Hydrogel flexible photodetector based on polarization of free water molecules and image sensor application

Abstract

Flexible photodetectors are promising for a wide range of applications, including wearable devices, medical equipment, smart homes, energy harvesting, and storage. However, conventional manufacturing methods often face challenges such as complexity, high costs, and poor stability. In this study, we present a flexible photodetector based on a hydrogel design, achieving a responsivity of 4.32 mA/W and a detectivity of 9.09 × 10⁹ Jones at 360 nm under zero bias, with rapid response times characterized by a rise time of 45.6 ms and a fall time of 34.5 ms. The core working principle of the Gr-PEDOT/Alg(Fe³⁺)-TiO₂ photodetector relies on the photo-polarization of water molecules in the hydrogel, which is driven by the built-in electric field formed at the interface between semiconductors with different Fermi levels under illumination, enabling self-powered UV detection. The device features excellent mechanical stretchability and high optical transparency, making it well-suited for applications such as wearable electronics, portable cameras, and transparent or semi-transparent devices. To explore its potential further, we fabricate an 8 × 8 flexible photodetector array capable of capturing images under bending conditions and detecting incident light signals from multiple angles. By integrating the images captured by the 8 × 8 flexible photodetector array with convolutional neural networks (CNNs), the system achieves precise image recognition even under bending conditions, demonstrating promising applications in artificial intelligence and machine learning. This work highlights the significant advantages of flexible Gr-PEDOT/Alg(Fe³⁺)-TiO₂ photodetectors and provides valuable insights into their application in optoelectronic imaging and artificial intelligence technologies.