A Full‐Site Regulation Strategy Facilitates Efficient Near‐Infrared Emission: Towards Non‐Line‐of‐Sight Optical Communication and Dynamic Encryption Applications

ABSTRACT Currently, Cr 3+ ‐activated near‐infrared (NIR) phosphors are hindered by a severe trade‐off between emission redshift and efficiency loss. Their insufficient stability in complex environments further restricts practical applications. To overcome this bottleneck, a full‐site regulation strategy was implemented based on a novel CaY 2 Ga 4 SiO 12 : Cr 3+ garnet model. A “two‐ion, three‐site” synergistic regulation mechanism was proposed and verified for the first time. Through the synergistic co‐substitution of Li + and Ge 4+ , trans‐coordination migration and occupancy of ions were induced across three key sites: dodecahedral, octahedral, and tetrahedral. This atomic‐scale site reconstruction was directly observed via aberration‐corrected transmission electron microscopy (AC‐TEM). Combined with Density functional theory (DFT) calculations, it was confirmed that this multi‐site coordination mechanism reshapes the crystal field environment and enhances structural rigidity through a charge self‐compensation effect. This engineering drives the emission peak redshift to 810 nm while pushing the internal quantum efficiency (IQE) to 93%. Due to its superior optoelectronic properties, this material enables robust non‐line‐of‐sight (NLOS) optical communication through obstacles. Additionally, a multi‐level spatiotemporal dynamic encryption platform was constructed by leveraging unique differences in chemical kinetics. This work provides a new design paradigm for high‐performance and multifunctional NIR optoelectronic applications.