Quantum-Dots-Based Phase Separation into a 3D/0D Perovskite Heterojunction for Boosting X-Ray Detector Performance

Direct conversion X-ray detectors based on metal halide perovskites (MHPs), notably CsPbBr₃, promise high performance but suffer from detrimental dark currents and ion migration. Engineering stable and effective electrode interfaces remains a critical bottleneck. This work introduces a quantum dot (QD)-assisted hot-pressing strategy enabling precise control over the interfacial electric field (IEF) through tailored CsPbBr₃/Cs₄PbBr₆ heterojunctions. Synergistic QDs precursor defect engineering and controlled QD nanocrystals secondary growth during hot-pressing facilitate the formation of heterostructures with tunable phase composition at the interface. Optimized devices feature a thick (101 µm), large-grained (26 µm) orthorhombic CsPbBr₃ absorber integrated with an underlying hexagonal Cs₄PbBr₆ layer. Kelvin probe force microscopy (KPFM) directly verifies a built-in potential step (~21 mV) at the interface, establishing an IEF that cooperates with the Type-II band alignment to effectively suppress dark current injection, restrict ion migration, and promote efficient charge separation. Consequently, the engineered detectors demonstrate an outstandingly low dark current density (0.1 nA cm⁻² at 1 V/mm). The device exhibits dramatically improved carrier transport with an 8-fold enhancement in carrier lifetime (from 1.6 s to 12 s), and clinches a high X-ray sensitivity of 12910 μC Gyair⁻¹ cm⁻² (at 85 V/mm), yet still maintaining the ultra-low dark current baseline. When integrated with a 256 × 256 pixel TFT board, a large area X-ray imaging detector was created, which delivered high resolution and high contrast images for various fine industrial products.