Solar-to-hydrogen efficiency

These early tests were not conducted with the most efficient solar cells available at that time. The record efficiency then was about 30% for a laboratory cell (see Fig. 4) and those cells were not easily obtainable. Today s record efficiency is 40.7%, and 35% efficient cells are commercially available.18 Therefore, 40% solar to hydrogen efficiency is expected in the near term assuming a heat boost of 40%, a multijunction solar cell efficiency of 35%, and an optical efficiency of 85%. A 40% multijunction solar cell would yield a solar to hydrogen conversion efficiency of almost 50%. Nevertheless, electrochemical theoretical results calculated by Licht, shown in Figure 10, are consistent with these predictions based on Solar Systems early experiments.15... 

In the general case, where an external bias voltage may provide additional energy for the production of hydrogen, the solar-to-hydrogen efficiency may be defined by (Bolton, 1996)... 

Solar-to-hydrogen efficiency. Photocurrent efficiency obtained under zero-bias conditions and using AM 1.5 G light spectrum. 

The energy conversion efficiency is one of the key performance indicators of the PEC cell. Assuming that all the photogenerated electrons and holes are used for the water splitting reaction, the overall solar-to-hydrogen efficiency is given by... 

A more direct method to determine the solar-to-hydrogen efficiency is to measure the amount of evolved hydrogen by mass spectrometry, gas chromatography [73, 74], or by following the water displacement in an inverted burette. The STH efficiency for this approach is given by... 

Zhu, E., Hu, J., Kunrath, A., Matulionis, I., Marsen, B., Cole, B., Miller, E.L., Madan, A. a-SiC H films used as photoelectrodes in a hybrid, thin-film silicon photoelectrochemical (PEC) Cell for progress toward 10% solar-to hydrogen efficiency. Sol. Hydrogen Nanotechnol. Proc. SPIE 6650, 66500S (2007)... 

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