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 K 2 Ca 2 Si 2 O 7 :Bi 3+ 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 Bi 3+ ions in the two types of Ca 2+ sites and K (6) site, respectively. The concentration quenching mechanism in K 2 Ca 2 Si 2 O 7 :xBi 3+ phosphors is proved to be dipole-dipole interaction. With increasing Bi 3+ doping content (x), Bi 3+ dopants may migrate from the two types of Ca 2+ sites to K (6) site, resulting in an obvious blue shift of K 2 Ca 2 Si 2 O 7 :xBi 3+ emission spectra. These results indicate that the as-synthesized K 2 Ca 2 Si 2 O 7 :Bi 3+ phosphor may find potential applications in n -UV excited full-spectrum white LEDs. • A novel cyan-emitting K 2 Ca 2 Si 2 O 7 :Bi 3+ phosphor are successfully prepared. • The distribution of Bi 3+ in different cation sites results in a broad emission. • The color tune can be adjusted by increasing the Bi 3+ doping content.