Mechanochemical Fabrication of a Mn⁴⁺-Activated Inorganic Rb₂KTiOF₅ Perovskite Red Phosphor for White Light-Emitting Diodes

Abstract

Mn4+-activated oxyfluoride hosts are of great interest, due to the strong distortion of metal–(O/F) polyhedra in the crystal lattice. Extensive studies have been conducted to synthesize the chemical compositions of these easily deformable structures to manipulate and achieve their good physical properties. Here, we report a series of Rb2KTiOF5 red phosphors that, when doped with Mn4+, produce efficient red emission. The low formation energy of Mn-doped Rb2KTiOF5 and Ti-doped K2MnF6 validated the phenomenon of stress-induced ion exchange, on the basis of density functional theory calculations. We obtained an optimal quantum efficiency of 56.8% and enhanced the color purity of Rb2KTiOF5:Mn4+ (∼96.4), which could persist at ∼420 K without degradation and maintain 80% of the initial luminescence intensity at 300 K. A white light-emitting diode with a wide color gamut (123%) of the National Television System Committee standard was fabricated with the Rb2KTiOF5:Mn4+ red phosphor, green-emitting CsPbBr3 quantum dots, and a commercial blue chip (450 nm). This work not only affords a novel Mn4+-activated oxyfluoride red phosphor but also provides a safe way to further explore Mn4+-doped fluoride or oxyfluoride.