Examining architectures of photoanode–photovoltaic tandem cells for solar water splitting

Abstract

Given the limitations of the materials available for photoelectrochemical water splitting, a multiphoton (tandem) approach is required to convert solar energy into hydrogen efficiently and durably. Here we investigate a promising system consisting of a hematite photoanode in combination with dye-sensitized solar cells with newly developed organic dyes, such as the squaraine dye, which permit new configurations of this tandem system. Three configurations were investigated: two side-by-side dye cells behind a semitransparent hematite photoanode, two semitransparent dye sensitized solar cells (DSCs) in front of the hematite, and a trilevel hematite/DSC/DSC architecture. Based on the current-voltage curves of state-of-the-art devices made in our laboratories, we found the trilevel tandem architecture (hematite/SQ1 dye/N749 dye) produces the highest operating current density and thus the highest expected solar-to-hydrogen efficiency (1.36% compared with 1.16% with the standard back DSC case and 0.76% for the front DSC case). Further investigation into the wavelength-dependent quantum efficiency of each component revealed that in each case photons lost as a result of scattering and reflection reduce the performance from the expected 3.3% based on the nanostructured hematite photoanodes. We further suggest avenues for the improvement of each configuration from both the DSC and the photoanode parts.

Efficient photoelectrochemical hydrogen production from bismuth vanadate-decorated tungsten trioxide helix nanostructures

“…In fact, our samples with the 5.5-mm thickness have weak transparency; hence, we did not consider using it in a photoanode/photovoltaic tandem cell. However, there is the previous report mentioned the photovoltaic/photoanode tandem cell in which the photovoltaic (such as a dye-sensitized solar cell (DSSC)) is placed in front of the photoanode 29 . Although the performance is not best compared with other kinds of configurations, it still shows potential application in the future.…”

Activation of Hematite Nanorod Arrays for Photoelectrochemical Water Splitting

“…This would limit the use of tandem architectures to provide the extra potential required by hematite for the hydrogen evolution reaction. [32] At 600 °C/5 minutes, the long wavelength transmission is nearly identical to that of an uncoated FTO substrate. While the transparency is somewhat attenuated with increased time, >80% average transmission in this region is retained even after 8 hours.…”

Electrochemical and photoelectrochemical investigation of water oxidation with hematite electrodes

“…[6][7][8] While hematite's conduction band is too low to reduce water, application of an external bias through a photovoltaic device, or integration of a small bandgap water reduction system in a tandem configuration, would overcome this drawback. [9][10][11] Despite these favorable characteristics, the water oxidation efficiency at hematite electrodes has been too poor to be commercially viable. One problem is the combination of a relatively long visible light penetration depth of 375 nm (for 550 nm light), 3 combined with a very short minority carrier lifetime and mobility, which hinders efficient separation and collection.…”