Highly Reactive Crystalline (001) Facet of BiI₃ Hexagonal Nanoplates for Visible Light Photodetectors

A simple and facile solution phase synthesis of large-scale, micro-to-nanometer sized bismuth triiodide (BiI 3 ) single crystalline hexagonal plates is reported. It is demonstrated that under optimized conditions the reactions result in dominant exposed (001) facets. Because of the large size, high surface-to-volume ratio, and thickness, BiI 3 nanoplatelets are attractive as visible light photodetectors. At 1 V bias, the photoresponsivity is 0.87 A W –1; the specific detectivity is 4.8 × 10 12 jones with a response rise time of 1 s and a fall time of 0.97 s. The Kelvin probe force microscope images revealed that the surface potential difference across the junction was 42.5 mV, which is attributed to the work function difference between the sample and substrate. The results of this study indicate that single hexagonal platelets of BiI 3 are very promising for visible light photodetector applications.