Silicon
photovoltaic cells functionalized with water-splitting
electrocatalysts are promising
candidates for unassisted water splitting. In these devices, the total
surface of silicon solar cells is covered with electrocatalysts, causing
issues with (i) stabilizing silicon solar cells in water and (ii)
device efficiency due to parasitic optical absorption in electrocatalysts.
We describe and validate a water-splitting device concept using a
crystalline silicon solar cell where the front side is covered with
an insulating Si3N5 antireflection coating.
The Ag contacts, fired through the antireflection coating, are removed
and subsequently substituted with NiFe layered double hydroxide (LDH)
or Cu/NiFe-LDH electrocatalysts. In this device, only the site of
Ag contacts, nearly 2% of the total device area, is covered by the
electrocatalyst. We found that this small area of the catalyst does
not limit device performance and the addition of a Cu interlayer between
Si and NiFe-LDH improves device performance and stability. The unassisted
water-splitting efficiency of 11.31%, measured without separating
the evolved gases, is achieved using a device composed of three series-connected
silicon solar cells and an NiFe-LDH/Cu/Ni-foam counter electrode in
a highly alkaline electrolyte.
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