Two-Step Improvement of Thermoelectric Properties of PEDOT:PSS Films by Femtosecond Laser and Ammonia Vapor Atmosphere Treatment

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) exhibits exceptional optical properties and flexibility. Additionally, its aqueous suspension demonstrates commercial viability, making this material particularly suitable for low-cost solution processing applications for flexible electronic devices. However, the relatively low initial conductivity (σ) of PEDOT:PSS (∼1 S cm –1 ) makes it unsuitable for direct application in flexible thermoelectric devices. Herein, we report a two-step approach to improve the thermoelectric properties of PEDOT:PSS films by a femtosecond laser and ammonia vapor atmosphere treatment. First, femtosecond laser treatment reduces the PSS content and causes the benzoquinone conformational transformation of the PEDOT molecular chain. Although it increases the electrical conductivity (σ), it leads to a decrease in the Seebeck coefficient ( S ). The subsequent ammonia vapor atmosphere treatment precisely regulates the PEDOT dedoping level, utilizes the binding effect between NH 4 + and PSS – to weaken the interaction force between the two, enhances the S, and thereby enhances the overall thermoelectric performance. The treated PEDOT:PSS films showed S, σ, and corresponding power factor (PF) values of 26.15 μV K –1, 413.19 S cm –1, and 28.24 μW·m –1 ·K –2, respectively. The prepared organic thermoelectric device shows an output voltage of 5.3 mV at a temperature difference of 40.6 °C.