Cobalt silicide was used as a counter electrode in order to confirm its reliability in dye-sensitized solar
cell (DSSC) devices. 100 nm-Co/300 nm-Si/quartz was formed by an evaporator and cobalt silicide was formed by
vacuum heat treatment at 700℃ for 60 min to form approximately 350 nm-CoSi. This process was followed by
etching in 80℃-30% H2SO4 to remove the cobalt residue on the cobalt silicide surface. Also, for the comparison
against Pt, we prepared a 100 nm-Pt/glass counter electrode. Cobalt silicide was used for the counter electrode in
order to confirm its reliability in DSSC devices and maintained for 0, 168, 336, 504, 672, and 840 hours at 80℃.
The photovoltaic properties of the DSSCs employing cobalt silicide were confirmed by using a simulator and
potentiostat. Cyclic-voltammetry, field emission scanning electron microscopy, focused ion beam scanning electron
microscopy, and energy dispersive spectrometry analyses were used to confirm the catalytic activity, microstructure,
and composition, respectively. The energy conversion efficiency (ECE) as a function of time and ECE of the DSSC
with Pt and CoSi counter electrodes were maintained for 504 hours. However, after 672 hours, the ECEs decreased
to a half of their initial values. The results of the catalytic activity analysis showed that the catalytic activities of
the Pt and CoSi counter electrodes decreased to 64% and 57% of their initial values, respectively(after 840 hours).
The microstructure analysis showed that the CoSi layer improved the durability in the electrolyte, but because the
stress concentrates on the contact surface between the lower quartz substrate and the CoSi layer, cracks are formed
locally and flaking occurs. Thus, deterioration occurs due to the residual stress built up during the silicidation of the
CoSi counter electrode, so it is necessary to take measures against these residual stresses, in order to ensure the
reliability of the electrode.