Control of Porphyrin Dye Aggregation Using Bis(4-pyridyl)Alkanes in Dye Sensitized Solar Cells

Abstract

The aggregation of sensitizer molecules on the surface of photoanode is a serious issue that can affect the photovoltaic performance of dye-sensitized solar cells. Prevention of dye agglomeration, therefore, is critical. Traditional methods of aggregation control are either synthetically challenging or technologically difficult and expensive. In this article, the use of bis(4-pyridyl)alkanes to control porphyrin dye aggregation is presented. Three bis(4-pyridyl)alkanes – bis(4-pyridyl)butane L4, bis(4-pyridyl)octane L8 and bis(4-pyridyl)decane L10 were synthesized. These bis(4-pyridyl)alkane ligands are axially attached to the metallic center of synthesized porphyrin dye P. The complexes was obtained by mixing the solutions of dye P and each ligand (L) in 2:1 ratio 1 h before the soaking step. As a result three cells were prepared: P-L4, P-L8 and P-L10. The performance of these cells were compared with a reference cell which was prepared from porphyrin dye P only. IPCE analysis demonstrated the highest dye load in P-L4 cell which was ascribed to lowered dye aggregation. Photovoltaic analysis showed improved short circuit current density due to suppressed dye aggregation caused by the complexation of the porphyrin dye P with the linker L4. As a result the overall cell efficiency increased to 42% demonstrating the successful utilization of the (4-pyridyl)alkane linker complexes with porphyrin dye.