Double‐Sided Bifunctional Blue‐Green Light Photodetector Based on Liquid Crystalline Polymer for Light Positioning and Health Monitoring

Abstract Wearable blue‐green photodetectors have attracted considerable attention in underwater and medical applications. However, semiconductor‐based photodetectors generally suffer from inevitable performance deterioration because of elastic modulus mismatch between rigid inorganic materials and polymer matrixes. Besides, most of the photodetectors reported so far can't be used on both sides and the multiple functionalizations can only be realized by stacking different types of devices. Herein, an intrinsically flexible and size‐customizable blue‐green photodetector has been fabricated based on well‐designed composite fabrics with oriented electrospun fibers, consisting of pseudo‐stilbene azobenzene‐containing cross–linked liquid crystalline polymers (NAzo‐CLCP) and piezoelectric poly(vinylidene fluoride‐trifluoroethylene) [P(VDF‐TrFE)] nanogenerator. Taking advantage of the synergistic effect between liquid crystalline alignment and polymer networks, the NAzo‐CLCP devices construct a consecutive and efficient conversion of illuminance – internal stress – electric signal. A responsivity of 233 mV W −1 is achieved in voltage signals and a comparable response time of 0.1 s in current signals compared to the reported wearable semiconductor‐based photodetectors. Benefiting from the inherent flexibility and compatibility of the hydrophobic fabrics, the NAzo‐CLCP devices exhibit robust stabilities under cyclic irradiations, humidity and temperature variations, and especially slightly dynamic conditions, fulfilling basic requirements for wearable electronics. For practical applications, a photodetector array for light positioning based on blue light and a bracelet for real‐time health monitoring based on green light are developed. Profiting from the uniformity of the fabrics and the consistency of detection performance, the integrated bifunction of code transmission and health monitoring over a double‐sided one‐piece photodetector has been realized for the first time, providing extensive potential for wearable electronics based on the NAzo‐CLCP fabrics.