Over the past two decades, the science and engineering of organic semiconducting materials have advanced very rapidly, leading to the demonstration and optimization of a range of organics-based solid-state devices, including organic light-emitting diodes, field-effect transistors, photodiodes, and photovoltaic cells. Particularly attractive for organic semiconductors are flexible plastic substrates that can lead to applications and consumer products with lower cost, highly flexible form factors, and light weight. These attributes, combined with the ability to tune the physical properties of organic (macro)molecules by fine tuning their chemical structure, constitute the main drivers boosting research and industrial interest in organic photovoltaics. Critical to the operation of organic solar cells are the interfaces between (metal or conducting oxide) electrodes and organic layers and between organic layers. This presentation will focus on the computational characterization and optimization of the interfacial properties between the electron donor component (usually a conjugated polymer) and the electron acceptor component (usually a fullerene derivative).