Quantum-dots-based phase separation into a 3D/0D perovskite heterojunction for boosting X-ray detector performance

Area of Science:

• Materials Science
• Solid-State Physics
• Medical Imaging Technology

Background:

• Direct conversion X-ray detectors using metal halide perovskites (MHPs) offer high performance potential.
• However, challenges like dark currents and ion migration hinder their practical application, primarily due to difficulties in engineering stable electrode interfaces.

Purpose of the Study:

• To develop a novel strategy for enhancing the stability and performance of MHP-based X-ray detectors.
• To precisely control the interfacial electric field (IEF) and suppress detrimental charge carrier behaviors.

Main Methods:

• A quantum dot (QD)-assisted hot-pressing technique was employed to fabricate CsPbBr₃/Cs₄PbBr₆ heterojunctions.
• Synergistic defect engineering of precursor QDs and controlled secondary growth during hot-pressing were utilized to tune interfacial properties.
• Kelvin probe force microscopy (KPFM) was used to characterize the interfacial electric field (IEF).

Main Results:

• Optimized devices exhibited a CsPbBr₃/Cs₄PbBr₆ heterostructure with a verified built-in potential step (∼21 mV) at the interface.
• The engineered IEF, combined with Type-II band alignment, effectively suppressed dark current injection and ion migration.
• Achieved an ultra-low dark current density (0.1 nA cm^-2 at 1 V mm^-1), an 8-fold increase in carrier lifetime (1.6 ns to 12 ns), and high X-ray sensitivity (12,910 μC Gy_air^-1 cm^-2).

Conclusions:

• The QD-assisted hot-pressing strategy provides precise control over interfacial properties in MHP detectors.
• This method successfully overcomes key limitations of dark current and ion migration, leading to significantly enhanced detector performance.
• Demonstrated potential for large-area, high-resolution X-ray imaging applications through integration with TFT technology.