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Light emitting diodes as a plant lighting sourceElectroluminescence in solid materials is defined as the generation of light by the passage of an electric current through a body of solid material under an applied electric field. A specific type of electroluminescence, first noted in 1923, involves the generation of photons when electrons are passed through a p-n junction of certain solid materials (junction of a n-type semiconductor, an electron donor, and a p-type semiconductor, an electron acceptor). The development of this light emitting semiconductor technology dates back less than 30 years. During this period of time, the LED has evolved from a rare and expensive light generating device to one of the most widely used electronic components. A number of LED characteristics are of considerable importance in selecting a light source for plant lighting in a controlled environment facility. Of particular importance is the characteristic that light is generated by an LED at a rate far greater than the corresponding thermal radiation predicted by the bulk temperature of the device as defined by Plank's radiation law. This is in sharp contrast to other light sources, such as an incandescent or high intensity discharge lamp. A plant lighting system for controlled environments must provide plants with an adequate flux of photosynthetically active radiation, plus providing photons in the spectral regions that are involved in the photomorphogenic and phototropic responses that result in normal plant growth and development. Use of light sources that emit photons over a broad spectral range generally meet these two lighting requirements. Since the LED's emit over specific spectral regions, they must be carefully selected so that the levels of photsynthetically active and photomorphogenic and phototropic radiation meet these plant requirements.
Document ID
19960011713
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Bula, R. J.
(Wisconsin Univ. Madison, WI, United States)
Tennessen, D. J.
(Wisconsin Univ. Madison, WI, United States)
Morrow, R. C.
(Wisconsin Univ. Madison, WI, United States)
Tibbitts, T. W.
(Wisconsin Univ. Madison, WI, United States)
Date Acquired
September 6, 2013
Publication Date
March 1, 1994
Publication Information
Publication: International Lighting in Controlled Environments Workshop
Subject Category
Life Sciences (General)
Accession Number
96N18149
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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