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 5.0×105Vm−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 9.15mAcm−2 to 9.83mAcm−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.