Plant growth gets the red light from Showa Denko

April 7, 2009
The Japanese LED maker has developed high-performance 660 nm chips that accelerate plant photosynthesis.
Showa Denko K.K., a Japan-based LED maker, has started selling samples of AlGaInP (aluminum gallium indium phosphide) LED chips that emit red light with wavelength of 660 nm. This, says the company, is the optimum light for accelerating the growth of plants.
Red light stimulates plants Showa Denko has developed a new light-emitting layer and claims to have achieved an output of 11 mW at the drive current of 20 mA, which is believes to the world’s highest level for 660-nm LED chips to date.

In recent years, there has been widespread investigation of the growth of vegetables under conditions where various aspects of the environment are controlled, such as lighting, temperature, humidity, CO2 concentration and nourishment.

Nearly 30 facilities of this kind are already in operation in Japan. They ensure stabilized production regardless of season or location; they allow multiple harvests; and they do not need fungicides or insecticides because of the controlled environment.

It has been found that red light with wavelengths of around 660 nm is most effective in increasing the efficiency of photosynthesis, thereby accelerating the growth of plants. Fluorescent lamps, sodium lamps, and conventional red LED lamps are now used at plant growth facilities.

However, fluorescent and sodium lamps emit a great deal of light with wavelengths other than around 660 nm, resulting in energy loss and high costs. Conventional red LED lamps need to use many chips because of their low output, which is also costly. Furthermore, the wavelength of conventional AlGaInP LED chips is 650 nm at best, falling short of the ideal wavelength of 660 nm.

In addition to the development of the new 660-nm-light-emitting layer, Showa Denko says it has improved the shape and arrangement of electrodes as well as the chip surface treatment method. Thus, the external quantum efficiency of LED lamps using the new AlGaInP chips is about three times as high as that of conventional red LED lamps.

Compared with the conventional red LED lamps, the new AlGaInP LED lamps reduce electric power consumption by 70% at a given level of brightness, resulting in lower costs and energy consumption at plant growth facilities. Lower heat emission from light sources will also improve the plant growth environment.