The electrical conductivity dependences of PEDOT:PSS [1], P3HT and P3HT:PCBM [2] thin films during many successive cycles of heatings-coolings in dark followed by heating-cooling cycle under illumination were studied. These investigations showed that the results are very reproducible and we distinguish very clear a difference between cycles under illumination and cycles in dark. For P3HT:PCMB films after irradiation, as in all photoconduction processes, the system needs some time to rest for coming back to the initial state. At the same irradiation, the photoelectrical properties of active layers remains stables during many cycles of heatings and coolings between 25°C and 120°C [2]. These dependencies show reversible processes and a high sensitivity of the P3HT and P3HT:PCBM to light. For a irradiation under 0.5W/m2 white light at room temperature the decrease of the resistivity as a result of light exposure is 18% for P3HT films and 20% for P3HT:PCBM blend films. By adding the fullerene molecules, in the 1:0.8 polymer:fullerene ratio, the electrical resistivity at room temperature of the blend films decrease compared to the polymer film by 40% in dark, by 35% under a irradiance of 0.5W/m2 white light and by 68% under 250W/m2 irradiance. The decrease of the resistivity with the temperature is more pronounced in the presence of light indicating a photon activated process.
[1] M.Girtan et al. Superlattices and microstructures, 46, (1-2), (2009), p.44 - 51
[2]. M.Girtan, Organic electronics 14 (1), (2013) p. 200 - 205
Speaker: M. Girtan
Photonics Laboratory, Angers University, 2, Bd. Lavoisier, 49045, Angers, France
mihaela.girtan@univ-angers.fr
Time: Friday, 12 July 2013, 11:00