Improved functionality of PEDOT:PSS thin films via graphene doping, fabricated by ultrasonic substrate vibration-assisted spray coating

- Graphene-PEDOT:PSS composite thin films were fabricated by ultrasonic substrate vibration-assisted spray coating.
- The electrical conductivity of graphene-PEDOT:PSS composite film reached 720 S/m, 10-fold enhanced comparing to the pristine PEDOT:PSS.
- Graphene sheets bridge between the PEDOT:PSS rings via the strong π-π interaction acting as high-mobility channel.
- Substrate vibration promotes the film homogeneity and lead to an enhancement in film transparency.
- A mild drying temperature of 80 °C is favored, leading to better structural arrangement of graphene bridging between the polymer segments.

The composite thin film of graphene and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) is a promising candidate of hole transport layer and transparent conductive electrode materials for low-cost thin film devices. We use novel, fast, controllable and scalable ultrasonic substrate vibration-assisted spray coating (SVASC) method to fabricate high-performance graphene-PEDOT:PSS composite thin films. Graphene sheets are uniformly dispersed in aqueous PEDOT:PSS solution using sodium dodecyl sulfonate as surfactant. The fabricated graphene-PEDOT:PSS composite thin films exhibit excellent electrical and optical properties. The electrical conductivity of composite PEDOT:PSS thin films reaches 720 S/cm, which is increased about 10 times when 0.02 wt% of graphene is incorporated in the precursor solution. This remarkable enhancement is ascribed to the higher carrier mobility and carrier concentration, because graphene sheets bridge between the PEDOT:PSS rings via the strong π-π interaction acting as high-mobility channel. Also, the π-π interaction causes a reduction in the defect sites in PEDOT:PSS. Moreover, a mild drying temperature of 80 °C is favored, leading to better structural arrangement of graphene bridging between the polymer segments, and higher electrical conductivity. This work simplifies the solution-processing of graphene and uses a scalable casting technique, which paves the way for the commercialization of low-cost flexible electronic devices.