A novel white light-emitting diode (w-LED) fabricated with Sr6BP5O20:Eu2+ phosphor

Sr6BP5O20:Eu2+ phosphor was prepared by the solid-state reaction method under a weak reductive atmosphere and the photoluminescence properties were studied systematically. The bluish-green emission band of Sr6BP5O20:Eu2+ phosphor is peaking at 475 nm, and the excitation bands are broad with peaks at about 290 and 365 nm with a shoulder around 390 nm, respectively. By combining with Ga(In)N-based near-ultraviolet LEDs, a bluish-green LED was fabricated based on the Sr6BP5O20:Eu2+ phosphor, and a novel intense white LED was fabricated based on the bluish-green phosphor Sr6BP5O20:Eu2+ and the red phosphor (Sr,Ca)5(PO4)3Cl:Eu2+,Mn2+. When this two-phosphor white LED is operated under 20-mA forward-bias current at room temperature, the Commission Internationale de l’Eclairage(CIE) chromaticity coordinates (x,y), the correlated color temperature Tc, and the color rendering index Ra are calculated to be (0.3281,0.3071), 5687 K, and 87.3, respectively. The dependence of the bluish-green and two-phosphor white LEDs on different forward-bias currents from 5 mA to 50 mA shows a similar behavior. As the current increases, the relative intensity simultaneously increases. The CIE chromaticity coordinates (x,y) of the two-phosphor white LED tend to decrease. Consequently, the correlated color temperature Tc increases from 3800 K to 9400 K and the color rendering index Ra of the two-phosphor white LED increases from 83.4 to 91.8 simultaneously.