Effect of self-assembly supramolecules on the electrical properties of polyaniline based hole transport layer

To increase the power conversion efficiency of organic solar cells (OSCs), polyaniline (PANI) based film was introduced to the hole transport layer (HTL) of OSCs in this study. Two steps were applied to obtain high conductivity and water solubility of PANI. First, self-assembly supramolecules (SAS) were blended with PANI to improve crystallinity. Second, poly(styrenesulfonic acid) (PSSA), hydrophilic polymer, was grafted on the PANI surface to improve dispersion in aqueous solutions and to increase the conductivity of PANI through a self-doping system. As a result, the conductivity of PANI based film (PANI/SAS16-gr-PSSA) could be improved and reached to 0.81 S/cm in a nano layer state, since this innovative method prevents the polymer chains from the recoiling of PANI. The conductivity of PANI/SAS16-gr-PSSA is higher than that of poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) (0.01 S/cm) and PANI-gr-PSSA (0.17 S/cm). The energy level of the prepared PANI/SAS16-gr-PSSA nano layer is approximately 4.83 eV, indicating that it is suitable for a hole transport layer between the ITO electrode and photoactive layer. The OSCs device made of PANI based HTL prepared in this study shows a high power conversion efficiency of approximately 3.4%, which is higher than that of OSCs with PEDOT:PSS (2.8%) and PANI-gr-PSSA (3.0%) layer.