Far-red-emitting SrGdAlO4:Cr3+,Bi3+ phosphors for plant growth regulation

In modern agriculture, light plays an important role in plant growth. Far red light controls the whole growth process of plants from germination to vegetative growth to flowering. Here, we report the preparation and photoluminescence (PL) performance of Cr,Bi co-doped SrGdAlO4 phosphors by solution combustion method. The SrGdAlO4:Cr3+,Bi3+ phosphors exhibit far red broadband PL of 660–780 nm excited at 458 nm, and the maximum emission peak position is at 713 nm. It was found Cr3+ and Bi3+ replaced the positions of Al3+ and Gd3+ in the host material, respectively. The PL performance of SrGdAlO4:Cr3+,Bi3+ phosphors mainly depends on the 2E2 → 4A2 transition of Cr3+, and the addition of Bi3+ can effectively enhance the PL intensity of the phosphors. Notably, the SrGdAlO4:Cr3+,Bi3+ phosphors also exhibit obvious far red PL when coated onto glass substrate or mixed with plastics without affecting their visible light transmission. We believe our work will excite interests in further exploring the practical application of SrGdAlO4:Cr3+,Bi3+ phosphors as plant growth regulator in greenhouse.