Solid State Lighting for horticolture: impact of LED reliability on light spectrum and intensity

This paper reports on the analysis of the degradation of high-power light-emitting diodes (LEDs) for horticulture lighting applications. The study is based on the experimental characterization of state-of-the-art red and blue commercial off-the-shelf LEDs from the same product-line and the same manufacturer. In this work we report that the degradation kinetic of photo-red (660nm) LEDs subjected to accelerated stress is faster with respect to its blue LEDs (450nm) counterpart. In particular we describe a more evident electrical degradation for the blue LEDs and a more prominent Optical Power (OP) decrease for red LEDs. A differential degradation is then causing a gradual variation of the emitted spectrum. Finally, the intensity of the spectral variation and its effect on the efficacy of the lamp is analyzed in view of the results reported in the literature for red-blue horticulture lighting for different applications.