Insight into the optical evaluation of sunlike LED devices with full-visible spectrum emission based on ultra-low melting tin fluorophosphate glass for human centric lighting

Abstract

Full spectrum sunlike light-emitting diode (LED) devices in the wavelength range of 380–670 nm have received much attention for their applications in human centric lighting. Herein, the inorganic color converter of the sunlike phosphor-in-glass (PiG) has been developed by embedding the green-emitting (Lu3-xYxAl5O12: Ce3+) and red-emitting (Sr0.6Ca0.4AlSiN3: Eu2+) phosphor powders in ultra-low melting tin fluorophosphate glass. Notably, the sunlike PiG exhibits the full spectrum in the wavelength range of 380–670 nm under the excitation of a near-ultraviolet (NUV) chip. Tunable color temperature (2785 K–5806 K) and high color rendering index (Ra = 95) were obtained by varying the mix ratio of the red-emitting component in the glass matrix. Further, the full visible spectrum emission was regulated by adjusting the Lu/Y ratio of the green phosphor Lu3-xYxAl5O12: Ce3+ and the color quality was further optimized (Ra = 97). The color quality of white light-emitting diode (WLED) was systematically investigated using Illuminating Engineering Society (IES) of North America evaluation systems and the LED devices exhibit fidelity index (Rf) and gamut index (Rg) close to sunlight (Rf = 95, Rg = 101). Compared with the traditional phosphor-in-silicone (PiS), the sunlike PiG based WLED exhibits a low working temperature of ∼37 °C for high power LED. Therefore, the WLED devices based on sunlike-PiG can be regarded as promising candidates for ultra-high color rendering index light sources because of the adjustable color temperature, high color quality, low-efficiency loss, excellent thermal properties and water stability.