How Luminescent Materials Are Different Than Filters

Filters

A colored light filter works by selectively absorbing or transmitting certain wavelengths of light. The filter has a material with pigments or dyes that absorb specific wavelengths of light, allowing others to pass through. The plant absorbs light and converts it into heat energy, dissipating it into the environment. This is because the pigments or dyes in the filter vibrate at the same frequency as red light. As a result, they absorb and release the energy. The filter transmits only red light as a result.

The amount of light lost through a colored filter depends on several factors. These factors include the type, thickness, and filtered light wavelengths. Still, the range of light loss is typically 40-80%. The filter’s color intensity directly correlates with the amount of lost light intensity.

For example, a deep red filter will absorb more light than a light pink filter. The thickness of the filter also plays a role in how much light intensity is lost. Thicker filters absorb more light than thinner filters, as they have a greater volume for the light to interact with.

The amount of light intensity lost is also influenced by the specific wavelengths of light being filtered. For example, if a green filter filters out blue light, less light intensity will be lost than if the same green filter is used to filter out red light, as green filters are less effective at absorbing red light.

It is important to note that while some light intensity is lost through a colored filter, the transmitted light’s quality (or color spectrum) is changed. For example, a blue filter will reduce overall light intensity but enhance the concentration of exposure to blue light in the spectrum, which can benefit specific applications such as plant growth or photography.

Figure 1. Filters absorb light and convert it to heat. Fluorophores absorb light and convert it to lower energy light or a redder color.

Luminescent Materials

In contrast, a luminescent material, or fluorophore, emits light through fluorescence or phosphorescence. When these materials are exposed to light, they absorb the light energy and then emit light of a longer wavelength (lower energy). This is why they are sometimes called “glowing” materials or “light conversion materials.”

Quantum dots, dyes, and phosphors are examples of colored luminescent materials that can be used in cover materials for a greenhouse. They can be used to alter the spectrum of light that enters the greenhouse, which can impact plant growth and development.

For example, quantum dots can be used to adjust the spectral composition of sunlight to match the specific needs of different plants. By changing the size and composition of the quantum dots, it is possible to tune their absorption and emission spectra, allowing them to absorb and emit light in specific wavelength ranges. To learn more about light interaction with plants, check out our blog, Light Interaction with Plants: Reflection, Emission, and Absorption.