PF6− Pseudohalides Anion Based Metal‐Free Perovskite Single Crystal for Stable X‐Ray Detector to Attain Record Sensitivity

• Published in: Advanced materials (Weinheim) Vol. 35; no. 25; pp. e2300480 - n/a
• Main Authors: Li, Zhizai, Li, ZhenHua, Peng, Guoqiang, Shi, Chang, Wang, Haoxu, Ding, San‐Yuan, Wang, Qian, Liu, Zitong, Jin, Zhiwen
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.06.2023
• Subjects: Bonding strength; coulomb interaction; Detectors; Dosage; Electronegativity; Energy bands; hydrogen bond; Hydrogen bonding; Iodine; Ion migration; Low currents; Materials science; metal‐free perovskite; Oxidation; Perovskites; PF6− pseudohalides; Physical properties; Sensitivity; Single crystals; Stability; x‐ray detection
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202300480

Metal‐free perovskites (MFPs) possess excellent photophysical properties of perovskites while avoiding the introduction of toxic metal ions and organic solvents, and have been expanded to X‐ray detection. However, iodine‐based high‐performance MFPs are tended to oxidation, corrosion, and uncontrolled ion migration, resulting in poor material stability and device performance. Herein, the strongly electronegative PF6− pseudohalide is used to fabricate the large‐size MDABCO‐NH4(PF6)3 (MDBACO = methyl‐N′‐diazabicyclo[2.2.2]octonium) single crystals (SCs) for solving the problems of iodine ions. After the introduction of PF6− pseudohalides, the Coulomb interaction and hydrogen bonding strength are enhanced to alleviate the ion‐migration and stability problems. Moreover, combined with theoretical calculations, PF6− pseudohalides increase the ion‐migration barrier, and affect the contribution of its components to the energy band for a broadening bandgap. Meanwhile, the improved physical properties, such as large activation energy of ionic migration, high resistivity, and low current drift, further expand its application in low‐dose and sensitive X‐ray detection. Finally, the X‐ray detector based on MDABCO‐NH4(PF6)3 SCs achieves a sensitivity of 2078 µC Gyair−1 cm−2 (highest among metal‐free SCs‐based detectors) and the lowest detectable dose rate (16.3 nGyair s−1). This work has expanded the selection of MFPs for X‐ray detectors and somewhat advanced the development of high‐performance devices. This work novelly introduces strong electronegative PF6− pseudohalides and synthesizes the metal‐free MDABCO‐NH4(PF6)3 perovskites to solve the problems of oxidation, corrosion, and uncontrolled ion migration in common I‐based MFPs. Importantly, the advanced SC‐based X‐ray detector achieves the highest sensitivity of 2078 µC Gyair−1 cm‐2, an ultra‐low LoD of 16.3 nGyair s−1, and superior environmental and operational stability for practical applications.