Effect of UV–ozone treatment on electrical properties of PEDOT:PSS film

We reveal the effect of UV–ozone treatment on the electrical properties of poly (styrenesulfonate) doped poly (3,4-ethylenedioxythiophene) (PEDOT:PSS) film by clarifying the respective roles of UV light irradiation and exposure to ozone gas. The UV–ozone treatment induced increases in both work function and resistivity. Furthermore, the film thickness was reduced at a rate of 0.13 nm/min. The ozone-exposed films also exhibited a marked increase in the work function. However, such variations were not observed in the resistivity and film etching. Angle resolved X-ray photoelectron spectroscopy revealed that the main role of the UV light was to decompose the chemical bonds in the PEDOT:PSS film, resulting in a resistivity increase and film etching. In contrast, the ozone and atomic oxygen were absorbed and oxidized the surface, which was responsible for the increase in the work function. Due to these different functions, UV–ozone treatment is capable of controlling the work function and resistivity of PEDOT:PSS film thus allowing them be adjusted to the device application.