Fullerene-Based Interlayers for Breaking Energy Barriers in Organic Solar Cells

Organic solar cells (OSCs) are lightweight, flexible, and have easy solution processability, thus making them advantageous for large-area device fabrication. The interlayer materials between the electrodes and organic active layer are vital elements for device fabrication. Recently, solution-processable fullerene derivatives have been studied intensively as efficient electrode interlayer materials for solar cell applications. In this Minireview, we summarize recent advances using fullerene derivatives as interlayers in OSCs. The examples include fullerene interlayers from small molecules to polymers, and to organic composites or organic/inorganic hybrid materials. We focus on the comprehensive efforts in developing fullerene-based interlayers and present the understanding of multiple functionalities of these materials as cathode interlayers in bulk hetero-junction (BHJ) OSCs. Our motivation is to describe our current understanding, recent progress, and outstanding issues of fullerene interlayers in OSCs, and propose future potential directions and opportunities.