In‐Situ Photoelectron Spectroscopy Study on the Air Degradation of PEDOT:PSS in Terms of Electrical and Thermoelectric Properties

Abstract Despite excellent electrical and mechanical properties, practical application of poly(3,4‐ethylenedioxythiophene) polymerized with poly(4‐styrenesulfonate) (PEDOT:PSS) face the challenge of ensuring air stability in electronic industry. Here, degradation mechanism of PEDOT:PSS‐based films in air is clearly demonstrated through X‐ray/ultraviolet photoelectron spectroscopy (XPS/UPS) and its depth‐profiling technique. As the duration of air‐exposure increases, the PEDOT:PSS‐based films alter molecular structures with the formation of SO x bond in PEDOT and CN x bond growth, changing ratios of insulating part (PSS − , PSSH, oxidized PEDOT) to conducting part and deteriorating their electrical conductivities. These transition behaviors are similar in all PEDOT:PSS‐based films regardless of additives such as dopant or multi‐walled carbon nanotube. Additionally, methanol treatment to various PEDOT:PSS‐based films for inducing conformational change between PEDOT and PSS molecules, partly restore the electrical properties of the denatured PEDOT:PSS films. Finally, thermoelectric properties of the PEDOT:PSS‐based films are characterized by investigating the effects of air‐aging and methanol treatment on electrical conductivities, Seebeck coefficients, and power factors. To sum up, this study provides a useful guideline for establishing a strategy to ensure air stability of PEDOT:PSS‐based films by clarifying the degradation mechanism and property recovery methods.