Light extraction enhanced white light-emitting diodes with multi-layered phosphor configuration.

Area of Science:

• Solid State Lighting
• Materials Science
• Optoelectronics

Background:

• Phosphor-converted white light-emitting diodes (LEDs) are crucial for modern illumination.
• Conventional LEDs often use randomly mixed phosphors, which can limit performance.
• Optimizing phosphor arrangement is key to enhancing LED efficiency and thermal management.

Purpose of the Study:

• To investigate a novel bi-layered phosphor packaging scheme for white LEDs.
• To compare the performance of bi-layered phosphors against conventional mixed phosphors.
• To evaluate the impact on luminous flux, junction temperature, and phosphor conversion efficiency.

Main Methods:

• Fabrication of white LEDs using separate red and yellow phosphor layers in a bi-layered configuration.
• Testing under current regulation conditions to assess performance metrics.
• Comparison with white LEDs utilizing randomly mixed phosphor layers.

Main Results:

• A bi-layered phosphor scheme achieved over 18% increase in luminous flux at the same correlated color temperature.
• Lower junction temperatures were observed in bi-layered phosphor white LEDs due to reduced back reflection.
• Enhanced phosphor conversion efficiency and light extraction were attributed to the bi-layered structure.
• Chromaticity coordinate shifts were comparable between bi-layered and mixed phosphor configurations.

Conclusions:

• The bi-layered phosphor packaging scheme offers superior luminous flux and thermal characteristics compared to mixed phosphors.
• This technology enhances phosphor conversion efficiency and light extraction, leading to more efficient LEDs.
• Bi-layered phosphor white LEDs present a viable solution for general lighting, offering high efficiency and color rendering index.