Modulation of Bi 3+ luminescence from broadband green to broadband deep red in Lu 2 WO 6 by Gd 3+ doping and its applications in high color rendering index white LED and near-infrared LED.

Phosphors that exhibit tunable broadband emissions are highly desired in multi-functional LEDs, including pc-WLEDs and pc-NIR LEDs. In this work, broadband emissions were obtained and modulated in the unexpectedly wide spectral range of 517-609 nm for (Lu 0.99- x Gd x Bi 0.01 ) 2 WO 6 phosphors by tuning the Gd 3+ content ( x = 0-0.99). The effects of Gd 3+ doping on phase constituents, particle morphology, crystal structure, and photoluminescence were systematically investigated. Broadband green emission was obtained from Gd 3+ -free (Lu 0.99 Bi 0.01 ) 2 WO 6 phosphors ( x = 0), whose emission intensity was enhanced by 50% with 5 at% Gd 3+ ( x = 0.05). The phase transition happened when x > 0.50 and the broadband red-NIR emission was obtained when x = 0.75-0.99. Three luminescence centers were proved to be responsible for the broadband green emissions via crystal structure, spectral fitting and fluorescence decay analysis. A pc-WLED with a high color rendering index ( R a = 91.3), a stable emission color, and a low color temperature (3951 K) was fabricated from the (Lu 0.94 Gd 0.05 Bi 0.01 ) 2 WO 6 broadband green phosphor, and an LED device that simultaneously emits high color rendering index white light and NIR light was obtained with the (Gd 0.99 Bi 0.01 ) 2 WO 6 broadband red-NIR phosphor. Night vision and noninvasive imaging were also demonstrated using the latter LED device.