Hole Transport Enhancing Effects of Polar Solvents on Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonic acid) for Organic Solar Cells

This study analyzed the properties of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) thin-films prepared by spin-coating solutions made with the polar solvents methanol, acetone, or N,N-dimethylformamide (DMF). A characteristic analysis was carried out for poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C(61)-butyric acid methyl ester (PCBM)-based organic solar cells (OSCs) having these modified PEDOT:PSS thin-films as the hole transport layer. The resistivity of the PEDOT:PSS thin-film obtained from the DMF solution was 4.89 × 10(-3) Ω·cm with a roughness of 3.23 × 10° nm, compared to 3.51 × 10(-1) Ω·cm and 7.72 × 10(-1) nm for a pristine PEDOT:PSS thin-film. The dipole moment increase of the solvent led to the decreased resistivity and the increased roughness and transparency of PEDOT:PSS thin-films on the structural arrangement of the polymers. Highly efficient OSCs with a power conversion efficiency of 3.47% were obtained when DMF-treated PEDOT:PSS thin-film was used as the hole transport layer.