Interfacial Materials for Organic Solar Cells

Organic solar cell (OSC) is one of the promising photovoltaic technology for next generation low-cost renewable energy sources. The power conversion efficiencies (PCE) of OSCs have reached above 14% in single-junction and ~17% in tandem OSCs. This rapid increase in the performance is mostly profited from the synergetic advances in rational molecular design, device processing and interfacial layer modifications. In addition to the development of efficient photoactive materials, interfacial design plays a crucial role in the improvement of device performance and stability. Most importantly, the interfacial layer is responsible for establishing good ohmic contact in the device, thus minimize the resistance, interfacial recombination and improve charge selectivity. In this chapter, we present the recent development in the electron and hole transporting interfacial materials design for both single-junction and tandem OSCs. Special attention will be paid to the design principles of interfacial materials which includes inorganic metal oxides, composite materials, oligomeric and polymeric molecules and their use as cathode and anode interlayer for high efficiency devices. The structure-property relationships of various interfacial materials will be analyzed as an approach towards high performance OSCs. Finally, we will discuss the current challenges with possible solutions and perspectives for performance enhancement in OSCs.