Broadband　emissive　perovskites　are　next-generation　materials　for　solid-state　lighting　and　radiative　detection.　However,　white-emitting　perovskites　are　generally　synthesized　by　regulating　B/X　sites,　while　not　enough　attention　is　paid　to　the　A-site,　which　is　thought　to　hardly　affect　the　band-edge　structures　and　optoelectronic　properties.　Here,　a　series　of　Sb3+-doped　In-based　0D　halide　perovskite　derivatives　are　described　with　various　organoammonium　cations　in　A-sites.　Warm-white　light　emitting　across　the　visible　spectrum　(450–850 nm),　large　Stokes　shifts,　and　high　photoluminescence　quantum　yields　are　easily　tunable　by　molecularly　tailoring　A-site　cations.　These　features　enable　a　light　yield　up　to　60976　Photons/MeV　as　X-ray　scintillator,　and　a　detection　limit　of　90　nGyair/s　that　is　≈60　times　lower　than　the　medical　requirement.　It　is　proved　that　A-site　plays　a　critical　role　in　determining　the　degree　of　distortion　of　polyhedra,　which　influences　the　broadband　photoluminescence　and　self-trapped　exciton　(STE)　dominates　the　emission　process.　Moreover,　for　the　first　time,　via　the　incorporation　of　2,6-dimethylpiperazine,　a　mixed　A-site　regulating　strategy　produces　a　standard　white-light　emission,　which　originates　from　the　blue-light　and　yellow-light　related　to　various　STE　emission　centers.　It　is　foreseen　that　this　strategy　highlights　the　expanded　role　of　A-site　and　the　importance　of　rethinking　A-sites　in　perovskites.　©　2023　Wiley-VCH　GmbH.