Persistent　luminescence　(PersL)　has　long　commanded　the　curiosity　of　researchers　owing　to　the　complicated　and　profound　physics　behind　it.　In　this　work,　the　PersL　mechanism　in　a　new　kind　of　persistent　garnet　phosphors,　Lu2CaMg2(Si1-xGex)3O12:Ce3+,　is　studied　from　the　new　perspective　of　a　＂solid-solution＂　scheme.　Different　from　the　conventional　study　in　pursuit　of　long　PersL,　we　focus　on　manipulation　of　afterglow　to　the　millisecond　range　and　tentatively　demonstrate　its　potential　to　compensate　the　flickering　of　the　alternating　current　driven　LED　(AC-LED)　in　every　AC　cycle.　Evidently,　the　tailored　host　bandgap　favors　efficient　electron　charging　and　facilitates　electron　detrapping,　as　well　as　redeploying　trap　distribution,　which　results　in　a　blue　light　activated　afterglow　in　the　millisecond　time　range,　and　subsequently　a　reduced　percent　flicker　of　64.1%　for　the　AC-LED.　This　investigation　is　the　first　attempt　to　establish　the　design　guidelines　for　new　PersL　materials　with　an　adjustable　millisecond　ranged　afterglow,　and,　hopefully,　it　paves　a　pathway　to　the　development　of　burgeoning　low-flickering　AC-LED　technology.　©　2016　The　Royal　Society　of　Chemistry.