Rationalized crystal structure augmented highly efficient far-red-emitting double perovskite niobate phosphor for indoor plant growth LED applications

Since the inception of white light-emitting diodes (white LEDs), phosphor-coated LEDs have been in focus owing to the tremendous advantageous that they offer in assorted applications ranging from biomedical to automotive applications, including plant growth. While, plant growth LEDs have been bustling the commercial market, there is ample scope to commercialize the promising far-red (FR) emitting LEDs for potential growth of plants in indoor farming. Herein, a facile and efficient strategy was used to develop Mn4+ (Nb site)- and Sm3+ (La site)- ions-doped Ca2LaNbO6 (CLNO:Mn4+/Sm3+) phosphors with outstanding photoluminescence (PL) properties. The PL properties of CLNO:Mn4+ and CLNO:Sm3+ phosphors showed FR emissions at 650 and 697 nm, respectively. When Mn4+/Sm3+ ions were co-doped in a CLNO host lattice, Rietveld refinement revealed alterations in bond lengths of the CLNO crystal structure, which enhanced the phosphor’s thermal stability and photostability and caused the creation of effective pathways for efficient energy transfer from Sm3+ to Mn4+ ions. Furthermore, the reverse strategy, where the sensitizer (Sm3+) concentration was changed instead of activator (Mn4+) concentration, was used to achieve brilliant FR emission from the CLNO:Mn4+/Sm3+ phosphors and the dominant emission was perceived for the CLNO:0.2Mn4+/1.5Sm3+ phosphor. The internal quantum efficiency of the CLNO:0.2Mn4+/1.5Sm3+ phosphor was increased from 28% (CLNO:0.2Mn4+) to 56%. An LED fabricated by coating a CLNO:Mn4+/Sm3+ phosphor layer on a near-ultraviolet LED chip exhibited excellent FR emission with high color purity and with chromaticity coordinates of (0.733, 0.267). The results obtained for the CLNO:0.2Mn4+/1.5Sm3+ phosphor along with the characteristics of fabricated LED showed the high potential of the phosphor for use in promoting indoor plant growth.