Color-Tunable Pr3+-Activated Dual-Emission Tantalate Materials for Warm Lighting LEDs

Currently, the lack of efficient red/orange-light phosphor interferes with the performance improvement of white light emitting diodes (WLEDs) because of notably low color rendering index. Multicolor phosphors are considered to be able to solve the aforesaid shortcoming of existing WLEDs when assembled with ultraviolet or blue LED chips, thus the development of dual-emission phosphors has been a popular research field. Here, we synthesized a series of Li 2 SrTa 2 O 7 :Pr 3+ /Gd 3+ phosphor materials, and investigated their crystal structure and luminescent properties, including X-ray diffraction, diffuse reflectance spectra, photoluminescence, long-persistent luminescence. Results reveal that Li 2 SrTa 2 O 7 :Pr 3+ /Gd 3+ phosphors exhibit two dominant photoluminescence emission peaks at 495 nm and 620 nm respectively upon 295 nm excitation, showing bright yellow-green to the naked eyes, while their afterglow spectra show orange emission peaking at 620 nm. Their light color of photoluminescence emission can change from yellow-green to red with increasing temperature (300-490 K) along with minor thermal quenching. Moreover, an excellent orange LED lamp with the CIE chromaticity coordinates of (0.3986, 0.3832), the CCT of 3591 K is obtained by fabricating Li 1.99 SrTa 2 O 7 :4%Pr 3+ /4%Gd 3+ phosphor with a 310 nm LED chip. This research provides a practical foundation to understand and regulate the luminescent performance, and proposes a new strategy to realize warm light illumination of pc-LED devices.