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

•A Facile and efficient strategy has been used to synthesize the far-red phosphor.•Energy transfer has been verified by measuring 3D photoluminescence spectra.•The sensitizer has assisted in doubling the quantum efficiency.•The phosphor synthesized herein exhibited outstanding thermal and photostability.•The fabricated LED with NUV chip exhibited high-purity far-red emission.