High-Performance Dual-Mode UV Photodetection from a Single Maneuverable X-Shaped Cs₃Cu₂I₅ Microcrystal

Ultraviolet photodetectors (UV PDs) based on microcrystals (MCs) have attracted extensive attention due to their outstanding detection performance. Nevertheless, precise manipulation of the MCs still remains challenging, which may hinder the mass processing and performance improvement of the UV PDs. In this work, a single high-quality Cs₃Cu₂I₅ MC that had a special X-shaped morphology was demonstrated to be successfully manipulated to prepare high-performance UV PDs by virtue of optical focusing, probe micromanipulation, and direct-write photolithography techniques. The UV PDs, prepared on the counter limbs and adjacent limbs of the single X-shaped Cs₃Cu₂I₅ MC, exhibited distinctly different dual-mode photoresponse under 254 nm UVC and 310 nm UVB irradiations. At light intensity as low as 2.59 μW/cm², the counter electrode and adjacent electrode UV PDs showed quite a high responsivity of up to 3376 A/W, a specific detectivity of up to 2.37 × 10¹⁴ Jones, and an on/off ratio of up to 1.79 × 10² at a bias voltage of 5 V. Besides, even after 28,800 s (8 h) of continuous operation under dual-mode UV irradiations at 254 and 310 nm, the unpackaged device showed extraordinary stability in the photocurrents in ambient air. Our findings provide inspiration for preparing high-performance dual-mode UV PDs based on the microscale perovskite-inspired copper halides or other semiconductor MCs.