High Efficiency NIR Luminescence Beyond 900 nm Through Promoting Cr3+ Pair Generation in Sr3Zr2O7 Layered Perovskite

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).