Self-organized buffer layers in organic solar cells

A fullerene derivative with a fluorocarbon chain is applied in bulk-heterojunction polymer solar cells (see figure). When a small amount of F-PCBM is mixed in, it spontaneously migrates to the surface of the organic layer during spin-casting owing to the low surface energy of the fluorocarbon. A very thin buffer layer between the polymer and the metal electrode is formed in one step, resulting in improved photovoltaic performance.