Site occupancy and photoluminescence properties of cyan-emitting K2Ca2Si2O7:Bi3+ phosphor for white light emitting diodes

Abstract Exploring novel cyan-emitting phosphor can compensate the “cyan gap” in the spectra of traditional phosphor converted white light emitting diodes (pc-WLEDs) for achieving high-quality full-spectrum white lighting. Herein, a broadband cyan-emitting K2Ca2Si2O7:Bi3+ phosphor with emission peak at 490 nm is developed to fill aforesaid “cyan gap”. The structure and optical properties are characterized by X-ray diffraction combined with Rietveld refinement of the structure, X-ray spectroscopy, high-resolution transmission electron microscopy, diffuse reflectance spectrum and photoluminescence spectra. The asymmetric broad emission is originated from the accommodation of Bi3+ ions in the two types of Ca2+ sites and K (6) site, respectively. The concentration quenching mechanism in K2Ca2Si2O7:xBi3+ phosphors is proved to be dipole-dipole interaction. With increasing Bi3+ doping content (x), Bi3+ dopants may migrate from the two types of Ca2+ sites to K (6) site, resulting in an obvious blue shift of K2Ca2Si2O7:xBi3+ emission spectra. These results indicate that the as-synthesized K2Ca2Si2O7:Bi3+ phosphor may find potential applications in n-UV excited full-spectrum white LEDs.