Recrystallization of single crystal CsCu2I3 perovskites by I2 treatment for enhanced UV detecting abilities†

Abstract

Single crystal copper halide perovskites (CsCu₂I₃) have gained extensive interest due to their nontoxic composition and superior ultraviolet (UV) photodetecting abilities. However, the surface defects of single crystal CsCu₂I₃, especially iodine (I) defects, limit its further improvement of photodetecting performance. Here, single crystal CsCu₂I₃ halides with a length of 1.6 cm are initially prepared by an anti-solvent vapor-assisted approach. The recrystallization and reduction of I vacancies of single crystal materials were realized by annealing them under an I₂ vapor atmosphere, displaying a clear (ll0) orientation. Compared with original CsCu₂I₃, the on/off ratio of I₂ treated CsCu₂I₃ is enhanced 9.1 times with a value increased from 181 to 1655. Specifically, an I₂ treated UV photodetector exhibits narrowband responsivity with a FWHM of ∼50 nm, high detectivity (3.1 × 10¹¹ Jones), and fast response speed (rise time: 0.11 ms and decay time: 1.89 ms) at 370 nm (light intensity: 2.8 mW cm⁻²). The approach of treating I-based perovskites under an I₂ atmosphere may have great application prospects in the field of optoelectronics.