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

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)₂Cu₅I₇ (Bz-Cu₅I₇) complex stabilizes triplet emissive states, thereby facilitating high-efficiency radiative recombination and excellent radioluminescence (RL) properties. When incorporated into flexible scintillator film, Bz-Cu₅I₇ 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-Cu₅I₇ as a next-generation X-ray scintillator for low-dose CT imaging.