Proceedings of MATSUS Fall 2023 Conference (MATSUSFall23)
DOI: https://doi.org/10.29363/nanoge.matsus.2023.200
Publication date: 18th July 2023
Photovoltaic-coupled photoelectrochemical (PV-PEC) water splitting devices offer a route to high efficiency solar-to-hydrogen (STH) conversion with low-cost and non-toxic materials, in particular given the recent advances in efficient and earth-abundant PEC (e.g. metal-oxide) and PV (e.g. organic, perovskite) materials. [1][2][3] However, achieving STH efficiencies relevant for commercialisation (~15-20%) requires careful optimisation of the electronic and optical properties of the constituent materials, as well of the device configuration to minimise parasitic optical and electrical losses.
Here, we present a optical-electronic model for simulating the current-voltage curves of PV-PEC tandem cells, and which includes descriptions of important (optical and electronic) loss mechanisms. PV operation is modelled using diode equations that incorporate loss estimates due to radiative and non-radiative recombination. For describing PEC operation, we extend the Gärtner formulism for PEC photocurrent generation to treat surface recombination due to charge trapping and correct for Fermi level pinning due to an overpotential drop over the Helmholtz layer. We then study the effect of changing semiconductor properties, including conduction and valence band levels, electron and hole masses, charge-diffusion length, Fermi level and trap densities, as well as optical considerations (e.g. parasitic light absorption due to electrolyte and bubble formation) on PV-PEC operation. This allows us to determine the PEC and PV semiconductor properties and device configurations that are required to reach STH efficiencies relevant for commercialisation, in particular using state-of-the-art metal-oxide, organic and perovskite semiconductors.