Yellow Emissive CsCu 2 I 3 Nanocrystals Induced by Mn 2+ 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 CsCu 2 I 3 nanocrystals (NCs) were successfully prepared via a simple Mn 2+ -assisted hot-injection method. The added Mn 2+ effectively induced the phase transformation from Cs 3 Cu 2 I 5 to CsCu 2 I 3 , leading to the preparation of single-phase CsCu 2 I 3 NCs with few defects and a high fluorescence performance. The as-prepared "optimal CsCu 2 I 3 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 CsCu 2 I 3 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 CsCu 2 I 3 NCs scintillator film achieved an ultrahigh (16.6 lp mm -1 ) spatial resolution in X-ray imaging. The CsCu 2 I 3 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.