Novel Micropixelation Strategy to Stabilize Semiconductor Photoelectrodes for Solar Water Splitting Systems

We demonstrate a novel micropixelation strategy to stabilize the p-i hydrogenated amorphous silicon (a-Si:H) photocathodes used for hydrogen production in photoelectrochemical water splitting. The main mechanism of corrosion of planar electrodes involves reduction of the underlying SnO ₂ contact layer by electrolyte that penetrates through pinholes in the a-Si:H. We photolithographically isolate square pixels (100 μm × 100 μm) of a-Si:H by etching narrow channels in the a-Si:H and filling with protective a-SiN _x. Under illumination and bias, we observe improved durability of the micropixelated photocathodes compared to planar electrodes. Extended dark potentiostatic testing also exhibits this slowing and isolation of corrosion by the micropixelated electrode. Implementation of this micropixelation strategy is a key toward creating a water-splitting system based on micrometer-scale Si p-n junction pixels. Panels of these corrosion-resistant pixels could be connected in series to produce photovoltages sufficient to split-water while avoiding photocorrosion. Micropixelation could also improve stability in other photoelectrochemical solar fuel production systems.