The electrochromic polymer poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT-PSS) spin-coated on ITO/glass was patterned with a soft lithographic method in order to diffract the incident light and thereby modify absorption of light by the film to improve the electrochromic efficiency of the polymer. The absorbance peak at around 610 nm was found to be much higher in the patterned PEDOT-PSS film than the one observed in the unpatterned film. Values of coloration efficiencies varying from 107 to 174 cm(2)/C were obtained for three different unpatterned PEDOT-PSS films, whereas for three different patterned PEDOT-PSS films higher values ranging from 211 to 371 cm(2)/C were found. These increased values of the electrochromic efficiencies are attributed to diffraction. (C) 2004 The Electrochemical Society.