Fully Flexible Yarn-Based Phototransistors for UV–Visible Light Detection

A novel flexible photodetector using yarn-based phototransistors is reported for the first-time. Reduced graphene oxide (rGO) doped with poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) was prepared by simple solution processing and coated by tungsten disulfide quantum dots (WS 2 QDs) for novel yarn-based phototransistors (YPTs). The transistor-based photodetector exhibits good p-type transistor behavior and high transconductance (4.7 mS). The YPTs with an rGO-PEDOT:PSS/WS 2 QDs heterojunction as the photosensitive layer are regulated by different light wavelength, light power, and gate voltage with UV–visible light. It is observed that the highest photoresponsivity of the device ( R max ) is 4.42 × 10 2 A/W under 365 nm UV light, the maximum specific detectivity ( D * max ) is 2.86 × 10 11 Jones, and the fast response and recovery times are 1.78 and 2.91 s under a broad wavelength range, respectively. This excellent performance can be attributed to the synergistic effect of the WS 2 QDs/rGO-PEDOT:PSS composites. In addition, the fully flexible phototransistor prepared by composite nanomaterials coated on viscose yarn still maintains a stable performance under different bending states and has been successfully applied in the field of UV–visible visual detection and intelligent wearable optoelectronics. These results pave a simple route for the development of wearable, high-performance optoelectronic devices.