Highly Luminescent Zero-Dimensional Organic Copper Halides for X-ray Scintillation

The present work reports highly efficient flexible and reabsorption-free scintillators based on two zero-dimensional (0D) organic copper halides (TBA)CuX₂ (TBA = tetrabutylammonium cation; X = Cl, Br). The (TBA)CuX₂ exhibit highly luminescent green and sky-blue emissions peaked at 510 and 498 nm, with large Stokes shifts of 224 and 209 nm and high photoluminescence quantum yields (PLQYs) of 92.8% and 80.5% at room temperature for (TBA)CuCl₂ and (TBA)CuBr₂ single crystals (SCs), respectively. Interestingly, above room temperature, their PLQYs increase with temperature and reach near unity at 320 and 345 K for (TBA)CuCl₂ and (TBA)CuBr₂, respectively. The excellent properties originate from self-trapped excitons (STEs) in individual [CuX₂]^- quantum rods, which is demonstrated by the temperature-dependent PL, ultrafast transient absorption (TA) combined with density functional theory (DFT) calculations. The (TBA)CuX₂ scintillators show bright radioluminescence (RL), impressive linear response to dose rate in a broad range, and high light yields. Their potential application in X-ray imaging is demonstrated by using (TBA)CuX₂ composite scintillation screens. Importantly, flexible scintillators are demonstrated to be superior than flat ones for imaging nonplanar objects by conformally coating, which produce accurate images with negligible distortion.