Nucleation Engineering in Sprayed MA₃Bi₂I₉ Films for Direct-Conversion X-ray Detectors

Area of Science:

• Materials Science
• Solid-State Physics
• Detector Technology

Background:

• Metal halide perovskites show potential for X-ray detection applications.
• Fabricating high-quality, thick perovskite films for large-scale use is challenging due to defects like cracks and pinholes during crystallization.

Purpose of the Study:

• To develop a scalable and cost-effective method for fabricating high-quality perovskite films for X-ray detection.
• To investigate the effect of MACl additive on the crystallization process and film properties of MA₃Bi₂I₉.

Main Methods:

• Fabrication of MA₃Bi₂I₉ films using a cost-effective, scalable spraying process.
• Utilized MACl as an additive to control the crystallization process.
• Characterized the film's microstructure, carrier mobility, and activation energy for ion migration.
• Fabricated and tested X-ray detectors with an ITO/MA₃Bi₂I₉/Au configuration.

Main Results:

• Achieved a dense MA₃Bi₂I₉ film composed of large grains.
• The film exhibited high carrier mobility (∼1 cm² V^-1 s^-1) and a significant activation energy for ion migration (0.91 eV).
• The fabricated X-ray detectors demonstrated a sensitivity of 35 μC Gy_air^-1 cm^-2 and a limit of detection of 0.14 μGy_airs^-1.

Conclusions:

• The spraying process with MACl additive is an effective strategy for producing high-quality MA₃Bi₂I₉ perovskite films.
• The developed perovskite films possess excellent optoelectronic properties suitable for advanced X-ray detection.
• The performance of the MA₃Bi₂I₉ detectors surpasses that of commercial α-Se detectors, indicating significant potential for practical applications.