Kinetically regulated growth of Cs3Cu2I5 single-crystalline thin films for highly responsive and stable deep-ultraviolet photodetectors

The newly emerging copper halide Cs3Cu2I5 is a promising candidate for deep-ultraviolet photodetector applications. However, the device performance available today is plagued by massive grain boundaries in Cs3Cu2I5 polycrystalline films and unnecessary thicker volume in bulk single crystals. In this study, for the first time, highly crystalline and stable Cs3Cu2I5 single-crystalline thin films (SCFs) were prepared by facile supersaturation-controlled growth strategy, with adjustable thickness ranging from 45 nm to 27.9 µm. By in situ monitoring the growth process, the crystallization kinetics of Cs3Cu2I5 SCFs were elucidated, and the crystallization driving force comes from the slow inverse temperature nucleation and evaporation crystallization. Moreover, the substrate-independent growth feature of Cs3Cu2I5 SCFs is intriguing for the direct on-chip fabrication of diverse photoelectric devices. The structural and electric characterizations reveal that the Cs3Cu2I5 SCFs have a low trap density of 6.42 × 1011 cm−3, and the measured carrier lifetime and diffusion length are as long as 1.32 μs and 1.85 µm, respectively, which enable high deep-ultraviolet light detection capability of the proposed photoconductive detector based on Cs3Cu2I5 SCFs. Encouraged by the robust operating stability of the fabricated device, the above results obtained could catalyze further research on on-chip manufacturing of deep-ultraviolet photodetectors.