CHAPTER 4. Tandem Photoelectrochemical Cells for Water Splitting

In this chapter the motivation and theoretical framework for using tandem cells to achieve overall solar-to-hydrogen energy conversion are first examined. The many different systems that have been investigated using various combinations of photovoltaic cells and photoelectrodes are critically reviewed. In order to be economically competitive with simple “brute force” strategies or the production of H2 from fossil fuels, a practical water splitting tandem cell must optimize cost, longevity and performance. A promising approach that meets these requirements is the combination of a stable photoanode material (oxide semiconductor) in tandem with an inexpensive PV cell like the dye sensitized solar cell (DSSC). State-of-the-art solar-to-hydrogen efficiencies in the 2–3% range can be already obtained with this approach in real devices, but much more research is needed to realize a simple tandem device with an efficiency > 10%. Future research needs are finally outlined.