Poly(3,4-ethylenedioxythiophene)−polystyrene sulfonate (PEDOT:PSS) has been extensively investigated as a polymeric electrode material for flexible, stretchable electronic devices. The addition of dimethyl sulfoxide (DMSO) increases the conductivity of PEDOT:PSS. However, the addition can also alter the surface electronic structure and affect its energy-level alignment with organic semiconductors, which is crucial for device performance. In this study, the impact of DMSO on the energy-level alignment of the PEDOT:PSS/C₆₀ interface was investigated. In-situ ultraviolet and X-ray photoelectron spectroscopy analyses revealed that DMSO increases the work function of PEDOT:PSS by 0.15 eV and alters the electron and hole-injection barriers to C₆₀. In pristine PEDOT:PSS, the electron and hole-injection barriers were 0.72 and 1.53 eV, respectively. In DMSO-modified PEDOT:PSS, these barriers were 0.81 and 1.44 eV, respectively. These results highlight the effect of additive modifications on the energy-level alignment of PEDOT:PSS.

Keywords: Energy-level alignment, In-situ ultraviolet photoelectron spectroscopy, Poly(3,4-ethylenedioxythiophene)&minus,polystyrene sulfonate, Dimethyl sulfoxide, C₆₀