QLED as a boost for indoor greenhouses

Vertical farming: The Berlin start-up Crocus Labs wants to use dynamic quantum dot LEDs to help improve the yield of indoor farms.

By Patrick Schroeder

What to do when the area for growing food becomes scarce as the world population explodes? Simply go up and grow lettuce and the like on thousands of shelves in high-rise buildings - the keyword is vertical farming. "Almost all food could be grown indoors twice as efficiently and without pesticides," says Prash Makaram, founder of the Berlin start-up Crocus Labs. But indoor farming has not yet been able to develop its full potential. Most lighting systems are inefficient and expensive. Farmers therefore often limit themselves to low-quality leafy vegetables and have difficulty becoming profitable. "We have therefore developed new types of lights, sensors and controls that optimize plant growth in indoor greenhouses and are also cost-effective," says the mechanical engineering and nanotechnology specialist with a doctorate.

Crocus Labs' lights work with so-called quantum dot light-emitting diodes (QLEDs). They work as follows: Blue LEDs are covered with a film layer into which tiny nanocrystals are incorporated. These so-called quantum dots are 2 nm to 10 nm in size and are therefore in the size range of molecules and atomic structures. The dots absorb the blue light of the LED and emit light in different colors. Small quantum dots produce short-wave light, such as green. Larger quantum dots produce long-wave light, such as red. The various QLEDs can now be used to mix colors - for example to create white light that is close to the solar spectrum so that plants grow even better.

Classic RGB LEDs reach their technical limits here because the semiconductor material indium gallium nitride, which is often used, only allows a comparatively low light output in the green spectrum. This deficit can then lead, for example, to suboptimal leaf development. Another advantage of quantum dot LEDs is that they do not require phosphor, which conventional LEDs use to convert light into different colors. Extracting the chemical is energy-intensive and usually results in environmental pollution. Recycling is also complicated.

But the QLEDs are only part of the solution. In order to increase the yield of greenhouses, Crocus Labs has developed a sensor box for the lights. Optical sensors measure the spectral composition and the intensity of the light in the environment. Software then uses this data to continuously adjust the light spectrum of the lights - for example when a cloud darkens the sky and the amount of natural red light is reduced. Thanks to intelligent control, the lights can also adapt to the growth phases of the plants. Strawberries, for example, are comparatively complicated to grow indoors. In the initial phase, they require cool light conditions with higher blue components to promote vegetative growth. In the flowering phase, however, a higher proportion of red light is required for fruit development.

"In the indoor farming sector, we are currently hardly aware of any manufacturers who offer dynamic adjustment of the light spectrum of QLEDs. Most lights only have an insulation function. Thanks to our solution, indoor farms can also grow maintenance-intensive crops and thereby increase their profitability," says Makaram. "They are also energy efficient in operation. Users can save up to 30% in energy costs compared to classic LEDs."

Crocus Labs was founded in 2020. Makaram is a serial entrepreneur who previously co-founded two medical nanosensor companies. "It was expensive and took a lot of effort to deal with German bureaucracy," says the entrepreneur. "The general lack of financing opportunities in Europe was a significant obstacle." Fortunately, the young company received funding from the European Union's EIC (European Innovation Council) and support from investors such as the Hightech Gründerfonds (HTGF), Brandenburg Kapital and BACB.

The start-up has also entered into a cooperation with the Advanced Plant Growth Centre (APGC) research centre in Scotland to further improve the technology. "For agriculture in controlled environments, light control, which includes intensity and wavelength recipes at different stages of development, is crucial if the benefits such as shorter cycles to harvest, higher productivity and improved quality and nutritional value are to be realized," says Derek Stewart, Director of APGC. "Crocus Lab's innovative LED lighting solutions offer all of these possibilities," the professor emphasizes.

The start-up is currently implementing its first pilot projects and producing the lights for them as needed. "We offer a range of spectra that range from sun-like color reproduction to precise and sharply defined wavelengths for medical applications," says Makaram. The technology could also be used in the automotive industry in the future - for example, to illuminate the interior.