Over　the　past　few　years,　light-emitting　diodes　(LEDs)　have　emerged　as　an　efficient　replacement　for　standard　incandescent　and　fluorescent　lamps,　due　to　their　superior　efficiency,　energy　conservation,　service　longevity,　reliability,　and　affordability.　However,　identifying　a　red　emitter　for　white　LEDs　has　presented　significant　challenges.　This　study　seeks　to　synthesize　and　analyze　a　novel　red　emitter,　investigating　its　potential　use　in　white　LEDs　and　indoor　plant　growth　lighting.　The　Sr2Lu(Nb,Mn)O6　is　manufactured　employing　the　traditional　high-temperature　solid-phase　method.　The　internal　and　external　quantum　efficiencies　(IQE　and　EQE)　of　double　perovskites　reached　32.39%　and　21.67%.　The　g　value　calculates　to　2.146,　which　corroborates　that　the　magnetic　dipolar　transitions　of　Mn4+　ions　inhabit　symmetric　octahedral　sites.　First-principles　investigations　are　utilized　to　unveil　local　electronic　structures.　Emission　spectra　reveal　a　substantial　broad　red　emission　peak　at　688 nm.　The　Tanabe–Sugano　diagram　is　applied　to　understand　the　luminescence　mechanism.　Additionally,　the　evaluation　of　parameters　such　as　the　internal　UV　emission　ratio,　crystal　field　strength,　and　Racah　parameters　is　conducted.　The　luminescent　intensity　of　the　Sr2Lu(Nb,Mn)O6　can　still　be　maintained　at　60%　upon　reaching　a　temperature　of　423 K.　The　findings　suggest　that　Sr2Lu(Nb,Mn)O6　offers　a　novel　alternative　for　white　LEDs　and　indoor　plant　growth　lighting.　©　2024　Wiley-VCH　GmbH.