Improving photovoltaic properties via electric-field-induced orientation of conjugated polymer

A high electric field is applied to polarize the undoped MEH-PPV and the MEH-PPV: C60 composite thin film in the process of spin-coating. Due to the polarization causing the orientation of the MEH-PPV chains, the resulting thin-film devices show improved photovoltaic properties. For undoped MEH-PPV devices, oriented under the electric field of 6×103 V cm−1, the short-circuit current ( J sc ) and the external quantum efficiency (EQE) are enhanced by a factor of 2.5 and 2, respectively. For MEH-PPV–fullerene composite devices, oriented under the same field, the J sc and the EQE are improved by a factor of 1.8 and 1.7, respectively.