Highly conductive PEDOT:PSS films prepared through a treatment with zwitterions and their application in polymer photovoltaic cells

This paper reports the significant conductivity enhancement of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films through a treatment with aqueous solutions of zwitterions for the first time. The conductivity enhancement was dependent on the structure of the zwitterions and the experimental conditions during the treatment, such as the concentration of the zwitterions and the temperature. Conductivity enhancement from 0.2 to 92.4 S cm(-1) was observed on PEDOT:PSS films after a zwitterion treatment. The chemical and physical characterizations indicate the lowering of the energy barrier for charge hopping across the PEDOT chains, the loss of poly(styrene sulfonate) acid (PSSH) chains from the PEDOT:PSS film, and the conformational change of the PEDOT chains after the zwitterion treatment. These highly conductive PEDOT:PSS films could be used to replace indium tin oxide (ITO) as the transparent anode of polymer photovoltaic cells (PVs). Power conversion efficiency as high as 2.48% was observed on the polymer PVs with a zwitterion-treated PEDOT:PSS film as the transparent anode.