Improving the Performance of Organic Solar Cells Using an Electron Transport Layer of B4PyMPM Self-Assembled Nanostructures

The electron transport (ETL) layer improves power conversion efficiency (PCE) in organic photovoltaic cells (OPVs) through the incorporation of the cathode interfacial layers. Here, we introduce [bis-4,6-(3,5-di-4-pyridylphenyl)-2-methylpyrimidine] (B4PyMPM) as an n-type buffer layer consisting of a self-organized layer with a horizontal configuration in bulk heterojunction OPVs. It is demonstrated that self-organization of this B4PyMPM compound in which molecules adopt a horizontal orientation parallel to the organic semiconducting substrate induces a large local interfacial electric field that results in a significant enhancement of exciton dissociation. The device using B4PyMPM as an ETL layers has a significantly high open circuit voltage (V-oc = 0.64 V), good short circuit current (J(sc)= 8.24 mA/cm(2)), good fill factor (FF = 0.65) and good PCE (3.42%). The physical properties of the device have also been studied from the measurements of impedance spectroscopy and photocurrent, which directly show the mechanisms occurring inside OPVs.