Intense green light emission in Sr₂ ZnGe₂ O₇ :Mn²⁺ phosphors by the design of high symmetry melilite structure

A green phosphor Sr₂ ZnGe₂ O₇ :Mn²⁺ with a melilite structure was prepared using a high-temperature solid-state reaction. When the 535 nm emission was monitored, the excitation spectrum of the Sr₂ ZnGe₂ O₇ :Mn²⁺ was found to contain two excitation bands in the ultraviolet (UV) region. When excited by UV light, the sample shows bright green emission at 535 nm, which corresponds to the distinctive transition of Mn²⁺ (⁴ T₁ →⁶ A₁ ). Moreover, the quantum efficiency of Sr₂ ZnGe₂ O₇ :Mn²⁺ could reach 67.6%. Finally, a high-performance white-light-emitting diode (WLED) with a low correlated colour temperature of 4632 K and a high colour rendering index (CRI) of 92.3 were packaged by coating commercial blue and red phosphors with an optimized Sr₂ ZnGe₂ O₇ :Mn²⁺ sample on a 310 nm UV chip. This indicated that Sr₂ ZnGe₂ O₇ :Mn²⁺ has the potential application as a green component in the WLED lighting field.