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 (R-max) is 4.42 x 10(2) A/W under 365 nm UV light, the maximum specific detectivity (D*(max)) is 2.86 x 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 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.