Morphological modification induced by external electric field during solution process of organic solar cells

An electric field was externally applied on the poly(3-hexylthiophene)/[6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) blend film during the fabrication of the bulk-heterojunction (BHJ) solar cells to induce morphological modification. It influences the vertical ratio of P3HT:PCBM molecules. Because the field is applied externally to the device, its direction can be altered. When the electric field of 5.0 × 105 V m−1 was applied with the specific direction, it formed a P3HT-rich and rougher surface, compared with that of pristine active layer, to improve the performance of the inverted polymer solar cells. Hence, the current density was improved from 9.15 mA cm−2 to 9.83 mA cm−2, and power conversion efficiency increased from 3.16% to 3.51%. This finding provides guidance for morphology engineering in organic materials for higher power conversion efficiency of organic solar cells.

► An externally applied electric field induces morphological modification of P3HT:PCBM blend film.
► The external electric field treatment influences the vertical ratio of P3HT:PCBM molecules.
► It leads to a P3HT-rich and rough surface to improve the performance of the solar cells.
► The Jsc is improved from 9.15 mA/cm2 to 9.83 mA/cm2, and PCE increases from 3.16% to 3.51%.