title: Solution-processed poly(3,4-ethylenedioxythiophene) thin films as transparent conductors: effect of p-toluenesulfonic acid in dimethyl sulfoxide.
abstract: Conductivity enhancement of thin transparent films based on poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) by a solution-processed route involving mixture of an organic acid and organic solvent is reported. The combined effect of p-toluenesulfonic acid and dimethyl sulfoxide on spin-coated films of PEDOT-PSS on glass substrates, prepared from its commercially available aqueous dispersion, was found to increase the conductivity of the PEDOT-PSS film to ∼3500 S·cm(-1) with a high transparency of at least 94%. Apart from conductivity and transparency measurements, the films were characterized by Raman, infrared, and X-ray photoelectron spectroscopy along with atomic force microscopy and secondary ion mass spectrometry. Combined results showed that the conductivity enhancement was due to doping, rearrangement of PEDOT particles owing to phase separation, and removal of PSS matrix throughout the depth of the film. The temperature dependence of the resistance for the treated films was found to be in accordance with one-dimensional variable range hopping, showing that treatment is effective in reducing energy barrier for interchain and interdomain charge hopping. Moreover, the treatment was found to be compatible with flexible poly(ethylene terephthalate) (PET) substrates as well. Apart from being potential candidates to replace inorganic transparent conducting oxide materials, the films exhibited stand-alone catalytic activity toward I(-)/I3(-) redox couple as well and successfully replaced platinum and fluorinated tin oxide as counter electrode in dye-sensitized solar cells.
authors.affiliation: Centre of Excellence in Nanoelectronics, ‡Department of Chemistry, §Centre for Research in Nanotechnology & Science, and ∥Department of Electrical Engineering, Indian Institute of Technology Bombay , Mumbai 400076, India.
authors.forename: Smita
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Rekha
authors.initials: R
authors.lastname: Singh
authors.forename: Sreelekha
authors.initials: S
authors.lastname: Gopinathan
authors.forename: Sengottaiyan
authors.initials: S
authors.lastname: Murugan
authors.forename: Suhas
authors.initials: S
authors.lastname: Gawali
authors.forename: Biswajit
authors.initials: B
authors.lastname: Saha
authors.forename: Jayeeta
authors.initials: J
authors.lastname: Biswas
authors.forename: Saurabh
authors.initials: S
authors.lastname: Lodha
authors.forename: Anil
authors.initials: A
authors.lastname: Kumar
keywords: PEDOT−PSS; conductivity enhancement; dye-sensitized solar cell; organic acid treatment; transparent conducting polymer