What is a full spectrum LED growth lamp?

2019-09-06

LED growth lamp technology is relatively new. One of the advantages is the ability to generate a variety of different emission spectra.

In this article, we will discuss what constitutes a full-spectrum LED growth lamp and whether they are beneficial for plant growth.

What is the traditional LED growth spectrum?

Conventional growth LED growth lamps typically use a combination of blue and red LEDs. You can usually judge by the purple-red light emitted - this is the result of mixing blue and red light.

Conventional LED growth lamps use this formulation because plants are most effective for photosynthesis in the blue and red portions of the spectrum.

However, observing this spectrum clearly covers only a small portion of the entire visible spectrum. This is definitely not the full spectrum we are talking about.

Typically, these growth lamps use a single color LED - a blue LED and a red LED. You can usually judge by looking at its spectral power distribution as follows:

But if blue and red light are the best way to promote photosynthesis, why do we care about other wavelengths?

The answer is that there are other processes that affect plant health and vitality, not just the extent to which photosynthesis occurs. Ultimately, this could mean higher quality crops, better aesthetics or higher nutrients. In other words, quality is more than just quantity.

Strict definition of full spectrum LED growth illumination

A lot of research is still needed, but the results of experiments and studies are increasing, indicating that plants grow best under equilibrium spectra.

This can be explained by the fact that plants have evolved to use natural sunlight not only as a food source but also as a signal for flowering and fruit production.

Therefore, a strict definition of the full spectrum will require a spectrum of energy from the ultraviolet to the infrared, just like natural daylight.

Light sources with this spectrum typically appear white. If the LED growth light emits white light, will it automatically make it a full-spectrum growth light?

The answer is no, we will discuss it further in the next section.

Different ways of creating white light

Unlike conventional LED growth lamp methods for blue and red monochromatic LEDs, full-spectrum growth lamps typically use a phosphor coating.

The reason that the phosphor coating contributes to the full spectrum of light growth is that the phosphor takes light from a single narrow wavelength range (eg, 460 nm blue) and converts it into a wide range of longer wavelength light (eg, 600-700 nm red).

By coating the blue LED with a mixture of green, yellow and/or red phosphors, a wider coverage in the visible spectrum can be achieved.

Because the light emitted by the phosphor has many different wavelengths, a balanced color mixing is produced, resulting in white light.

Just because LED growth light emits white light does not necessarily mean it is a true full spectrum source.

A convenient method is to evaluate its color rendering index (CRI). This is a useful indicator because it tells us how similar it is to natural daylight. A higher CRI rating indicates that the source is more similar to natural daylight, which is the ideal full spectrum source.