Improved Alignment of PEDOT:PSS Induced by in-situ Crystallization of "Green" Dimethylsulfone Molecules to Enhance the Polymer Thermoelectric Performance

Qiang Zhu; Erol Yildirim; Xizu Wang; Xiang Yun Debbie Soo; Yun Zheng; Teck Leong Tan; Gang Wu; Shuo-Wang Yang; Jianwei Xu

doi:10.3389/fchem.2019.00783

Improved Alignment of PEDOT:PSS Induced by in-situ Crystallization of "Green" Dimethylsulfone Molecules to Enhance the Polymer Thermoelectric Performance

Front Chem. 2019 Nov 15:7:783. doi: 10.3389/fchem.2019.00783. eCollection 2019.

Authors

Qiang Zhu¹, Erol Yildirim², Xizu Wang¹, Xiang Yun Debbie Soo¹, Yun Zheng¹, Teck Leong Tan², Gang Wu², Shuo-Wang Yang², Jianwei Xu^{1

3}

Affiliations

¹ Institute of Materials Research and Engineering, ASTAR (Agency for Science, Technology and Research), Singapore, Singapore.
² Institute of High Performance Computing, ASTAR (Agency for Science, Technology and Research), Singapore, Singapore.
³ Department of Chemistry, National University of Singapore, Singapore, Singapore.

Abstract

Dimethylsulfone (DMSO₂), a small organic molecule, was observed to induce the alignment of poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonate) (PEDOT:PSS) via in-situ crystallization in PEDOT:PSS mixture, which was verified by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and atomic force microscopy (AFM). A chemically stable dopant, DMSO₂, remarkably raised the electrical conductivity of the PEDOT:PSS film, which was fabricated from pre-mixed solution of PEDOT:PSS and DMSO₂, up to 1080 S/cm, and more importantly, such a PEDOT:PSS film showed a long-term humidity stability and it retained near 90% electric conductivity after 60 days, suggesting DMSO₂ is promising for an eco-friendly alternative to replace dimethyl sulfoxide (DMSO), ethylene glycol (EG) and various acids dopants that have been widely employed to dope and post-treat PEDOT:PSS. Pairwise interaction energies and free energy of solvation between PEDOT:PSS and DMSO₂ were calculated by first-principles and molecular mechanics, respectively, revealing the mechanism of DMSO₂ in enhancing the electrical conductivity.

Keywords: PEDOT:PSS; crystallization; dimethylsulfone; polymer alignment; thermoelectric.