Self-enhanced　electrochemiluminescence　(ECL)　probes　have　attracted　more　and　more　attention　in　analytical　chemistry　for　their　significant　simplification　of　the　ECL　sensing　operation　while　improving　the　ECL　sensing　sensitivity.　However,　the　development　and　applications　of　self-enhanced　ECL　probes　are　still　in　their　infancy　and　mainly　suffer　from　the　requirement　of　a　complicated　synthesis　strategy　and　relatively　low　self-enhanced　ECL　activity.　In　this　work,　we　took　advantage　of　the　recently　emerged　perovskite　quantum　dots　(PQDs)　with　high　optical　quantum　yields　and　easy　surface　engineering　to　develop　a　new　type　of　PQD-based　self-enhanced　ECL　system.　The　long　alkyl　chain　(C18)　diethanolamine　(i.e.,　N-octadecyldiethanolamine　(ODA))　with　high　ECL　coreactant　activity　was　selected　as　a　capping　ligand　to　synthesize　an　ODA-capped　PQD　self-enhanced　ECL　probe.　The　preparation　of　the　coreactant-capped　PQDs　is　as　simple　as　for　the　ordinary　oleylamine　(OAm)-capped　PQDs,　and　the　obtained　ODA-capped　PQDs　exhibit　very　strong　self-enhanced　ECL　activity,　82.5　times　higher　than　that　of　traditional　OAm-capped　PQDs.　Furthermore,　the　prepared　ODA-PQDs　have　a　unique　nanostructure　(ODA-CsPbBr3@CsPb2Br5),　with　the　highly　emissive　3D　CsPbBr3　PQD　as　the　core　and　the　water-stable　2D　CsPb2Br5　as　the　shell,　which　allows　ODA-PQDs　to　be　very　stable　in　aqueous　media.　It　is　envisioned　that　the　prepared　ODA-3D@2D　PQDs　with　the　easy　preparation　method,　strong　self-enhanced　ECL,　and　excellent　water　stability　have　promising　applications　in　ECL　sensing.　©　2024　American　Chemical　Society.