Chemical Group Substitution Enables Highly Efficient Mn4+ Luminescence in Heterovalent Systems

 https://doi.org/10.1002/adom.202300076

Defects are a double-edged sword for heterovalent metal-ion doping phosphors. Along with the luminescence tunability of phosphors bestowed by defects, their expected luminescence efficiency would also be inevitably lowered due to the presence of these quenching sites. Herein, a chemical group substitution strategy is proposed, where inorganic polyhedrons act as the smallest chemical units during the structural evolution of the doping process. Such a method can not only effectively prevent the defect generation for charge compensation in heterovalent doping systems, but also facilitate the incorporation of activators into the matrix, leading to extremely high luminescence efficiency. The concept is first confirmed energetically favorable by first-principles simulations. As a robust experimental proof, two newly reported Mn⁴⁺-incorporated hexavalent organic-inorganic hybrid oxyfluorides (TMA)₂BO₂F₄:Mn⁴⁺ (where TMA stands for tetramethylammonium, and B = W⁶⁺ or Mo⁶⁺) present high quantum efficiency (up to 94.4%) and short lifetime (down to 2.26 ms) that are superior to the commercial red phosphor K₂SiF₆:Mn⁴⁺ (≈84.8%, ≈8.06 ms). Utilizing the differences in decay lifetimes and thermal quenching behaviors of (TMA)₂BO₂F₄:Mn⁴⁺ and K₂SiF₆:Mn⁴⁺, a time- and temperature-resolved single-color multiplexing mode with high-safety and easy-access is developed for information security. This work offers an effective strategy to manipulate defect generation in luminescent materials.