Fabrication of Bi19S27I3 nanorod cluster films for enhanced photodetection performance.

Thin-film photodetectors built from one-dimensional nanostructures have attracted extensive attention due to their significance in basic scientific research and potential technological applications. It is still desirable to develop new materials with a wide response range for application in photodetectors. In this work, a Bi19S27I3 nanorod cluster film has been successfully fabricated on various rigid substrates by a facile solvothermal method. The component nanorods exhibit an oriented growth along the [001] direction. The UV-Vis-NIR absorption spectrum shows a continuous strong absorption spanning the whole visible light to near-infrared region and presents a direct band gap of 0.83 eV for the prepared Bi19S27I3 nanorod clusters. The spectral photoresponse of the Bi19S27I3-based photodetector device demonstrates a broad photoresponse ranging from ultraviolet to near infrared. The photocurrent results reveal that the photodetector exhibits a more sensitive response towards near-infrared light than visible light. Furthermore, the photodetector based on the Bi19S27I3 nanorod cluster film shows significantly enhanced photodetection performance compared to Bi19S27I3 nanorod powder. The photocurrent and on-off ratio of the prepared nanorod cluster film are respectively up to 400 times and several times higher than those of the powder sample. The on-off ratios are about 265 and 66 under NIR illumination and 48 and 11 under visible light for the film and powder samples, respectively. These results suggest a great potential application of the prepared Bi19S27I3 nanorod cluster film in optoelectronic devices.