Organic thermoelectric (TE) attracts considerable interest as a next-generation energy conversion technology; however, its practical application is still restricted by low power factors. Herein, we report a generally applicable solvent-combination doping method for improving TE properties of conjugated polymers (CPs). Residual solvents in a ternary solvent enlarged the free volume in the CP films. This beneficial effect boosted both dopant diffusion efficiency and charge carrier density in the doped films, resulting in the remarkable enhancement of electrical conductivity in the CPs. When the doped CP films processed with a ternary solvent were applied to TE devices, excellent power factors were achieved, attributed to a durable Seebeck coefficient along with ultrahigh electrical conductivity.
S.E.Y. Y.K, J.I, and J.L contributed equally to this work. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (NRF-2021R1A2C1007304, NRF-2021K1A4A7A03093851, 2019R1A6A1A11051471, 2021R1A5A6002853, 2020R1A6A1A03038697, 2020R1C1C1012690, NRF-2021R1A2C4002030, and 2021R1C1C1010266). The computational resources were provided by the Korea Institute of Science and Technology Information (KISTI) (KSC-2021-CRE-0518). S.K.K. H.H.C. B.-G.K. and J.H.K. conceived the idea, designed the research, and wrote a manuscript. S.E.Y. fabricated devices and characterized electrical conductivity and thermoelectric properties of doped polymer films with support from J.I. S.Y.L. D.J. J.Y.S. J.K. T.K. H.S. and K.K. Y.K. C.J.K. I.M. and J.P. synthesized the polymers and performed UV-vis and ESR spectra measurements. J.L. and Y.J.G. conducted the computational calculations. K.K. S.K.K. H.H.C. B.-G.K. and J.H.K. supervised this project. All authors discussed the results. The authors declare no competing interests. We support inclusive, diverse, and equitable conduct of research.This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government ( NRF-2021R1A2C1007304 , NRF-2021K1A4A7A03093851 , 2019R1A6A1A11051471 , 2021R1A5A6002853 , 2020R1A6A1A03038697 , 2020R1C1C1012690 , NRF-2021R1A2C4002030 , and 2021R1C1C1010266 ). The computational resources were provided by the Korea Institute of Science and Technology Information (KISTI) ( KSC-2021-CRE-0518 ).
