Commercially available LEDs come in a wide range of colors, spanning the visible spectrum, as well as ultraviolet (UV) and infrared (IR) wavelengths. The color of light emitted by an LED depends on the semiconductor material used and the energy gap between the electron and hole recombination in the LED’s p-n junction. Here are the common colors of LEDs available in the market:
1. Visible Spectrum LEDs:
- Red (620โ750 nm):
- Red LEDs are one of the earliest and most common colors available. They are typically made using gallium arsenide (GaAs) or aluminum gallium arsenide (AlGaAs).
- Applications: Indicators, traffic lights, signs, and display systems.
- Orange/Amber (590โ620 nm):
- Orange or amber LEDs are commonly used in signaling and displays. These are usually made with gallium arsenide phosphide (GaAsP) or aluminum indium gallium phosphide (AlInGaP).
- Applications: Automotive lights, signage, and decorative lighting.
- Yellow (570โ590 nm):
- Yellow LEDs are less common but are available for various signaling applications. They are also made from AlInGaP.
- Applications: Indicators, displays, and backlighting.
- Green (495โ570 nm):
- Green LEDs have become more efficient with advances in indium gallium nitride (InGaN) technology. Older versions used gallium phosphide (GaP) or AlGaP but were less bright.
- Applications: Traffic lights, indicators, and backlighting.
- Blue (450โ495 nm):
- Blue LEDs are made from gallium nitride (GaN) or indium gallium nitride (InGaN). The development of blue LEDs was a major breakthrough in the 1990s, enabling the creation of white LEDs.
- Applications: Backlighting, indicators, displays, and part of white LED technology (when combined with phosphor).
- Violet (~400โ450 nm):
- Violet LEDs emit a light that is closer to the ultraviolet spectrum. They are typically made from GaN or InGaN.
- Applications: Special lighting, decorative lighting, and scientific instruments.
2. White LEDs:
- White LEDs are not true single-wavelength emitters. They are typically created using one of two methods:
- Phosphor-converted white LEDs (PC-LEDs): A blue or ultraviolet LED excites a phosphor coating, which emits yellow light. The combination of the blue LED light and the yellow phosphor creates the appearance of white light.
- RGB White LEDs: A combination of red, green, and blue LEDs can be used to create white light by adjusting the intensities of each color.
- Applications: General lighting, display backlighting, flashlights, automotive lights, and more.
3. Ultraviolet (UV) LEDs:
- UV-A LEDs (320โ400 nm):
- These LEDs are commonly used in applications where long-wave UV light is required. They are made from GaN or InGaN materials.
- Applications: Curing (e.g., adhesives, coatings), counterfeit detection, sterilization, and blacklight effects.
- UV-C LEDs (100โ280 nm):
- UV-C LEDs produce deep ultraviolet light and are typically used for sterilization and disinfection because UV-C light has germicidal properties.
- Applications: Water purification, air sterilization, and surface disinfection.
4. Infrared (IR) LEDs:
- Near-Infrared (NIR) LEDs (700โ1000 nm):
- IR LEDs are widely used in remote controls, night vision cameras, and IR communication systems. These LEDs are made from gallium arsenide (GaAs) or aluminum gallium arsenide (AlGaAs).
- Applications: Remote controls, security systems, IR sensing, and communication.
Specialty LED Colors:
- Pink: Typically achieved by combining white LEDs with a red filter or by mixing red and blue LEDs.
- Purple: A combination of red and blue LEDs or violet LEDs emitting at the appropriate wavelength.
- Warm White/Cool White: These are variations of white LEDs, where different phosphor coatings adjust the color temperature. Warm white LEDs have a yellowish hue (2700K to 3000K), while cool white LEDs have a bluish tint (5000K to 6500K).
Summary of Commercially Available LED Colors:
- Red: (620โ750 nm)
- Orange/Amber: (590โ620 nm)
- Yellow: (570โ590 nm)
- Green: (495โ570 nm)
- Blue: (450โ495 nm)
- Violet: (400โ450 nm)
- White: (phosphor-coated blue LEDs or RGB combinations)
- Ultraviolet (UV): UV-A, UV-B, and UV-C
- Infrared (IR): 700โ1000 nm (near-infrared)
Applications of LED Colors:
- White LEDs dominate in general lighting, backlighting, and flashlights.
- Red, Green, and Blue LEDs are widely used in display technologies (RGB LEDs).
- Infrared and UV LEDs have specialized uses in communications, medical applications, disinfection, and sensing.
The wide variety of colors available in LEDs, including white, UV, and IR, allows for a vast range of applications, from general illumination to specialized scientific and industrial uses.