One-Step Electrochemical Deposition of Hierarchical CuS Nanostructures on Conductive Substrates as Robust, High-Performance Counter Electrodes for Quantum-Dot-Sensitized Solar Cells

An ideal counter electrode, with high electrocatalytic activity, high performance stability, and applicable fabrication simplicity, is essential to give full play to the advantages of quantum-dot-sensitized solar cells (QDSSCs) such as high theoretical efficiency and simple synthetic procedure. Herein, we report a facile one-step electrochemical deposition approach for the growth of hierarchical covellite (CuS) nanostructures on conductive glass substrates. The as-synthesized copper sulfide can be employed directly as a robust, low-cost, and high-efficiency counter electrode without any post-treatments for QDSSCs filled with aqueous sulfide/polysulfide (S2–/Sn2–) electrolyte. The morphology and structure of the well-crystalline, strongly substrate-adhesive hierarchical CuS nanostructured film have been studied by X-ray and electron-based characterizations. QDSSC using this newly synthesized CuS as counter electrode achieves a higher power conversion efficiency of 4.32% than the one applying cuprous sulfide (Cu2S) on brass substrate (4.08%) or platinum counter electrode (2.85%). Furthermore, this CuS counter electrode shows a high and consistent electrocatalytic activity toward polysulfide reduction confirmed by the electrochemical measurements, destining the improved photovoltaic performance and superior stability of the corresponding QDSSC device.