Enhanced thermoelectric performance of PEDOT: PSS films via ionic liquid post-treatment

Thermoelectric(TE) energy harvesting can effectively convert waste heat into electricity, which is a crucial technology to solve energy concerns. As a promising candidate for energy conversion, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS) has gained significant attention owing to its easy doping, high transparency, and solution processability. However, the TE performance of PEDOT:PSS still needs to be further enhanced. Herein, different approaches have been applied for tuning the TE properties:(i) direct dipping PEDOT:PSS thin films in ionic liquid;(ii) post-treatment of the films with concentrated sulfuric acid(H2SO4), and then dipping in ionic liquid. Besides, the same bis(trifluoromethanesulfonyl)amide(TFSI) anion and different cation salts, including 1-ethyl-3-methylimidazolium(EMIM+) and lithium(Li+), are selected to study the influence of varying cation types on the TE properties of PEDOT:PSS.The Seebeck coefficient and electrical conductivity of the PEDOT:PSS film treated with H2SO4EMIM:TFSI increase simultaneously, and the resulting maximum power factor is 46.7 μW·m-1·K-2, which may be attributed to the ionic liquid facilitating the rearrangement of the molecular chain of PEDOT. The work provides a reference for the development of organic films with high TE properties.