Future technologies will require new paradigms in design, functionality, scalability, and a reduction in power consumption to meet our global energy challenges and to reduce our environmental footprint. The quest for clean and sustainable energy sources has driven the development of solar cell technology. Organic photovoltaics (OPV) and dye‐sensitized solar cells (DSCs) are particularly attractive for low-cost, large-area applications. In both types of solar cells, charge separation is achieved at an interface between two materials. This crucial step in the generation of the desired electrical current depends critically on the properties of the interface. This work supports simulations that will advance our ability to understand, predict, and control the structure and electronic properties of functional (nanostructured) interfaces in OPV and DSCs. Employing large‐scale, massively parallel quantum mechanical simulations this investigation comprises three research thrusts, each dedicated to one of the three main interface types that are critical for the performance of OPV and DSCs: (i) organic‐organic interfaces, (ii) organic‐oxide interfaces, and (iii) organic‐graphene interfaces. The proposed research will advance the present state‐of‐the‐art in electronic structure methods and advance our ability to develop increased efficiency photovoltaics that support clean and sustainable energy.