Enhanced electrocatalytic activity of Cu₂S-polyaniline heterostructure counter electrode for quantum dot-sensitized solar cells

The Cu₂S-Polyaniline (Cu-P) counter electrode (CE) was prepared by electropolymerization of polyaniline (PANI) on a FTO/Cu₂S film. The surface morphology and crystallinity of the counter electrode were examined. The FTO/Cu-P CE provided significantly enhanced electrochemical activity and a faster charge transfer rate compared to the platinum (Pt), Cu₂S, PANI, and PANI-Cu₂S (P-Cu) CEs because of the synergistic effect between the high carrier mobility of PANI and the good electrocatalytic activity of Cu₂S on the polysulfide electrolyte. Besides, the FTO/Cu-P CE exhibited excellent electrochemical stability, due to the strong interaction between the metal particles and electronegative nitrogen of PANI. The quantum dot-sensitized solar cell (QDSSC) with the FTO/Cu-P heterostructure CE exhibited a higher energy conversion efficiency (4.12%) than those with Pt (1.85%), Cu₂S (3.71%), PANI (0.77%), and PANI-Cu₂S (P-Cu) (1.01%) CEs.