Effect of illumination on the dielectrical properties of P3HT:PC70BM nanocomposites

In this work, the effects of light-generated carriers on the dielectric properties of the structure ITO/PEDOT: PSS/P3HT:PC₇₀BM/Al were carried out. Impedance spectroscopy was performed at an applied bias equal to the open-circuit. From the real and imaginary part of the impedance, a dipolar relaxation type was observed, which decreased in the presence of light due to an increase in the electron mobility. The Cole–Cole diagram fit using a parallel model R-CPE equivalent circuit leads to the comparison of parallel resistances ( R _p) and capacitance (CPE) in dark and under illumination. The decrease of R _p is related to the increases in the photo-generated charge carrier density. The increase in the capacitance is related to the enhancement of the P3HT/PCBM interface homogeneity. (paper)