High R14 warm white light phosphor in glass for high power LED prepared by epoxy resin system

Warm white light-emitting diodes (WLEDs) with a high special color rendering index (R14) are indispensable in plant growth applications. They not only provide the orange light component required for chlorophyll to carry out photosynthesis, but also enhance the detection of leaf abnormalities by accurately restoring the green color of the leaves. To address the limitations of traditional phosphor materials in high-power LED devices, a high R14 temperature white glass phosphor (PiG) was fabricated. Uniform and dense PiG samples were prepared by optimizing the ratio of glass to phosphor (GtP) and using an environmentally friendly epoxy resin system. XRD and SEM characterization confirmed the uniform distribution of YAGG:Ce and GdYAG:Ce phosphors in the glass matrix. Rheological analysis confirmed that gel casting could obtain slurries with high solid load and low viscosity. This guaranteed the preparation of uniform and dense PiGs. It also had excellent thermal stability and optical performance. Under the excitation of the LED with a specification of 50W, the maximum operating temperature of the PiG within 30 min was 138.7 °C. From the tenth minute on, the surface temperature of PiG reached a dynamic equilibrium and was basically maintained at around 135 °C. PiG with adjustable color temperature (3184- 4005k) could be produced by using green phosphor YAGG:Ce and orange phosphor GdYAG:Ce. Low color temperature and high R14 value were of great significance for plant photosynthesis and rapid diagnosis of plants. The comparative experiment confirmed this view. The average SPAD value of lettuce under the irradiation of warm white LED was 29.1, which was higher than that of 25.7 under natural light.