared phosphor converted light-emitting diodes (NIR pc-LEDs), as a state-of-the-art type of NIR sources, are finding multifaceted applications, where phosphor is a crucial component. In hope to provide new choices for NIR lighting, we synthesized in this work the two series of Ruddlesden -Popper type layered perovskite phosphors of SrLa 2 Al 2- x O 7 : x Cr 3+ ( x  = 0–0.02) and SrLa 2- y Gd y Al 1.984 O 7 :0.016Cr 3+ ( y  = 0–2), followed by detailed structure and luminescence investigation. SrLa 2 Al 2- x O 7 : x Cr 3+ was found to emit ∼700–800 nm NIR light under UV excitation and be able to maintain ∼54.3 % of its room temperature intensity at 423 K, which is remarkably higher than those (∼25–30 %@423 K) of the Mn 4+ activated perovskite NIR phosphors. Luminescence regulation was achieved by substituting La 3+ with Gd 3+ , and it was revealed that Gd 3+ may act as a sensitizer to significantly enhance Cr 3+ luminescence (∼346 % at 77 K) through Gd 3+ → Cr 3+ energy transfer, which was confirmed by spectral and fluorescence lifetime analysis. The observed spectral features and the influence of Gd 3+ were rationalized by considering crystal structure, local coordination, and crystal field. Finally, an NIR pc-LED device showing strong ∼700–900 nm luminescence was fabricated to show potential application of the phosphor in night vision and plant lighting.