Calamatic liquid crystal blends for organic photovoltaics

摘要: Four different perylene-based electron-acceptors having similar electron affinities, but different thermotropic phases are blended with nematic liquid crystalline electron-donors with a fluorene-thiophene structure to form single layer photovoltaic devices. Best results are obtained when the nematic donor is mixed with an amorphous acceptor to give a supercooled nematic glass at room temperature. Atomic force microscopy operating in the phase contrast mode reveals phase separation on a nanometer scale with a broad distribution of domain sizes peaking at 26 nm. We correlate the morphology of the different blends with the performance of the photovoltaic devices. Power conversion efficiencies up to 0.9 % are obtained with excitation at 470 nm.