The effect of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid (PEDOT:PSS) modified with an amphiphilic fluoro compound was investigated on the performance of flexible organic solar cells in bilayer geometry and using substrate based on poly(ether-imide) (PEI) with ITO films with low resistivity and high optical transmittance. The poly[9,9'-dioctyl-fluorene-co-bithiophene] (F8T2) polymer and fullerene (C-60) were used as electron donor and acceptor materials, respectively. The spin-casted PEDOT: PSS films had its sheet resistance reduced from 7 M Omega sq(-1) to 40 k Omega sq(-1) after a single step treatment with hexafluoroacetone (HFA), reflecting in an enhancement of power conversion efficiency in the photovoltaic cells from 0.45% up to 1.30%. (C) 2013 Elsevier B. V. All rights reserved.