Dual-Site Coordination Regulated Crystallization for High-Performance MAPbBr ₃ X-ray Detection

Organic-inorganic hybrid perovskite single crystals have shown great potential as next-generation high-sensitivity X-ray detectors. However, the thermodynamic instability of their precursor solutions often leads to disordered nucleation and defect proliferation during crystallization, which considerably limits the performance of resulting devices. This study shows that polymeric inhibitor effectively suppresses disordered nucleation in perovskite precursor solutions. The coordination mechanism between PVP and the MAPbBr₃ precursor solutions is revealed by IGMH (Independent Gradient Model based on Hirshfeld partition) analysis, density functional theory (DFT) calculations, and experimental results. It is revealed that PVP forms a distinct dual-site coordination complex with Pb²⁺, interacting simultaneously through its carbonyl and pyrrolidone ring. This specific coordination geometry significantly enhances the thermodynamic stability of the precursor system by maintaining an optimal solute concentration within the metastable zone, thus effectively inhibiting spontaneous nucleation. The MAPbBr₃ (with PVP) SC (single crystal) exhibits a low defect density of 6.56 × 10⁸ cm^-3 and a high carrier mobility-lifetime product (μτ) of 1.11 × 10^-3 cm²·V^-1. The X-ray detector fabricated based on the crystal demonstrates a high sensitivity of 1.73 × 10⁴ μC·Gy_air^-1·cm^-2 and a low detection limit of 43.55 nGy_air·s^-1. This study provides a new strategy for modulating perovskite crystallization kinetics through coordination engineering, offering a viable pathway for developing high-performance radiation detectors.