Electron Transport in Donor-Acceptor Copolymer and Methanofullerene Derivative Organic Photovoltaic Blend

Abstract

Recently, organic photovoltaics (OPVs) based on the blends of donor–acceptor (D–A) copolymers as efficient p-type materials and fullerene derivatives as acceptors have attracted considerable attention. In this paper, electron transport and electrical properties in a blend of D–A copolymer DTS-C0(F2) 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 DTS-C0(F2):PC71BM blend, 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 semiconductors, we view the more realistic intersite distance obtained using the IEGDM (1.9 nm) compared to the value obtained using the ECDM (0.48 nm) as an indication that in DTS-C0(F2):PC71BM blend correlations between the transport site energies are absent. Furthermore, it is shown that the effective mobility in DTS-C0(F2):PC71BM blend gradually increases with increasing temperature.