Yellow Emissive CsCu₂I₃ Nanocrystals Induced by Mn²⁺ for High-Resolution X-ray Imaging

Recently, low-dimensional copper(I)-based perovskite or derivatives have gained extensive attention in scintillator applications because of their environmental friendliness and good stabilities. However, the unsatisfactory scintillation performance and complex fabrication processes hindered their practical applications. Herein, efficient yellow emissive CsCu₂I₃ nanocrystals (NCs) were successfully prepared via a simple Mn²⁺-assisted hot-injection method. The added Mn²⁺ effectively induced the phase transformation from Cs₃Cu₂I₅ to CsCu₂I₃, leading to the preparation of single-phase CsCu₂I₃ NCs with few defects and a high fluorescence performance. The as-prepared "optimal CsCu₂I₃ NCs" exhibited superior photoluminescence (PL) performance with a record-high PL quantum yield (PLQY) of 61.9%. The excellent fluorescence originated from the radiative recombination of strongly localized one-dimension (1D) self-trapped excitons (STEs), which was systematically investigated via the wavelength-dependent PL excitation, PL emission, and temperature-dependent PL spectra. These CsCu₂I₃ NCs also exhibited outstanding X-ray scintillation properties with a high light yield (32000 photons MeV^-1) and an ultralow detection limit (80.2 nGy_air s^-1). Eventually, the CsCu₂I₃ NCs scintillator film achieved an ultrahigh (16.6 lp mm^-1) spatial resolution in X-ray imaging. The CsCu₂I₃ NCs also exhibited good stabilities against X-ray irradiation, heat, and environmental storage, indicating their great application potential in flexible X-ray detection and imaging.