Choose a reasonable counter electrode catalyst toward a fixed redox couple in dye-sensitized solar cells

We evaluate the activities of different counter electrode (CE) catalysts on the regeneration of various redox couples in dye-sensitized solar cells (DSCs). Pt-free CE materials such as poly (3,4-ethylenedioxythiophene) (PEDOT), carbon spheres, and tantalum carbide (TaC) exhibit high catalytic activities toward the I3−/I− and Co3+/2+ redox couples with no cost concerns, although Pt remains the ideal CE catalyst. An opposite trend is observed for organic redox couple of di-5-(1-methyltetrazole) disulfide/5-mercapto-1-methyltetrazole sodium salt (T2/T−). Indeed, Pt-free CE catalysts are more suitable for the organic redox couple. Moreover, several methods have been proposed to enhance the catalytic activities of Pt-free CE catalysts. Synthesis of a composite catalyst is an effective path to enhance the catalytic activity of TaC CE. In PEDOT CE, the constructed porous network structure is essential for achieving high catalytic activity. Tuning the diameter, design hollow structure and open-ended surface can strongly affect their catalytic behavior of the carbon spheres CE. After optimization, the cobalt electrolyte based DSCs yield excellent power conversion efficiency (PCE) of 10.61% with open-ended carbon spheres (OCS) CE. Therefore, we can enhance the PCE value and cut the cost of DSCs by selecting a suitable low cost CE catalyst toward a fixed redox couple.