A novel narrow-band blue-emitting phosphor of Bi3+-activated Sr3Lu2Ge3O12 based on a highly symmetrical crystal structure used for WLEDs and FEDs

Investigating highly efficient narrow-band emission phosphors that have strong excitation bands in the near-ultraviolet (NUV) region is the main goal of the present light-emitting diode (LED) research, especially for Bi3+-activated phosphors. The naked 6s and 6p electrons of Bi3+ are sensitive to the microenvironment, thus leading to broad emission bands, while most Bi3+-activated phosphors suffer from low absorption of NUV-LED chips. Here, we report on a narrow-band blue-emitting garnet-type phosphor of Sr3Lu2Ge3O12: Bi3+ that is available for NUV-LED chips; its full width of the half maximum (FWHM) is limited to 40 nm, which is comparative to rare earth-activated phosphors, such as commercial blue phosphor BaMgAl10O17: Eu2+ (FWHM ≈ 52 nm), and this phenomenon is extremely rare among most Bi3+-activated phosphors. The internal quantum efficiency (IQE) of Sr3Lu2Ge3O12: Bi3+ can reach 57%. Moreover, it is interesting to find that Sr3Lu2Ge3O12: Bi3+ also exhibits exalting cathodoluminescence properties and its narrow-band emission produces brilliant images with high color saturation. The significant luminescent properties of trivalent bismuth are ascribed to the compact and highly symmetrical crystal structure of Sr3Lu2Ge3O12; thus, the discussion of the structure-property relations for Bi3+-activated Sr3Lu2Ge3O12 is the most anticipated part of this work. The results pave the way for the design of better Bi3+-activated phosphors for use as white light emitting diodes (WLEDs) and field emission displays (FEDs).