Ligand‐Engineered All‐In‐One Cu(I) Iodide Complex Enables Near‐Unity Photoluminescence and Advanced 3D X‐ray Image Reconstruction

Abstract High‐performance X‐ray detectors are essential for 3D X‐ray imaging in computed tomography (CT), but conventional systems require high radiation doses to achieve fine resolution. All‐In‐One (AIO) Cu(I) halide complexes, capable of forming both ionic and coordinate bonds within a single structure, offer efficient scintillation at lower doses, yet their performance remains limited by nonradiative energy losses during indirect X‐ray‐to‐light conversion. Here, we develop rigid‐cation‐assisted AIO Cu(I) halide complexes by introducing π–π interactions to suppress the nonradiative pathways, achieving near‐unity photoluminescence quantum yield (PLQY). In particular, the rigid (benzyl‐DABCO) 2 Cu 5 I 7 (Bz‐Cu 5 I 7 ) complex stabilizes triplet emissive states, thereby facilitating high‐efficiency radiative recombination and excellent radioluminescence (RL) properties. When incorporated into flexible scintillator film, Bz‐Cu 5 I 7 demonstrates remarkable X‐ray imaging performance, enabling a high spatial resolution exceeding 20 lp mm −1 and a low radiation dose of 71.2 nGy air s −1 . Importantly, 3D X‐ray image reconstruction of small electronic components reveals fine structural details, highlighting the potential of Bz‐Cu 5 I 7 as a next‐generation X‐ray scintillator for low‐dose CT imaging.