A Narrow Optical Gap Small Molecule Acceptor for Organic Solar Cells

摘要

Recently, materials development in solution processable organic solar cells (OSCs) has focused upon so-called low band-gap' (or more precisely narrow optical gap) polymers specifically designed to work with fullerene acceptors in bulk heterojunctions (BHJ). Photocurrent generation in these systems is commonly thought to occur predominantly via excitation of the polymer (donor) and its subsequent oxidation by the acceptor (Figure la: Channel-I). However, it is notable that with many narrow optical gap polymers the best cell efficiencies occur when the fullerene acceptor is the dominant component in the blend. In addition, 70-PCBM, which has a larger molar extinction coefficient across a range of wavelengths than 60-PCBM, is the more effective acceptor. These results clearly suggest that light absorption by the fullerene plays an important role in charge generation.