Simultaneous improvement in electrical conductivity and Seebeck coefficient of PEDOT:PSS by N2 pressure-induced nitric acid treatment

May Thu Zar Myint; Masaki Hada; Hirotaka Inoue; Tatsuki Marui; Takeshi Nishikawa; Yuta Nishina; Susumu Ichimura; Masayoshi Umeno; Aung Ko Ko Kyaw; Yasuhiko Hayashi

doi:10.1039/c8ra06094k

Simultaneous improvement in electrical conductivity and Seebeck coefficient of PEDOT:PSS by N₂ pressure-induced nitric acid treatment

RSC Adv. 2018 Oct 30;8(64):36563-36570. doi: 10.1039/c8ra06094k. eCollection 2018 Oct 26.

Authors

Affiliations

¹ Graduate School of Natural Science and Technology, Okayama University 3-1-1 Tsushima-naka, Kita Okayama 700-8530 Japan hayashi.yasuhiko@okayama-u.ac.jp.
² Nagoya Industries Promotion Corporation 3-4-41 Rokuban, Atsuta Nagoya 456-0058 Japan.
³ C's Techno. Inc. Anagahora, Shimoshidami, Moriyama Nagoya 463-0003 Japan.
⁴ Department of Electrical and Electronic Engineering, Southern University of Science and Technology Shenzhen 518055 P. R. China aung@sustc.edu.cn.
⁵ Shenzhen Planck Innovation Technologies Pte Ltd Ganli 6th Road, Longgang Shenzhen 518112 China.

Abstract

As a thermoelectric (TE) material suited to applications for recycling waste-heat into electricity through the Seebeck effect, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonic acid) (PEDOT:PSS) is of great interest. Our research demonstrates a comprehensive study of different post-treatment methods with nitric acid (HNO₃) to enhance the thermoelectric properties of PEDOT:PSS. The optimum conditions are obtained when PEDOT:PSS is treated with HNO₃ for 10 min at room temperature followed by passing nitrogen gas (N₂) with a pressure of 0.2 MPa. Upon this treatment, PEDOT:PSS changes from semiconductor-like behaviour to metal-like behaviour, with a simultaneous enhancement in the electrical conductivity and Seebeck coefficient at elevated temperature, resulting in an increase in the thermoelectric power factor from 0.0818 to 94.3 μW m^-1 K^-2 at 150 °C. The improvement in the TE properties is ascribed to the combined effects of phase segregation and conformational change of the PEDOT due to the weakened coulombic attraction between PEDOT and PSS chains by nitric acid as well as the pressure of the N₂ gas as a mechanical means.