Light reharvesting and enhanced efficiency of dye-sensitized solar cells based 3D-CNT/graphene counter electrodes

Abstract

3D multi-walled carbon nanotube (CNT)/graphene counter electrodes (CEs) with different transmittances were prepared using a spraying method based on CNT/graphene (MCG) aerogels. Fragments of MCG aerogels formed a 3D structure on FTO as CEs, which showed excellent performance in DSSCs. A mirror was set under the testing cells to reflect the light passed through the counter electrodes. With the increasing loading of materials at CEs, the transparency decreased and the electrocatalytic activities improved. The conversion efficiency of these CE based DSSCs surpassed that of the Pt CE (6.90%) when the transmittance was below 30% at 662 nm, and the efficiency was as high as 7.62% at a transmittance of 11%. A mirror was set under the cells, and the improvement of photocurrent density depended on the transmittance of the CEs. Re-harvesting the light increased the efficiency of the DSSCs, and the CE-based cell with the transmittance of 30% achieved the highest efficiency (7.70%).