Transition-metal activated phosphors are an important family of luminescent materials that can produce white light with an outstanding color rendering index and correlated color temperature for use in light-emitting diodes. In recent years, work in this quite “hot” research field has focused on the development of Mn²⁺ and Mn⁴⁺ activated red phosphors. In this review article, we provide an overview of recent studies on Mn²⁺ and Mn⁴⁺ doped phosphors, including detailed synthesis routes (solid-state reaction and wet-chemical synthesis) and description of luminescence mechanisms and phosphors’ behaviors; discuss their promising applications in white light-emitting diodes; and present an extensive list of references to representative works in this field.

In this paper we review the spectroscopic properties of the Mn⁴⁺ ion (3d³ electronic configuration) and establish a relationship between the energy of the ²E_g → ⁴A_2g emission transition and the covalence of the “Mn⁴⁺-ligand” bonding. A new parameter (where (B, C (B₀, C₀) are the Racah parameters of the Mn⁴⁺ ions in a crystal (free state), respectively) was recently introduced that allows for establishing a linear relationship between β₁ and the energy of the ²E_g level. This makes it possible to understand the large variation in the energy of the ²E_g → ⁴A_2g emission transition that is frequently encountered in the spectroscopy of the Mn⁴⁺ ions in solids.