Effect of HDI-Modified GO on the Thermoelectric Performance of Poly(3,4-ethylenedioxythiophene):Poly(Styrenesulfonate) Nanocomposite Films

Abstract

Composite films based on conducting polymers and carbon nanomaterials have attracted much attention for applications in various devices, such as chemical sensors, light-emitting diodes (LEDs), organic solar cells (OSCs), among others. Graphene oxide (GO) is an ideal filler for polymeric matrices due to its unique properties. However, GO needs to be functionalized to improve its solubility in common solvents and enable the processing by low-cost solution deposition methods. In this work, hexamethylene diisocyanate (HDI)-modified GO and its nanocomposites with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) were developed, and their morphology, thermal, electrical, thermoelectrical and mechanical performance were characterized. The influence of the HDI functionalization degree and concentration on the nanocomposite properties were assessed. The HDI-GO increased the crystallinity, lamella stacking and interchain coupling of PEDOT:PSS chains. A strong improvement in electrical conductivity, thermal stability, Young's modulus and tensile strength was found, showing an optimum combination at 2 wt% loading. Drop and spin casting techniques were applied onto different substrates, and the results from deposition tests were analyzed by atomic force microscopy (AFM) and UV-vis spectroscopy. A number of parameters influencing the depositions process, namely solvent nature, sonication conditions and ozone plasma treatment, have been explored. This study paves the way for further research on conducting polymer/modified GO nanocomposites to optimize their composition and properties (i.e., transparency) for use in devices such as OSCs.