Effect of visible light on the electrical conductivity of conductive grade PEDOT:PSS

Abstract This study systematically investigated the impact of visible light on the electrical conductivity of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films by varying exposure time, intensity and energy/wavelength of visible light. The electrical conductivity of the light-treated films was quantitatively assessed using a four-point probe method across a temperature range of 250 K to 350 K. The findings revealed that the electrical conductivity of the polymer increases as the visible light treatment time increased from 0 to 180 min. However, further exposure beyond this threshold, 180 min, did not yield any significant enhancement in electrical conductivity, suggesting a saturation in the photo physics, photoexcitation of electron from a π to a π* orbital and electronic structure, of the PEDOT component that enhances conductivity of the material. Conversely, an inverse relationship was observed between the electrical conductivity and the distance of the polymer film from the illumination source, i.e., conductivity of the polymer increases with light intensity or illuminance. Furthermore, the study investigated that the electrical conductivity of the PEDOT:PSS tends to depend on the energy or wavelength of the light source. Notably, the electrical conductivity of the PEDOT:PSS obtained by blue light exposure was superior to that of white light exposure; and unilluminated (dark) condition of the polymer film resulted the least conductivity. This enhancement of PEDOT:PSS electrical conductivity, by increasing photon intensity/time of exposure or energy, appears to indicate an interesting insight and implications on the device physics of electronics and optoelectronic devices including organic/hybrid based photovoltaic cells, light-emitting diodes (LEDs) and related devices that uses the polymer as a device layer.