The Effects of Dilute Sulfuric Acid on Sheet Resistance and Transmittance in Poly(3,4-thylenedioxythiophene): Poly(styrenesulfonate) Films

Abstract

The conductivity of poly(3,4-thylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) films by adding various molar concentrations of sulfuric acid (H 2 SO 4 ) was improved and studied in this paper. The sheet resistance of the doped PEDOT: PSS film was enhanced with increasing the ratio of H 2 SO 4 , but it drops after the maximum sheet resistance. The reason for this phenomenon is resulting from the fact that the H 2 SO 4 preferentially react with the sorbitol which is so-called the pinacol rearrangement. The nonconductive anions of some PSS − were substituted by the conductive anions of hydrogen sulfate (HS<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mrow><mml:msup><mml:mrow><mml:msub><mml:mrow><mml:mtext>O</mml:mtext></mml:mrow><mml:mrow><mml:mn fontstyle="italic">4</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>) when the residual H 2 SO 4 reacted with PSS. In addition to the substitution reaction, PEDOT chains were increasingly aggregated with increasing the ratio of H 2 SO 4 . After doped H 2 SO 4 , the sheet resistance of H 2 SO 4 -doped PEDOT: PSS film is improved nearly 36%; the surface roughness is reduced from 1.268 nm to 0.822 nm and the transmittance is up to 91.9% in the visible wavelength range from 400 to 700 nm.