Facile Microwave Synthesis of a Narrow-Band Green-Emitting Phosphor Cs₃MnBr₅ and the Effect of Anion Substitution on Its Luminescence Properties

A bright blue light excitable and narrow-band green-emitting phosphor Cs₃MnBr₅ has been synthesized by a facile microwave radiation method within 2 min. The influence of the matrix on its steady-state and transient-state luminescence properties is investigated by partial substitution of Br^– ions by Cl^– ions. The incorporation of Cl^– ions in Cs₃Mn­(Br_1–xCl_x)₅ resulted in almost no change in the emission maxima of Mn²⁺, which is attributed to the synergistic effect of reduced covalency and increased crystal field strength caused by the replacement of Br^– ions by Cl^– ions. Meanwhile, the emission of Mn²⁺ decreases with the increasing Cl^– content, which is caused by different thermal quenching of Mn²⁺ emission in the mixed Cl^–/Br^– coordination. Moreover, the incorporation of Cl^– in Cs₃Mn­(Br_1–xCl_x)₅ was found to have different effects on the lifetime of Mn²⁺ at different temperatures, that is, at room temperature, the lifetime of Mn²⁺ decreases with the increasing Cl^– content, while at liquid nitrogen temperature, the lifetime of Mn²⁺ increases upon increasing the Cl^– content. The former is due to the different thermal quenching for different coordinations of Mn²⁺ with Cl^– and Br^–, while the latter is due to the weaker spin–orbit coupling of the Mn²⁺ ion caused by the interaction with the lighter Cl^– ions, which makes the spin selection rule stricter and leads to a longer lifetime of Mn²⁺ consequently.