Impurity PbCO₃ from Low-Purity Raw Material Improves MAPbBr₃ Single-Crystalline X-ray Detectors

Perovskite single crystals have been found to exhibit excellent X-ray detection and imaging performance. High-purity raw materials have generally been considered a prerequisite to guarantee crystal quality and device performance, which may lead to higher costs. However, we found that higher quality MAPbBr₃ single crystals can be obtained from low-purity lead bromide (PbBr₂). This is attributed to the presence of impurity lead carbonate (PbCO₃) in the raw material. PbCO₃ facilitates the suppression of crystal defects, leading to higher quality crystals. With the addition of a small amount of PbCO₃ to high-purity PbBr₂ raw material, MAPbBr₃ single crystals grow with a smoother surface, improved uniformity, and lower defect concentrations. The single crystal becomes more intrinsic. The product of carrier mobility and lifetime increases to 1.3 × 10^-2 cm² V^-1. With the addition of PbCO₃, the detector sensitivity is about twice as high and the lowest detection limit is approximately 300 times lower, down to 20 nGy_air/s. This work reveals the key factors for preparing high-quality perovskite single crystals using low-cost, low-purity raw materials, providing a new approach for producing high-yield perovskite single crystals.