Polypyrrole/MWCNT-gr-PSSA Composite for Flexible and Highly Conductive Transparent Film

Abstract

This study compares the properties of a highly conductive polymer based on polypyrrole and multiwall carbon nanotubes (MWCNTs) grafted with poly (styrenesulfonic acid) (PPy/MWCNT-gr-PSSA) prepared for flexible indium tin oxide-free organic solar cell (OSC) anode with those of PH500 poly(3,4-ethylenedioxythiophene) : poly(styrenesulfonate) (PEDOT : PSS) in various solvents. Hydrophilic poly(styrenesulfonic acid) (PSSA) was grafted on the MWCNT surfaces to improve dispersion of the MWCNT in an aqueous solution. MWCNT-gr-PSSA was added because MWCNT acts as a conductive additive and a template for the polymerization of PPy. Polymerization yields increased as the amount of MWCNT-gr-PSSA increased and reached a maximum when 50% of MWCNT-gr-PSSA was added. The conductivity of PPy/MWCNT-gr-PSSA composite was further improved and the value reached similar to 152 S/cm with the addition of a toluenesulfonic acid (TSA)/HCl dopant mixture. To prepare a flexible OSC anode, PPy/MWCNT-gr-PSSA dissolved in solvent mixture, was coated onto a polyethylene terephthalate (PET) substrate. PPy/MWCNT-gr-PSSA was dissolved in a mixture of solvents including DMSO, NMP, EG, DEG, and glycerol of a high boiling point that was spin coated onto the PET, then annealed for 30 min at various temperatures. The conductivity of PPy/MWCNT-gr-PSSA was further enhanced with solvent treatment and annealing at temperature ranges of 100-175 degrees C. Under optimum conditions, the conductivity and transmittance of PPy/MWCNT-gr-PSSA on PET reached 602 S/cm and 84% at 550 nm, respectively. In addition, it was confirmed that the energy level and mechanical strength of the film were suitable for OSC electrode use. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 388-397, 2012