Low-cost and flexible poly-(3,4-ethylenedioxythiophene) based counter electrodes for efficient energy conversion in dye-sensitized solar cells

A roll-to-roll slot die coating process was used to deposit PEDOT:PSS on PET and the resulting composite films were evaluated for use as counter electrodes in dye-sensitized solar cells (DSCs). The effect of depositing an additional layer of electropolymerized PEDOT onto the flat PEDOT/PET electrodes was also studied. Counter electrodes and complete DSCs were characterized by steady-state current-voltage, electrochemical impedance spectroscopy and IPCE measurements. Evidence that the PEDOT-based counter electrode can modify the electrolyte solution composition, probably by increasing the proton concentration, is presented. The overall cell performance under 1 Sun illumination is improved by addition of an electropolymerized layer of PEDOT to flat PEDOT/PET counter electrodes, but both remain inferior to platinized FTO. Under 0.2 Sun illumination, devices employing counter electrodes with electropolymerized PEDOT on a PEDOT/PET substrate (named as EP/PEDOT/PET) perform almost similarly to those with platinized FTO counter electrodes, suggesting that EP/PEDOT/PET electrodes may be useful in DSCs designed for low light (e.g. indoor) operation, especially considering the low costs of PEDOT and the roll-to-roll and electropolymerization processes.