Highly Efficient Broad-Band Green-Emitting Cerium(III)-Activated Garnet Phosphor Allows the Fabrication of Blue-Chip-Based Warm-White LED Device with a Superior Color Rendering Index.

High-performance warm-white light-emitting diode (LED) devices are in great demand toward green and comfortable solid-state lighting. Herein, we report a creative green-emission CaYHfGa(AlO):Ce phosphor. CaYHfGa(AlO):Ce compounds with different cerium ion doping contents have been successfully prepared through a conventional high-temperature solid-state method, and their phase and crystal structure have been revealed via the powder X-ray diffraction and Rietveld refinement. Impressively, the CaYHfGa(AlO):Ce phosphors exhibit a broad-band excitation, which well covers the wavelength region from the 300 to 500 nm, corresponding to the commercial blue-emitting LED chip. Upon 450 nm excitation, the optimal CaYHfGa(AlO):2%Ce sample shows an intense broad-band green emission (the corresponding testing spectral range: 460-750 nm) with a strongest peak about 534 nm. In addition, the CaYHfGa(AlO):2%Ce sample possesses a broad full width at half-maximum equal to 120 nm; moreover, its CIE chromaticity coordinate and the internal quantum efficiency are determined to be (0.3541, 0.5427) and 72.8%, respectively. A high-quality warm-white LED has been fabricated through incorporating our CaYHfGa(AlO):2%Ce green phosphors and commercial red phosphors with the 450 nm blue LED chip. When upon the 20 mA bias driving current, the LED device demonstrates a bright warm-white light emission, which possesses a satisfactory color rendering index of 91, a low correlated color temperature of 4080 K, as well as a good luminous efficacy of 85.14 lm W. The creative green-emitting CaYHfGa(AlO):Ce garnet phosphor has a bright application prospect toward high-quality warm-white LED lighting.