Highly Sensitive and Stable Visible-Light Self-Power Photodetectors Based on Solution-Processed Bi₄O₅I₂

Bismuth oxyiodides have been gradually regarded as a kind of promising optoelectronic material, owing to their various merits, like relatively narrow and tunable band gap, high anisotropic crystal structure, and less toxicity. However, the investigation of bismuth oxyiodide-based photodetectors is still in the early stage, which might be attributed to the immature film deposition techniques in controlling their phase composition and surface morphology. In this work, high-quality Bi 4 O 5 I 2 thin films were synthesized for the first time by a facile solution-based deposition technique, mist chemical vapor deposition. The synthesized Bi 4 O 5 I 2 thin films were composed of vertically aligned nanoplatelets. With the increasing synthesis temperatures, the size of the nanoplates and film thickness increased. The iodide content was influenced by the synthesis temperatures such that the I:Bi molar ratio for the Bi 4 O 5 I 2 thin films at intermediate temperature was close to 50%. The Bi 4 O 5 I 2 photoelectrochemical (PEC)-type photodetectors were fabricated and exhibited excellent photodetection performance with the highest responsivity of 19.4 mA/W and detectivity of 3.54 × 10 10 Jones. In addition, Bi 4 O 5 I 2 PEC-type photodetectors presented good long-term stability in that the photocurrent density only decreased by around 25% after 6 h, which was superior to most 2D material-based PEC-type photodetectors. These results demonstrated that the Bi 4 O 5 I 2 thin film has great potential in high-performance optoelectronic devices.