A novel Mn4+-activated Li3CsGe8O18 red phosphor and cation substitution induced photoluminescence improvement

Nowadays, non-rare-earth Mn 4+ -activated red phosphors have emerged for improvement of the lighting quality of phosphor-converted white light-emitting-diodes (pc-WLED), owing to the low cost and the admirable luminescence properties. In this work, a novel narrow-band red-emitting Li 3 CsGe 8 O 18 :Mn 4+ phosphor was synthetized based on the component substitution from Li 3 RbGe 8 O 18 , which exhibits the red luminescence centered at 668 nm upon 466 nm excitation. By further designing [Cs + -Rb + ] cation substitution, the photoluminescence intensity and luminescence efficiency are obviously improved. The photoluminescence intensity enhanced 1.75 times than Li 3 RbGe 8 O 18 :Mn 4+ phosphor, while the corresponding internal quantum efficiency (IQE) increased by 1.57 times. According to the Rietveld refinement results, the corresponding mechanism of luminescence enhancement is attributed to the smaller distortion degree of the [Ge(1)O 6 ] octahedron . The pc-WLED device is fabricated by the optimal Li 3 Cs 0.5 Rb 0.5 Ge 8 O 18 :1%Mn 4+ red phosphor, yellow phosphor with Y 3 Al 5 O 12 :Ce 3+ and 460 nm InGaN chip, showing a warm white light emission with low correlated color temperature (4474K) and high color rendering index (90.8). The result implies that the Li 3 Cs 0.5 Rb 0.5 Ge 8 O 18 :1%Mn 4+ phosphor can be used as a potential red phosphor for pc-WLED application.