Everything You Need to Know About “Full-Spectrum” LED Technology

Full-spectrum LED technology has become a buzzword in recent years, especially when it comes to emulating natural sunlight and improving the quality of light. In this article, we’ll dive into the world of full-spectrum LEDs, how they came about, how they’re made, and where they’re used. We’ll talk about how you can achieve full-spectrum LEDs with different chip and phosphor combinations, the challenges of making them, and how they’re showing up in products like desk lamps, industrial lighting, and even plant growth lights. Finally, we’ll answer the question, “Do you really need full-spectrum lighting?” and “How can full-spectrum lighting benefit you in your environment?”

The Definition of “Full-Spectrum” LEDs

When we talk about the popular “full-spectrum” LEDs today, it’s important to clarify what “full-spectrum” means. True “full-spectrum” refers to light emitted from a source that covers the entire spectrum from ultraviolet (UV), visible light, to infrared (IR), mimicking the full spectrum of sunlight (as shown in Figure 1).

This is the most comprehensive “full-spectrum” found in nature. However, the “full-spectrum” LED most people talk about today is a narrower definition. In the LED context, “full-spectrum” refers to light emitted within the visible light range that closely resembles the spectrum of sunlight in that same range (as shown in Figure 2).

The ultraviolet and infrared parts are excluded, mainly to make full-spectrum LEDs more feasible for mass production. Adding UV and IR would complicate the whole packaging system and application, making large-scale production and practical use nearly impossible. Even with only the visible spectrum included, it is not easy to achieve full-spectrum LEDs. For example, to achieve a high color rendering index (CRI) close to 100, many companies struggle to improve the CRI from 96 to 98, let alone achieving 99 or higher.

full spectrum of sunlight

Figure 1: Full spectrum of sunlight (280nm-4000nm)

sunlight spectrum within the visible range

Figure 2: Sunlight spectrum within the visible range (380nm-780nm)

How To Achieve Full-Spectrum LEDs

In theory, there are two main ways to achieve full-spectrum LEDs: one is by using chips and the other is by using phosphors. On the chip side, there are two main ways: one is the chip exciting the phosphor, and the other is using the chip alone without phosphor. On the phosphor side, you need to pair the phosphors with the chip, and you need to select different emission and excitation wavelengths for the combination. In total, there are four main ways to achieve full-spectrum LEDs:

how to achieve full spectrum leds

1. Single-band Blue Chip Exciting Phosphors

This method is similar to ordinary LED packaging, but multiple phosphors are added (e.g., green, yellow, red, or even orange, cyan, blue). Although this can produce light close to full-spectrum, there is still a prominent blue light peak. Furthermore, the efficiency of phosphors like cyan and blue is relatively low, and light in the 470-510nm range may be missing.

2. Dual-band or Triple-band Blue Chip Exciting Phosphors

This method improves on the single-band approach by using a dual-band or triple-band blue chip to excite phosphors across different wavelengths. The dual-band chips typically use two ranges: 430-450nm and 460-480nm, while the triple-band chips use three: 430-440nm, 440-460nm, and 460-480nm. This allows more flexibility in pairing the chips with phosphors to better match the sunlight spectrum (as shown in Figure 3). With this approach, CRI can exceed 98. However, this method requires a wide variety of phosphors, making it harder to ensure consistency and stability during mass production.

spectrum of dual band and triple band blue light full spectrum leds

Figure 3: Spectrum of dual-band and triple-band blue light full-spectrum LEDs (for reference)

3. UV Chip Exciting Phosphors

This method has lower light efficiency. The main reason is that most commercially available phosphors are designed to work with blue chips, not UV chips, so their excitation efficiency is much lower in the UV range. Additionally, UV chips typically range from 385-405nm, which also have lower efficiency. Although UV chips can more closely mimic the sunlight spectrum and avoid the presence of short-wavelength blue light (as shown in Figure 4), this method has drawbacks. For instance, UV chips cause more significant degradation of phosphors over time, resulting in color shifts and color temperature issues. UV light also damages organic materials like encapsulants, reducing the LED’s lifespan.

spectrum of uv full spectrum leds

Figure 4: Spectrum of UV full-spectrum LEDs (for reference)

4. Multi-chip Combination Method

This method combines chips emitting blue, cyan, green, yellow, and red light to achieve a full spectrum. While this can work in theory, it is less commonly used due to several challenges. For one, chips emit light with narrow bandwidths, making it difficult to achieve the broader spectrum that phosphors provide. Additionally, the efficiency of different colored chips varies greatly, making it challenging to balance the light output. Over time, color shifts and temperature changes may also occur due to the differing degradation rates of chips.

To provide a clearer comparison, the following table summarizes the four methods of achieving full-spectrum LEDs:

MethodEfficiencyCRICostPackaging DifficultyOverall PerformanceMethod Type
Single-band Blue Chip Exciting PhosphorsHighModerateLowLowGoodChip Excites Phosphors
Dual/Triple-band Blue Chip Exciting PhosphorsHighHighModerateModerateVery GoodChip Excites Phosphors
UV Chip Exciting PhosphorsLowHighHighLowPoorChip Excites Phosphors
Multi-chip CombinationLowHighHighLowPoorChip (Can Add Phosphors)

Applications of Full-Spectrum LEDs

Now that we’ve covered the methods for achieving full-spectrum LEDs, how can we effectively apply them? One key consideration is color temperature. Sunlight changes throughout the day and across seasons. For example, the color temperature at sunrise is around 2000K, at noon it’s around 5000K, and at sunset it’s about 2300K. Therefore, full-spectrum LEDs need to be designed to mimic the corresponding sunlight spectrum at different color temperatures, which can be achieved using the methods described above.

applications of full spectrum leds

Based on the above explanation, full-spectrum LEDs can be used in nearly any standard lighting fixture, such as household lighting, outdoor lighting, industrial lighting, desk lamps, full spectrum led strips and even plant lighting. Specific applications depend largely on price and consumer acceptance. Currently, desk lamps are the most common application, often marketed as low-blue light, eye-protecting, and color-temperature adjustable. These lamps are priced higher than standard lamps. The comparison between Chinese national standards and the “full-spectrum certification” CRI requirements is shown in Table 2. As seen in the table, the Chinese national standard for desk lamps can be easily met by ordinary LED light sources, while the full-spectrum certification requires more advanced performance.

Table 2: CRI Comparison for Desk Lamps

StandardFull-Spectrum Certification
Standard Number & NameGB/T 9473-2022 “Performance Requirements for Reading and Writing Lamps”
CRI RequirementsGeneral CRI: Ra ≥ 80
Special CRI: R9 > 0

Conclusion

Based on the above introduction to full-spectrum LED technology, we, as industry professionals, need to think about: Is the current “full-spectrum” light source something that people really need? Please feel free to message me or leave comments for further discussion!

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