In Situ Photoelectron Spectroscopy Study on the Buffer Role of Multiwalled Carbon Nanotubes against Thermal Degradation in Organic Conducting Composite Films with PEDOT:PSS

To ensure stable operation during use, the fundamental characteristics of each component in devices must be maintained. Organic electrodes of poly(3,4-ethylenedioxythiophene) polymerized with poly(4-styrenesulfonate) (PEDOT:PSS) have many deficiencies in this regard despite being widely used in various fields. Here, on the basis of various analytical results, we clearly identify not only significant denaturation of PEDOT:PSS at high temperature but also stability improvement by doping with multiwalled carbon nanotubes. As the thermal annealing temperature increases, the ratio of C-S to S-O _x bonds in PEDOT:PSS films becomes higher, owing to chemical changes and decomposition of PEDOT:PSS molecules. Further, obvious decline in work function and electrical conductivity occurs. On the other hand, the MWNT chains in a MWNT/PEDOT:PSS composite form conductive charge-carrier paths resembling a densely intertwined web. Thanks to its excellent thermal and electrical conductivity, the MWNT/PEDOT:PSS composite can serve as an electrode even after high-temperature annealing, despite denaturation of the PEDOT:PSS molecules.