Photoelectrochemical BiSI-based visible light detector

We suggest a photoelectrochemical detector based on semiconductor bismuth thioiodide BiSI with the band gap energy Eg = 1.59 eV (direct optical transitions). The bismuth thioiodide was synthesized by the chemical bath deposition on a conductive FTO glass. The structure of BiSI film represents randomly oriented needle-like single crystals. The nucleation and growth of needle-like BiSI single crystals from a single center and the absence of inter-crystallite boundaries provide a high external quantum efficiency of photocurrent up to 52 % at 400 nm. It corresponds to ampere-watt responsivity of 0.16 A/W. BiSI photodetector possesses a high specific detectivity of 3.4•1011 cm•Hz1/2/W and an on/off time equal to 26/435 ms. In aqueous electrolyte containing both S2− and I− anions, the photodetector is characterized by a high temporal stability of photocurrent and cyclability (thousands of cycles) under visible light illumination.