Single-step treatment to improve conductivity of PEDOT:PSS by hydrobromic acid solution for application of transparent electrode

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) is the most well-known organic conducting material due to tunable conductivity, high transparency, facile processability and stability. Single-step post-treatment by DMSO solvent and hydrobromic acid solution in DMSO improved the electrical conductivity of pristine PEDOT:PSS from 0.4 S/cm to 632 S/cm and 1813 S/cm, respectively. Mechanism of conductivity improvement is associated to diffusion of DMSO solvent and HBr-DMSO solution into PEDOT:PSS which induce charge screening by forming hydrogen bonding and weaken the electrostatic interactions of conducting PEDOT and insulating PSS. This affect the phase separation of PEDOT and PSS, and washing away the separated excess-PSS result in conductive PEDOT grains observed by increased surface roughness through AFM height images. Analysis of Raman and vis-NIR spectra and Hall-effect measurement confirmed the improvement in oxidation state of PEDOT:PSS by HBr-DMSO treatment. Treated films showed very low sheet resistance of 85 omega/? with high transparency of 90% leading to figure of Merit (FOM) of 38 for transparent electrode. Treated film as anode of organic solar cell have shown better photovoltaic performance with PCE of 2.64% compared to PCE of 0.055% by untreated PEDOT:PSS. These results suggest that the treated PEDOT:PSS can replace ITO electrode in organic optoelectronic applications.

Automated summary

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) is an organic conducting material with tunable conductivity, high transparency, facile processability and stability. Treatment with DMSO solvent and hydrobromic acid solution in DMSO significantly improves the electrical conductivity of PEDOT:PSS. The mechanism of the conductivity improvement is attributed to the diffusion of DMSO and HBr-DMSO solution into PEDOT:PSS, resulting in charge screening and weakening of the electrostatic interactions. The treated PEDOT:PSS films exhibit low sheet resistance and high transparency, making them suitable for optoelectronic applications such as organic solar cells.