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 (WS2 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/WS2 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 (Rmax) is 4.42 × 102 A/W under 365 nm UV light, the maximum specific detectivity (D*max) is 2.86 × 1011 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 WS2 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.