(INVITED) Exploring Sm2+ activated phosphors as red-deep red photon generator for horticultural application

The red (600 nm–700 nm) and far-red (FR; 700 nm–750 nm) wavelengths of the electromagnetic spectrum are important for plant growth. Phosphors can be used to down-convert the blue emission of the InGaN LED to red and FR light for use in horticultural lighting. In the archival literature, investigations pertaining to the development of such phosphors are primarily concerned with studies of the photoluminescence of transition metal (Mn4+ and Cr3+) and rare earth (Eu2+) ions. In this work we explore the spectroscopic properties of the divalent samarium (Sm2+) ion for usage in LED based horticultural lighting device. We show that both the inter- and intraconfigurational emission transitions of the Sm2+ ion can provide efficient stimulation of the phytochromes. Factors that determine the nature of emission are discussed as are the general mechanistic aspects of thermal quenching and quantum efficiency of luminescence.