Design of vertically-stacked polychromatic light-emitting diodes

Area of Science:

• Solid-state lighting
• Optoelectronics
• Materials science

Background:

• Traditional light-emitting diodes (LEDs) often rely on phosphors for white light generation, which can impact color quality and efficiency.
• Achieving tunable, high-quality polychromatic light from a single device presents engineering challenges.

Purpose of the Study:

• To propose and demonstrate a new design for a polychromatic light-emitting diode (LED).
• To enable natural color mixing within the LED structure without external optical components.
• To develop a phosphor-free white light LED with high luminous efficacy and color tunability.

Main Methods:

• Physically stacking LED chips of primary colors (red, green, blue) in a layered structure.
• Utilizing the inherent light propagation and mixing as light passes through adjacent layers.
• Characterizing the spectral output and luminous efficacy of the stacked LED device.

Main Results:

• Demonstration of a stacked polychromatic LED design.
• Natural light mixing achieved through the physical arrangement of primary color LED chips.
• Generation of a wide range of colors, suitable for display applications.
• Achieved luminous efficacy of 30 lm/watt for the phosphor-free white light LED configuration.

Conclusions:

• The proposed stacked LED design offers a viable method for creating polychromatic and white light.
• This approach eliminates the need for additional optics for color mixing, simplifying device architecture.
• The phosphor-free white light LED demonstrates promising performance for display and general illumination applications.