Atmospheric-pressure surface-diffusion dielectric-barrier discharge (SDDBD) plasma surface modification of PEDOT:PSS

Atmospheric-pressure surface-diffusion dielectric-barrier discharge (SDDBD) plasma is used to treat poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) inside a nitrogen-filled glove box. The SDDBD-treated PEDOT:PSS is then used as the hole transport layer of an inverted planar perovskite solar cell (PSC). Electrons and reactive ions in plasma can react with PEDOT:PSS. The resistivity of PEDOT:PSS decreases and then increases as SDDBD treatment time increases. This trend well corresponds to the PEDOT/PSS ratio, as indicated by the change of the X-ray photoelectron spectroscopy (XPS) S2p binding energy peak area ratio upon SDDBD treatment. Plasma treatment could eliminate part of excess PSS on the surface to uncover the PEDOT phase and change the PEDOT/PSS ratio, thereby altering the resistivity and work function of PEDOT:PSS. This influences the charge transport and charge extraction of PSCs, leading to a PSC with improved cell efficiency and reduced hysteresis. The best efficiency of PSC is achieved with 30-s SDDBD treatment.