Facile fabrication of highly efficient carbon nanotube thin film replacing CuS counter electrode with enhanced photovoltaic performance in quantum dot-sensitized solar cells

• Facile fabrication of CNT electrode and used as highly efficient CE for QDSSC.
• CNT exhibits excellent electrocatalytic activity than CuS and Pt for S2−/Sn2−S2−/Sn2− redox couple.
• The η of QDSSC with CNT CE (4.67%) is higher than CuS (3.67%) and Pt (1.56%).
• The CNT CE shows excellent stability in photoelectric performance.

An ideal counter electrode (CE), with high electrocatalytic activity, high performance stability, cost-efficient and applicable fabrication simplicity, is necessary to give full play to the advantages of quantum dot-sensitized solar cells (QDSSCs). Herein, we report a facile one-step preparation for carbon nanotubes (CNTs) have been explored as an electrocatalyst and low-cost alternative to platinum (Pt) and cuprous sulfide (CuS) CEs for polysulfide reduction in QDSSCs. QDSSC using this newly prepared CNT as a CE achieves a higher power conversion efficiency of 4.67% than those with a CuS (3.67%) or Pt CE (1.56%). Besides, a preliminary stability test reveals that the new CNT CE exhibits good stability. The results of Tafel polarization and electrochemical impedance spectroscopy measurements revealed that the CNTs had higher electrocatalytic activity for the polysulfide redox reaction and a smaller charge transfer resistance (8.61 Ω) at the CE/electrolyte interface than the CuS (21.87 Ω) and Pt (54.99 Ω) CEs. These results indicate that the CNT CE has superior electrocatalytic activity and can potentially replace CuS and Pt as CEs in QDSSCs. The preparation method of the CNT CE is simple and shows much promise as an efficient, stable, cost-effective and environmentally friendly CE for QDSSCs.

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