Electron Transport And Electrical Properties In Donor-Acceptor Copolymers:Methanofullerene Derivative Blends

The bulk-heterojunction photovoltaic devices fabricated from blends of donor-acceptor (D-A) copolymers as electron donor and fullerene derivatives as electron acceptor have recently attracted considerable attention. In this paper, the electron transport and electrical properties in the blends of D-A copolymer DTS-HT-C-0(F-2) and methanofullerene derivative PC71BM are investigated. From an analysis of the temperature dependence of the current density-voltage (J - V) characteristics of electron-only device based on the blends of DTS-HT-C-0(F-2) and PC71BM, it is found that consistent descriptions for the experimental measurements are obtained using both the improved extended Gaussian disorder model (IEGDM) and the extended correlated disorder model (ECDM), within which spatial correlations between the transport site energies are absent and are included, respectively. By comparing the model parameters with the typical values of organic materials, we view the more realistic intersite distance obtained using the IEGDM (3 nm) compared to the value obtained using the ECDM (0.78 nm) as an indication that in the DTS-HT-C-0(F-2):PC71BM blends correlations between the transport site energies are absent. Furthermore, it is shown that the effective mobility in the DTS-HT-C-0(F-2):PC71BM blends gradually increases with increasing temperature.