Light keys open locks of plant photoresponses: A review of phosphors for plant cultivation LEDs

Light is an indispensable energy source for agricultural production. But due to the limitation of season, changeable weather and different latitude, solely relying on natural light is absolutely not enough. In order to upgrade plant photosynthesis efficiency, light emitting diode (LED) as a new generation lighting source, has become an inevitable choice to improve agricultural production efficiency. Thus a range of different phosphors for plant lighting LED (phyto-LED) are widely studied and becoming a hot topic in recent years. However, how to design acceptable plant lighting phosphors, how to evaluate suitability of synthesized phosphors and how to achieve targeted irradiation to specific plant photoreceptors are urgently clarified. The answers of these issues will be given in this review. Proceeding from relationship between light quality and photoreceptor response, we thoroughly overview recent processes on plant lighting phosphors, including their structure, frequently-used activators, characteristic excitation and emission wavelengths and photoluminescence efficiency. Importantly, we propose a quantitative method to calculate similarity between emission spectra of phosphor and plant photoreceptor absorption spectra. Finally, we address remaining challenges in this exciting field and present our perspectives for further investigations and hope that this review can be a reference for those who want to design and study phosphors for plant lighting.