The search for color-tunable, efficient, and robust scintillators plays a vital role in the development of modern X-ray radiography. The radioluminescence tuning of copper iodide cluster scintillators in the entire visible region by bandgap engineering is herein reported. The bandgap engineering benefits from the fact that the conduction band minimum and valence band maximum of copper iodide cluster crystals are contributed by atomic orbitals from the inorganic core and organic ligand components, respectively. In addition to high scintillation performance, the as-prepared crystalline copper iodide cluster solids exhibit remarkable resistance toward both moisture and X-ray irradiation. These features allow copper iodide cluster scintillators to show particular attractiveness for low-dose X-ray radiography with a detection limit of 55 nGy s
