Thin films of chitosan with the addition of silver iodide for flexible photodetectors

Chitosan composite thin films modified with silver iodide (AgI) are a promising material for optoelectronics. The study of their current-voltage characteristics in the range of 0–15 V showed that in the dark, the samples have a high intrinsic resistance (leakage current ≤5 nA at 15 V), demonstrating ohmic behavior. Under the influence of optical radiation (100 mW/cm²), a linear increase in conductivity is observed: the photocurrent reaches 65 nA at 15 V with a slope of ⁓4 nA/V. The photoconductivity of the material is due to the absorption of light in the range of 400–420 nm (violet light) and 520–540 nm (green light), which leads to the generation of charge carriers and a resistance decrease. The chitosan matrix provides stabilization of AgI nanoparticles and flexibility of the composite. The photoresistors demonstrate a good response to solar radiation. The highest photosensitivity is observed under sunlight illumination due to its wide spectral range.