New conjugated polymer/fullerene nanocomposite for energy storage and organic solar cell devices: Studies of the impedance spectroscopy and dielectric properties

Abstract

A new conjugated polymer poly(1,4-phenylene−ethynylene)-alt-poly(1,4-phenylene-vinylene) s (PPE−PPVs) abbreviated P18-8_18-8 is blended with fullerene (PCBM) to fabricate an organic solar cell with a structure ITO/PEDOT:PSS/P18-8_18-8/PCBM/LiF/Al. Current density-voltage (J-V) characteristics, complex impedance (Z* =Z′-jZ′′), dielectric loss (ε′′), dielectric loss tangent (tan(δ)), and complex electric modulus (M*= M′+jM′′) were investigated in dark and under illumination. As the frequency increase, the ε′′was decreased for all applied voltages in dark due to the deformation and relaxation polarization contributions. The lower M′ values found at low frequency region were attributed to the long-range mobility of charge carriers. Furthermore, the variation of M′′ with angular frequency obtains its maximum value at all applied voltages, causing a peak at a certain frequency. Frequency-dependent conductance (σ) displays a power-law dependence “s” which increased with applied voltage, and it is higher than unity. At bias voltage equal to 0 V and under illumination, the capacity at the interface between the polymer and the fullerene is electrically more homogeneous. The conductivity increased because the trapped charges acquire the necessary energy to escape from the interface and the hopping time found was reduced.