Coinage　metal　clusters　are　a　promisingclass　of　X-ray　scintillatorsto　substitute　for　traditional　commercial　ones　in　X-ray　imaging　dueto　their　comprehensive　advantage.　X-ray　scintillatorsare　widely　used　in　medical　imaging,　industrialflaw　detection,　security　inspection,　and　space　exploration.　However,traditional　commercial　scintillators　are　usually　associated　with　ahigh　use　cost　because　of　their　substantial　toxicity　and　easy　deliquescence.In　this　work,　an　atomically　precise　Au-Cu　cluster　scintillator(1)　with　a　thermally　activated　delayed　fluorescence　(TADF)property　was　facilely　synthesized,　which　is　environmentally　friendlyand　highly　stable　to　water　and　oxygen.　The　TADF　property　of　1　endows　it　with　an　ultrahigh　exciton　utilization　rate.　Combinedwith　the　effective　absorption　of　X-ray　caused　by　the　heavy-atom　effectand　a　limited　nonradiative　transition　caused　by　close　packing　in　thecrystal　state,　1　exhibits　an　excellent　radioluminescenceproperty.　Moreover,　1　has　good　processability　for　fabricatinga　large,　flexible　thin-film　device　(10　cm　x　10　cm)　for　high-resolutionX-ray　imaging,　which　can　reach　40　&　mu;m　(12.5　LP　mm(-1)).　The　properties　mentioned　earlier　make　the　coinage　metal　clusterpromising　for　use　as　a　substitute　for　traditional　commercial　scintillators.