Modulation of Bi3+ luminescence from broadband green to broadband deep red in Lu2WO6 by Gd3+ 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 (Lu0.99-xGdxBi0.01)2WO6 phosphors via tuning the Gd3+ content (x = 0-0.99). The effects of Gd3+ doping on phase constituent, particle morphology, crystal structure, and photoluminescence were systematically investigated. Broadband green emission was obtained with the Gd3+-free (Lu0.99Bi0.01)2WO6 phosphor (x = 0), whose emission intensity was enhanced by 50%
with 5 at% of Gd3+ (x = 0.05). Phase transition happened when x ＞ 0.50, and broadband red-NIR emission was obtained when x = 0.75-0.99. Three luminescence centers were proved to be responsible for the broadband emissions via crystal structure, spectral fitting and fluorescence decay analysis. A pc-WLED with high color rendering index (Ra = 91.3), stable emission color, and low color temperature (3951 K) was fabricated from the (Lu0.94Gd0.05Bi0.01)2WO6 broadband green phosphor, and an LED device that simultaneously emits high color rendering white light and NIR light was obtained with the (Gd0.99Bi0.01)2WO6 broadband red-NIR phosphor. Night version and noninvasive imaging were also demonstrated for the latter LED device.