With　tunable　emission　in　the　full　visible　region,　the　ecofriendly　InP　quantum　dots　(QDs)　show　unique　application　prospects　in　light-emitting　devices.　At　present,　InP　QDs　suffer　from　wide-bandwidth　emission,　especially　for　electroluminescence　(EL),　which　hinders　their　applications　in　high-performance　display　devices.　Here,　we　report　a　facile　one-pot　synthesis　of　narrow-bandwidth　InP/ZnSeS/ZnS　QDs　using　a　safe　phosphorus　source　of　tris(dimethylamino)phosphine,　in　which　the　ZnSeS　inner-shell　layer　is　formed　via　temperature-gradient　solution　growth　from　240　to　280　°C.　The　synthesized　green　QDs　have　a　high　photoluminescence　quantum　yield　(PLQY)　of　91%　and　full　width　at　half-maximum　(fwhm)　of　36　nm.　Moreover,　the　resultant　quantum　dot　light-emitting　devices　(QLEDs)　also　show　a　narrow　fwhm　of　42　nm,　which　is　the　narrowest　emission　of　green　InP　QLEDs　based　on　a　safe　phosphorus　source　reported　so　far.　Further　modulation　of　the　electron　injection　into　the　device　by　inserting　a　thin　layer　of　lithium　fluoride　results　in　a　peak　external　quantum　efficiency　of　5.56%.　©　2023　American　Chemical　Society.