Thin films from copper sulfide (CuxS) are the most commonly used electrocatalyst
counter electrodes (CEs) for high-efficiency quantum dot sensitized solar cells
(QDSSCs) because of its superior electrocatalytic activity in the presence of polysul-
fide electrolytes. In addition to the stability issues, the CuxS CEs are usually prepared
by complicated, costly, time consuming, and less productive methods, which are
inadequate for practical applications of QDSSCs. In this work, we present a simple
approach for fabricating an efficient and stable CE for QDSSCs using pure covellite
phase CuS nanoparticles (NPs) pre-prepared via a cheap, fast, and scalable chemical
method. The catalyst ink was obtained by mixing the as-prepared CuS NPs with polyvinylidene
fluoride, as a polymeric binder, which was then directly applied to a conductive
fluorine-doped tin oxide substrate without any further high temperature post
treatment. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS),
and Tafel polarization measurements were used to investigate the electrocatalytic
activity of the CuS NPs CE. The power conversion efficiency of 2.6% was achieved
from CdS QDSSC assembled with CuS NPs CE, which was higher than 1.57% for
conventional Cu2S/brass and 1.33% for Pt CEs under one-sun illumination. The CdS
QDSSC with CuS NPs CE was also able to supply a constant photocurrent value
without any obvious decrease under light soaking test, in contrast to the devices with
Cu2S/brass and Pt CEs, which showed inferior stability. This remarkable photovoltaic
performance was attributed to the nanoporous morphology and the excellent
electrocatalytic activity of CuS NPs CE. |
