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    Critical Thought

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    New Technology Enables Highly Efficient Green LEDs with Lower Indium Content

    BySam Figg

    Feb 5, 2024
    New Technology Enables Highly Efficient Green LEDs with Lower Indium Content

    Color mixing, the process of combining different colors to create new ones, is the foundation of solid-state lighting. Currently, white light is achieved through phosphor down-conversion, but LED color mixing has the potential for higher efficiency. However, there is a significant challenge in achieving efficient green LEDs, known as the “green gap.”

    Researchers at the University of Illinois Urbana-Champaign have made a groundbreaking discovery in their quest to fill the green gap. They have successfully developed a green-emitting cubic III-nitride active layer with an internal quantum efficiency (IQE) of 32%, which is more than 6 times higher than conventional cubic active layers.

    The ultimate goal is to triple the efficiency of today’s white LEDs, and filling the green gap is a crucial step towards achieving that. By using cubic nitrides, the researchers showcase the innovation from the materials side.

    The most efficient white LEDs currently use blue light emitting diodes with a phosphor coating that converts the blue light into yellow, green, and/or red, enabling white lighting. However, this phosphor down-conversion process has limitations. It is inherently inefficient because high energy photons have to lose energy to be converted into photons of other energies. Additionally, the process generates a significant amount of heat.

    The researchers found a way to synthesize low defect density, high-quality cubic gallium nitride by utilizing an aspect ratio phase trapping technique. This technique allows the surface of the active layer to be a perfect cubic-phase material, trapping defects and undesirable hexagonal phases.

    With their cubic III-nitride system, the researchers achieved highly efficient, droop-free green LEDs with a 32% IQE and only 16% indium content. This is a significant accomplishment considering the traditional hexagonal well requires a higher indium content for green emission.

    By using cubic III-nitride, the green gap can be closed, as these materials offer advantages in solid-state lighting. The research team’s novel aspect ratio phase trapping technique ensures high-quality, pure cubic III-nitride.

    This breakthrough in LED technology brings us a step closer to achieving more efficient and sustainable lighting solutions. The use of lower indium content not only improves efficiency but also reduces costs associated with raw materials and packaging. With further advancements in LED color mixing, we can expect to see even greater energy efficiency in the future.

    FAQ:

    1. What is color mixing?
    – Color mixing is the process of combining different colors to create new ones.

    2. How is white light currently achieved in solid-state lighting?
    – Currently, white light is achieved through phosphor down-conversion, where blue light emitting diodes with a phosphor coating convert the blue light into yellow, green, and/or red, resulting in white lighting.

    3. What is the “green gap” in LED color mixing?
    – The “green gap” refers to the challenge of achieving efficient green LEDs. Green LEDs have lower efficiency compared to other colors, making it difficult to improve overall efficiency in white LEDs.

    4. What has been the groundbreaking discovery made by researchers at the University of Illinois Urbana-Champaign?
    – The researchers have successfully developed a green-emitting cubic III-nitride active layer with an internal quantum efficiency (IQE) of 32%, which is more than 6 times higher than conventional cubic active layers. This is a significant step towards filling the green gap.

    5. How do cubic III-nitrides contribute to improving LED efficiency?
    – By using cubic nitrides, the researchers are able to showcase innovation from the materials side. Cubic III-nitrides offer advantages in solid-state lighting and can help close the green gap in LED color mixing.

    Key Terms:
    – Color mixing: The process of combining different colors to create new ones.
    – Phosphor down-conversion: The process of converting high energy photons into photons of other energies using a phosphor coating.
    – Internal quantum efficiency (IQE): A measure of how efficiently a light-emitting diode converts electrons into photons.

    Related Links:
    University of Illinois Urbana-Champaign
    Energy.gov: Lighting Choices
    Energy.gov: Basic Energy Sciences