The Sr3SiO5:Eu2+ phosphor has attracted considerable attention for applications in white LEDs owing to its highly efficient yellow emission under violet-blue excitation. We report herein an enhancement of yellow persistent luminescence in Sr3SiO5:Eu2+ through Ge incorporation. The strongest persistent luminescence intensity is observed for Sr-3(Si1-xGex)O-5 :Eu2+ with x = 0.005 with a peak emission wavelength at similar to 580 nm and a persistent time of similar to 7000 s at the 0.32 mcd/m(2) threshold value after UV radiation. A combination of thermoluminescence measurements and density functional theory (DFT) calculations reveals that the afterglow enhancement is due to a significant increase in the number of oxygen vacancies that act as electron trapping centers with appropriate trap depths. This investigation is anticipated to encourage more exploration of Ge-Si substitution to design and improve Si-containing persistent phosphors with superior functionalities.