Zero-dimensional rubidium zinc halide blue-emitting quantum dots for X-ray imaging

Low-dimensional-networked metal halide (MH) materials are emerged as a new class of semiconductors owing to their unique structure and outstanding photoelectric properties. Compared with the extensively studied three-dimensional (3D) MHs, the zero-dimensional (0D) MHs are of great interest to be widely studied. Here we report the successful colloidal synthesis of all-inorganic lead-free 0D MHs, including undoped and Cu-doped Rb2ZnCl4 quantum dots (QDs) with bright broad blue and cyan emissions, respectively. Combining the theoretical and experimental study, the band structures are well characterized and the originations of the blue and cyan emissions are attributed to the singlet and triplet self-trapped exciton (STE) emissions, respectively. Finally, owing to the bright radioluminescence (RL), the Cu-doped Rb2ZnCl4 QDs is prepared into a thin film to demonstrate the feasibility for X-ray imaging application. This work not only provides a cyan-emitting all-inorganic 0D MH QDs, but also exploits it as a scintillator for X-ray imaging.