Thermistor behavior of PEDOT:PSS thin film

The temperature-dependent resistance changing characteristics (thermistor behaviors) of a poly(3,4-ethylenedioxythophene):poly(4-styrenesulfonate) (PEDOT:PSS) thin film are investigated in the 30-100 degrees C range using Greek-cross and bar patterns. The PEDOT:PSS film was spin-coated onto a Si wafer passivated with a SiO2 layer, and a conventional dry etching technique was used to pattern the PEDOT:PSS film in conjunction with a nitride etch mask layer. Cr/Au was used for the electrode material. It was found that the characteristic temperature (T-o) and resistivity of the PEDOT:PSS film have an inversely proportional relationship with the number of coatings and the number of interfaces between multiply coated PEDOT:PSS layers. It was also found that as the number of coatings and the number of the interfaces increase, lower temperature-dependent resistance changes are observed. The temperature coefficient of resistance (TCR) value of 60 nm thick PEDOT:PSS film was slightly larger than or comparable to that of a conventional metal (Au or Pt) thermistor. The possibility of utilizing the PEDOT:PSS thin film in thermistor applications is discussed. (C) 2009 Elsevier B.V. All rights reserved.