Broadband light detection and sensing are widely applied in modern technology. As a promising candidate for next-generation two-dimensional (2D) optoelectronic material, bismuth oxyselenide (Bi₂O₂Se) nanoplates exhibit many prospects in the application of visible light detection due to their peculiar properties. In this work, we report the photodetection performance of single-crystal 2D Bi₂O₂Se nanoplates grown on SiO₂ based on a ternary-alloy growth model by utilizing chemical vapor deposition (CVD). The Bi₂O₂Se nanoplates were found to have an even and uniform square shape with side lengths up to 15 µm and an approximate thickness of 15 nm. A visible-light photodetector was fabricated based on a CVD-grown Bi₂O₂Se nanoplate, and characterized by a set of illumination experiments using a 400 nm laser at temperatures ranging from 77 to 370 K. The device exhibited superior performance at the temperature of 77 K, with a responsivity of 523 A/W, a specific detectivity of 1.37 × 10¹¹ Jones, a response time of 0.2175 ms, and an external quantum efficiency of 162,119.44%, resulting in high-quality and full-color imaging in the visible spectrum. These results indicate that the single-crystalline Bi₂O₂Se nanoplates have excellent potential in broadband photodetection and non-cryogenic imaging.

The demand for future semiconductor devices with enhanced performance and lower cost has driven the development of epitaxial growth of high quality, free-standing semiconductor thin film materials without the requirement of lattice matching to the substrate, as well as their transfer to other substrates and associated device processing technology. This work presents a study on the van der Waals epitaxy based molecular beam epitaxy of CdSe thin films on two-dimensional layered mica substrates, as well as related etch-free layer transfer technology of large area, free-standing layers and their application in flexible photodetectors for full-color imaging. The photoconductor detectors based on these flexible CdSe thin films demonstrate excellent device performance at room temperature in terms of responsivity (0.2 A·W^–1) and detectivity (1.5 × 10¹² Jones), leading to excellent full-color imaging quality in the visible spectral range. An etch-free and damage-free layer transfer method has been developed for transferring these CdSe thin films from mica to other substrate for further device processing and integration. These results demonstrate the feasibility of van der Waals epitaxy method for growing high quality, large area, and free-standing epitaxial layers without the requirement for lattice matching to substrate for applications in low-cost flexible and/or monolithic integrated optoelectronic devices.