Interface architecture of low-cost and stable three-dimensional composite counter electrodes for QDSCs

Abstract

In this work, a series of low-cost, stable, and highly efficient composite counter electrodes (CEs) in three-dimensional (3D) structure have been designed with multi-wall carbon nanotubes (MWCNTs) as the framework for carrier transport and nanographite or CuS nanoparticles loaded on carbon tubes as catalytic active sites. CuS nanoparticles are synthesized by loading on acid-treated MWCNTs in various routes to optimize the 3D CE interface and microstructure. The photovoltaic properties, including stability, are investigated and compared within Pt, MWCNT, nanographite/MWCNT, and CuS/MWCNT CEs based on the characterization (SEM, TEM, XRD, EELS, and IR spectrum), electrochemical impedance spectroscopy (EIS), Tafel curve, incident photon-to-current conversion efficiency (IPCE), and optical current density–voltage curve under one sun. The result shows that one-step synthesized CuS/acid-treated MWCNT CE overcomes all other electrodes on both the photovoltaic property and stability in QDSCs at identical conditions and is a potential candidate for commercial CEs of solar cells for mass production.