Highly conductive PEDOT:PSS transparent electrode prepared by a post-spin-rinsing method for efficient ITO-free polymer solar cells

We have proposed a post-spin-rinsing method (PSRM) with polar organic solvent dimethyl sulfoxide (DMSO) to prepare highly conductive and transparent PEDOT:PSS films. The PSRM-prepared PEDOT:PSS film exhibits a conductivity of 1335Scm−1, much higher than 776Scm−1 of the PEDOT:PSS film prepared with the conventional pre-adding method (PAM). In contrast to the PAM, the PSRM with DMSO is more effective to remove the insulating PSS and push the PEDOT chains from coiled to a linear/extended-coil alignment with conformation change from a benzoid structure to a more conductive quinoid structure, leading to an enhanced conductivity of the PEDOT:PSS film. The highly conductive PEDOT:PSS film is used as transparent electrode to fabricate indium tin oxide-free polymer solar cells and a power conversion efficiency of 4.82% is achieved for polymer solar cells based on PCDTBT:PC71BM blend.