The working mechanism and performance of polypyrrole as a counter electrode for dye-sensitized solar cells

Many different materials have been used as alternative counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) mainly due to the high cost of Pt CEs. So far the majority of reported work has focused on the modulation of conductivity and morphology of the CEs. The working mechanism is still unclear, specifically that of the electrocatalysis. Here it is elucidated for the first time by using polypyrrole (PPy) as the target material. The electrocatalysis is mainly comprised of formation of the weakly and strongly bonded iodine species, and formation and reduction of the intermediates. This mechanism may be valid for other CEs too. We envision that this work can help to better understand and optimize the performance of DSSCs fabricated using alternative CEs.