Photoluminescence characteristics and energy transfer between Bi³⁺ and Eu³⁺ in Na₂O–CaO–GeO₂–SiO₂ glass

We report the photoluminescence (PL) of Eu³⁺-doped glass with Bi³⁺ as a sensitizer. The specific glass system with the strong enhancement of the red emission of Eu³⁺ is obtained by adding a small number of Bi³⁺ ions instead of increasing the Eu³⁺ concentration. The emission band of Bi³⁺ overlaps with the excitation band of Eu³⁺ and the lifetime decay curves, resulting in a very efficient energy transfer from Bi³⁺ to Eu³⁺. The probability of energy transfer is strongly dependent on Bi³⁺ concentration. In addition, the intensity of 4f–4f transition is much stronger than that of a charge-transfer (CT) band in the excitation spectrum, which indicates that the Na₂O–CaO–GeO₂-SiO₂ glass is a suitable red-emitting phosphor with high stability as a candidate for light-emitting diodes (LEDs).