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High-efficiency water splitting systems

: May, Matthias M.; Döscher, Henning; Turner, John A.


Sharp, Ian D. (Ed.):
Integrated solar fuel generators
Cambridge: RSC, 2019 (RSC energy and environment series 22)
ISBN: 978-1-78262-555-1
ISBN: 978-1-78801-031-3
ISBN: 978-1-78801-521-9
Aufsatz in Buch
Fraunhofer ISI ()

In this chapter, we discuss the prerequisites for high-efficiency water splitting and their implementation with tandem cells based on absorbers of the III-V semiconductor material class. A brief outline of efficiency-limiting factors shows that at a given set of boundary conditions, such as catalyst performance, the optimum tandem absorbers require a very precise control of opto-electronic properties, as facilitated by the III-V compounds. After a short history of high efficiency solar energy conversion, we present recent implementations of highly efficient water splitting systems with solar-to-hydrogen efficiencies of 14-16% together with an outlook on further improvements. Even if other absorber systems turn out to be more cost-competitive, the III-V systems currently serve as a testbed for high-efficiency water splitting in general, with lessons to be learned for catalyst requirements, cell design, and efficiency validation. We conclude with a discussion of appropriate efficiency benchmarking routines, outlining potential pitfalls for multi-junction absorbers and how to avoid them.