Nanostructured Copper Iodide Film in a Multifunctional Flexible Device for Ultraviolet Photodetection and Ammonia Monitoring

A flexible, lightweight, and portable device integrating the functions of an ammonia gas sensor and an ultraviolet (UV) photodetector operating at room temperature is developed using available materials with no physiological toxicity and low manufacturing cost by employing the low-temperature aqueous successive ionic layer adsorption and reaction (SILAR) method to deposit a nanostructured copper iodide (CuI) thin film on a flexible polyethylene (PE) substrate. Under the irradiation of UV radiation, it functions as a flexible photoconductive UV photodetector with a photoconductivity gain of 1.17, a sensitivity of 2.3 mA/W, a specific detectivity of 1 × 109 Jones and an external quantum efficiency of 0.8% with a response/recovery time of several minutes. It is quite suitable for wearable personal UV monitoring devices and as an electronic eye in door security system. The high selective sensitivity of the device to ammonia (NH3) is due to the synergistic effect of the electron donor gas NH3 on the p-type semiconductor CuI and its ability to complexing NH3. The detection limit of 0.15 ppm of the CuI/PE chemiresistive ammonia sensor and its fast response/recovery make it suitable for food spoilage detection, real-time monitoring of ammonia leaks, and in medical diagnosis by detecting NH3 in exhaled air.