Transparent and Planar Cs₃Cu₂Cl₅ Crystals for Micrometer-Resolution X-ray Imaging Screen

Copper-based (I) halide perovskites have emerged as a promising candidate for scintillation screens in X-ray inspection and imaging areas due to their solution processability and high light yield. Here, a centimeter-sized Cs₃Cu₂Cl₅ single crystal was grown by a slow-cooling method. The planar orientation was controlled in a space-confined chamber, generating a planar crystal which is readily used for a scintillation screen without any further shaping. The crystal exhibited a unity photoluminescence quantum yield and superior scintillation performance. The Cs₃Cu₂Cl₅ single crystal exhibited a high light yield up to 95,000 photons/MeV, which enabled an X-ray detector of a detection limit down to 2.7 μGy_air/s. The homemade imager demonstrated a spatial resolution of 105 lp/mm, representing an unprecedented micrometer resolution in laboratory. Importantly, the stability of Cs₃Cu₂Cl₅ was significantly improved by a new surface passivation procedure, whereby the passivated crystal reserved its phase after 6 months' storage in a vial. This work introduced a new solution-based synthetic method for two-dimensional scintillating crystals, opening many avenues to high-performance X-ray imaging applications.