Narrow-band violet and blue emission of Bi3+ in M10P6O25 (M = Ca, Sr) based on highly symmetric crystal structure

Abstract

Phosphor materials with narrow emission bands are highly interesting for light-emitting diode (LED) lighting and display applications. However, designing novel Bi3+-doped phosphors with desirable narrow band emission, high luminous efficiency and good thermal stability is a challenging task. Here, two novel violet- and blue-emitting narrow-band M10P6O25:Bi3+ (M = Ca, Sr) phosphors are designed based on the small Stokes shift and introduction of Bi3+ into highly symmetric lattice sites. Both phosphors exhibit a broad absorption band in 300–380 nm, matching well with the n-UV LED chip. Under UV light excitation, Ca10P6O25:Bi3+ shows a violet emission peaking at 392 nm with a narrow full width at half-maximum (FWHM) of 36 nm and high color purity of 98%. Sr10P6O25:Bi3+ emits a blue light (400–550 nm) with FWHM of 66 nm and color purity of 88%. More importantly, the as-prepared M10P6O25:Bi3+ (M = Ca, Sr) phosphors show good thermal stability (>82%@150 °C) and relatively high photoluminescence quantum yields (PLQY >50%). Moreover, violet LED fabricated with Ca10P6O25:Bi3+ can be used in anti-counterfeiting. The as-fabricated white LED utilizing Sr10P6O25:Bi3+ possesses a CIE chromaticity coordinates of (0.345, 0.363), color rendering index (CRI) of 87.5 and correlated color temperature (CCT) of 4992 K. The above investigations indicate that M10P6O25:Bi3+ (M = Ca, Sr) are promising violet and blue phosphor candidates for LED with wide-color-gamut display and potential anti-counterfeiting applications.

Keywords

• Bi3+
• Narrow band emission
• High symmetry
• Phosphor materials
• LED