Comparative evaluation of the photosynthetic photonic efficiency of white LEDs

Abstract

White LEDs are an effective solution for light culture due to the presence of the green emission spectrum, which has a positive effect on growing plants in the artificial environment. However, the assessment of the effectiveness of the application of the white LEDs for photoculture is complicated by the lack of information in the technical documentation for LEDs about their photosynthetic photon flux in the range of photosynthetically active radiation. In this regard, the purpose was to measure the photonic and energy characteristics of popular white LEDs in various operating modes and to evaluate their photosynthetic photonic efficiency. High-demand brands of LEDs of the rated power of 0.5W in SMD2835 and SMD3030 housing were selected to be studied. The luminous flux of LEDs was measured using a luminous flux meter using the “integrating sphere” method, and then their luminous efficiency and photosynthetic photonic efficiency were calculated. The highest photosynthetic radiation efficiency (more than 2.7 μmol s−1) was registered for LEDs of the color temperature of 4000K and 5000K in the SMD3030 housing, manufactured using flip-chip technology. LEDs of the color temperature of less than 3000K have the lowest photosynthetic photonic efficiency, which is primarily associated with the energy losses in the phosphor and the presence of radiation in the far-red spectrum region, which is not included in the region of photosynthetically active radiation. White LEDs can be used both separately and in combination with the red and blue LEDs, which will allow selecting the spectral composition of the radiation for the specific species and variety of plants.