Significant enhancement in the conductivity of highly transparent PEDOT:PSS thin film through maleic acid treatment

Abstract The conductivity of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS, a conducting polymer) thin film is enhanced by simply maleic acid treatment. Here, we have investigated the conductivity enhancement with the variation of maleic acid concentration. The conductivity enhances up to 1.0 M maleic acid concentration and decreases afterward. The optimum conductivity is obtained as 9.35 S cm –1 , which is nearly 263 times more compared to the pristine PEDOT:PSS film. The conductivity of the film also depends upon the treating temperature. Therefore, the effect of different treating temperatures on the conductivity enhancement is studied, and the optimum temperature is found to be 140 °C. Maleic acid-treated PEDOT:PSS films also exhibit high transmittances, i.e., ≈ 90%–84% in the visible region. The mechanism related to the conductivity enhancement and other related information are collected through different spectroscopic and microscopic measurements. Besides, frequency-dependant impedance and electrochemical activity of maleic acid-treated PEDOT:PSS films are also performed. The interaction of maleic acid with PEDOT:PSS promotes the reduction of ionic interaction between PEDOT and PSS chains, resulting in the phase separation between PEDOT and PSS. As a result, the PSS – turn into neutral PSSH and are rinsed away by water, which supports the morphological change and the conductivity enhancement due to the conformational change of coil-like PEDOTs to elongated and better-connected PEDOT chains.