From BiI3 to CuBiI4: a striking improvement in the photoelectric performance of a novel photodetector candidate.

Bismuth halide based semiconductors have attracted increasing attention as the next generation photodetectors because of their excellent photoelectric performance, environmental friendliness, and high-element-abundance characteristics. However, it is still challenging to prepare a thin film under normal conditions because of the instability of BiI₃. In this work, we use a room temperature elemental powder reaction in ambient conditions for the easy preparation of Cu incorporated perovskite-like CuBiI₄ on a large scale. The crystalline and photoelectric characteristics of the resulting CuBiI₄ thin films with different initial Cu content have been investigated by X-ray diffraction (XRD), UV-Vis spectroscopy, photoluminescence spectroscopy (PL), and transient surface photovoltage (TSPV) studies. The CuBiI₄ based photodetectors were first assembled, which showed a striking improvement in the responsivity of the photodetectors compared with pure binary BiI₃. Particularly, the responsivity of the photodetector with a 1 : 1 molar ratio of copper to bismuth is 10⁶ times larger than that with an initial molar ratio of 0 : 1 (pure BiI₃). A possible mechanism for such an improvement was preliminarily discussed by taking advantage of the Hall effect measurements. Our work not only provides a universal synthetic strategy for preparing high quality Bi-based perovskite-like photoelectric materials but also presents a novel Bi-based photodetector material. [ABSTRACT FROM AUTHOR]