Enhanced photoluminescence of K7CaY2(B5O10)3:Eu3+,Sm3+/Gd3+ phosphors through energy transfer and their applications in LED lights for plant growth

Abstract

A series of K7CaY2−x(B5O10)3:xEu3+ (KCYB:xEu3+) phosphors have been successfully synthesized using a high-temperature solid-state method, while Sm3+ and Gd3+ ions were co-doped to enhance the luminous performance. The crystal structure and occupation position of Eu3+/Sm3+/Gd3+ in the borate K7CaY2(B5O10)3 host were investigated by XRD technique and Rietveld refinement data analysis. Under the characteristic excitation of Sm3+/Gd3+, it was found that the luminescence intensity of Eu3+ could considerably increase due to the energy transfer from Sm3+/Gd3+ to Eu3+ in KCYB, which was also increased even under 393 nm excitation (transition of Eu3+). To evaluate the sensitization of Sm3+/Gd3+ to Eu3+, the doping contents of Sm3+ and Gd3+ ions were fixed. The photoluminescence performance and lifetime decay curves of all co-doped samples were tested. The higher energy transfer efficiencies for Sm- and Gd-doped KCYB:Eu3+ phosphors reached 31.45% and 57.49%, respectively. The dipole-dipole interaction has been demonstrated to be the dominant energy transfer mechanism. KCYB:Eu3+,Sm3+/Gd3+ phosphors exhibit red light emission at 610 nm with a high quantum yield (86.98%) and color purity (100%), good thermal stability (57.97%@473 K), and the emission spectra lie within the red photopigments (PR) absorption spectra of plants. These results show that the prepared K7CaY2(B5O10)3:Eu3+,Sm3+/Gd3+ phosphors may provide promising options for red phosphors in plant lighting applications.