In　this　work,　two　spiro‐type　compounds　are　investigated　with　similar　molecular　structure　and　stacking　structure.　By　simply　altering　the　acceptor＇s　heteroatoms,　a　strategy　to　enhance　room　temperature　phosphorescence　(RTP)　performance　is　presented.　The　intersystem　crossing　process 　can　effectively　be　accelerated　by　reducing　the　energy　gap　between　the　singlet　and　triplet　states　(ΔEST)　through　adjusting　the　molecular　energy　level.　Besides,　thermally　activated　delayed　fluorescence　(TADF)　is　emerging　in　dilute　solution　due　to　such　small　ΔEST.　This　is　helpful　for　deeply　understanding　the　mechanism　of　competition　in　different　radiative　decay　pathways　(RTP　and　TADF).