1 research outputs found
Solution-Deposited F:SnO<sub>2</sub>/TiO<sub>2</sub> as a Base-Stable Protective Layer and Antireflective Coating for Microtextured Buried-Junction H<sub>2</sub>‑evolving Si Photocathodes
Protecting Si photocathodes from
corrosion is important for developing tandem water-splitting devices
operating in basic media. We show that textured commercial Si-pn<sup>+</sup> photovoltaics protected by solution-processed semiconducting/conducting
oxides (plausibly suitable for scalable manufacturing) and coupled
to thin layers of Ir yield high-performance H<sub>2</sub>-evolving
photocathodes in base. They also serve as excellent test structures
to understand corrosion mechanisms and optimize interfacial electrical
contacts between various functional layers. Solution-deposited TiO<sub>2</sub> protects Si-pn<sup>+</sup> junctions from corrosion for ∼24
h in base, whereas junctions protected by F:SnO<sub>2</sub> fail after
only 1 h of electrochemical cycling. Interface layers consisting of
Ti metal and/or the highly doped F:SnO<sub>2</sub> between the Si
and TiO<sub>2</sub> reduce Si-emitter/oxide/catalyst contact resistance
and thus increase fill factor and efficiency. Controlling the oxide
thickness led to record photocurrents near 35 mA cm<sup>–2</sup> at 0 V vs RHE and photocathode efficiencies up to 10.9% in the best
cells. Degradation, however, was not completely suppressed. We demonstrate
that performance degrades by two mechanisms, (1) deposition of impurities
onto the thin catalyst layers, even from high-purity base, and (2)
catastrophic failure via pinholes in the oxide layers after several
days of operation. These results provide insight into the design of
hydrogen-evolving photoelectrodes in basic conditions, and highlight
challenges