Sunscreen-Inspired ZnO/PEG Composites for Flexible Ultraviolet Photodetectors with a Giant On–Off Ratio

Zinc oxide (ZnO) nanomaterials have attracted much attention in UV photodetectors owing to the suitable band gap and high photoelectric conversion efficiency. However, the loose structure of nanomaterials assembled by a low-temperature process cannot meet the mechanical requirements of flexible photodetectors. The high dark current caused by defects in ZnO severely drags down the response performance of photodetectors. To address these issues, we have proposed a novel strategy for constructing flexible photodetectors based on ZnO and poly(ethylene glycol) (PEG) composites. Inspired by the sunscreen, the addition of PEG can enhance the interaction of ZnO nanoparticles, thus improving the film-forming ability and the mechanical endurance of the composites. By coating the ZnO/PEG composite on a common printing paper, the flexible photodetector shows unexpected good performance, such as a high responsivity of 1.77 A·W–1 and a large specific detectivity of 3.89 × 1013 Jones. Notably, a giant on–off ratio of up to 1.99 × 105 has been achieved by suppression of dark current. The device also exhibits satisfactory mechanical flexibility after long-term bending tests. In addition, the low-cost raw materials and scalable manufacturing processes further expand its application prospects in flexible optoelectronic technologies.