Fabrication Method for Spin-Coating ITO-Competitive PEDOT:PSS onto PVDF Film

Abstract

This paper shows a four-order reduction of magnitude in sheet resistance for spin-coating poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) onto polyvinylidene fluoride (PVDF) film for a final sheet resistance comparable to commercially available indium tin oxide- (ITO-) coated PVDF film. The resulting PEDOT:PSS transparency is 10% less than the transparency for ITO:PVDF. This is done by the combination of four techniques from the literature including (i) varying layers, (ii) plasma etching, (iii) post-treatment submersion in an ethylene glycol (EG) bath, and (iv) adding EG and a surfactant to the PEDOT:PSS solution. The PEDOT:PSS sheet resistance falls from over 3 megaohms/sq to between 600 and 150 ohms/sq depending on the number of layers. The one-layer sample has a sheet resistance of 600 ohms/sq and an optical transparency of about 76%, and the five-layer sample has a sheet resistance of 150 ohms/sq and an optical transparency of about 50%. These results reported here make PEDOT:PSS an attractive option for transparent piezoelectric micromachined ultrasonic transducer (PMUT) array applications.