High Efficiency NIR Luminescence Beyond 900 nm Through Promoting Cr ³⁺ Pair Generation in Sr ₃ Zr ₂ O ₇ Layered Perovskite

ABSTRACT The near‐infrared (NIR) light of 900–1100 nm exhibits enormous application potential in fields such as optical communication and biological detection. However, high‐efficiency phosphors emitting beyond 900 nm remain extremely limited due to non‐radiative deactivation. In this study, a 455 nm blue light excitable NIR phosphor that efficiently emits in the wide range of 700–1200 nm (peaking at ∼960 nm) was obtained through Cr 3+ /La 3+ codoping of Ruddlesden‐Popper type Sr 3 Zr 2 O 7 perovskite, whose internal/external quantum efficiencies (%) and thermal stability of luminescence ( I 423 / I 298 , %) reached ∼92.4/57.5 and 73, respectively. Experimental and theoretical analysis found the decisive role of the La 3+ codopant in Cr 3+ luminescence: it not only inhibited Cr 3+ from oxidation but also attracted the Cr 3+ ions to aggregate around it to form Cr 3+ –Cr 3+ pairs for the aforesaid excellent luminescence. Combining the NIR phosphor with a Si‐PIN photodetector created a highly effective blue‐to‐NIR conversion unit, demonstrating the application potential of the phosphor for underwater wireless optical communication (UWOC).