Multijunction Si photocathodes with tunable photovoltages from 2.0 V to 2.8 V for light induced water splitting

Urbain, Félix; Smirnov, Vladimir; Becker, Jan‐Philipp; Lambertz, Andreas; Yang, F.; Ziegler, Jürgen; Kaiser, Bernhard; Jaegermann, Wolfram; Rau, Uwe; Finger, F.

doi:10.1039/c5ee02393a

Cited by 187 publications

(177 citation statements)

References 48 publications

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“…The obtained results can then be applied to further optimize devices based on multijunction solar cells. [2][3][4][5][6] Especially in the last few years, there have been a lot of great accomplishments in this direction. McDowell and Hu 7,8 investigated the performance of n-Si | TiO 2 heterojunctions and TiO 2 covered np + homojunctions with an additional Ni catalyst, achieving good long term stability.…”

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confidence: 99%

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The Impact of Different Si Surface Terminations in the (001) n-Si/NiOx Heterojunction on the Oxygen Evolution Reaction (OER) by XPS and Electrochemical Methods

Tengeler

Fingerle

Calvet

et al. 2018

J. Electrochem. Soc.

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The interaction between (001) n-Si and NiO x was investigated with regard to the oxygen evolution reaction (OER), applicable either for water splitting or CO 2 reduction. Thin layers of nickel oxide were deposited step by step by reactive sputter deposition and analyzed in-situ after each step using X-ray photoelectron spectroscopy (XPS). This was performed for silicon with different surface preparations: H-termination, thermally grown oxide (2 Å) and a monolayer of native oxide (4 Å). Upon contact formation the initial flatband like situation in the Si substrates changed to a 0.35 to 0.4 eV upward band bending for all three heterojunctions, with an alignment of the valence bands favorable to hole extraction. With near identical heterojunction performance and identical NiO x catalyst layers (η(10 mA/cm 2 ) = 0.44 ± 0.01 V vs. RHE on Ni) an equally identical performance for the OER would be expected. While the native oxide covered sample shows the expected performance in cyclic voltammetry measurements the others fall short of expectations. Using chopped light measurements, this under-performance could be attributed to a higher density of defect states at the silicon surface. Apparently a 4Å SiO 2 layer is sufficient protection to prevent the formation of defect states during NiO x deposition, thinner protective layers or none at all result in increased defect states, while thicker layers perform poorly due to their high resistance. Direct photoelectrochemical devices are an exciting approach to the storage of renewable energies. Depending on the preferred energy cycle they can be used either for water splitting or CO 2 reduction, in the end it is only a question of the employed catalysts and necessary overpotentials. A direct photoelectrochemical device has two main functional parts, which do not necessarily have to be physically separate. First, there is the photoabsorber, basically a solar cell, who has to supply the necessary photovolage U ph and photocurrent J ph to power the desired redox reaction. Second, the catalytic surface, which is in direct contact with the electrolyte and should be catalytically active, thus allowing high current densities at low overpotentials η. In an ideal case the total device performance should be a result of those two contributions only.Initial research on water splitting was focused on a single semiconducting material performing well in both functions. This was first demonstrated on a TiO 2 electrode by Fujishima and Honda in 1972. 1 In such a device the photoabsorber functionality is defined by the interface junction between semiconductor and electrolyte. Investigated materials were mostly wide bandgap materials, as they could, in theory, provide the necessary U ph .However, the double function of the semiconductor electrolyte interface makes an evaluation of such devices difficult, as it is hard to determine whether a lack of performance is a result from poor current voltage (IE) behavior of the junction or the poor catalytic performance of the material. Furthermore, t...

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confidence: 99%

“…The obtained results can then be applied to further optimize devices based on multijunction solar cells. [2][3][4][5][6] …”

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confidence: 99%

The Impact of Different Si Surface Terminations in the (001) n-Si/NiOx Heterojunction on the Oxygen Evolution Reaction (OER) by XPS and Electrochemical Methods

Tengeler

Fingerle

Calvet

et al. 2018

J. Electrochem. Soc.

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“…The development of the tandem , triple , and quadruple junction solar cells used in this is study is described elsewhere. The solar cells were particularly developed according to the requirements for the application as photocathodes in a solar water splitting device.…”

Section: Methodsmentioning

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Modeling and practical realization of thin film silicon‐based integrated solar water splitting devices

Becker

Urbain

Smirnov

et al. 2016

Physica Status Solidi (a)

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An integrated solar water splitting device based on thin film silicon multijunction photocathodes is presented. A graphical representation of the photovoltaic current–voltage data is introduced which allows for an estimation of the maximum achievable solar‐to‐hydrogen efficiency of the integrated device. Furthermore, a simple yet very useful series circuit model is used to predict the photoelectrochemical performance of the integrated device in a more elaborate way when the j–V characteristics of the individual components are known. Within the model, the j–V characteristics of each component can be either modeled with parameters from the literature or measured. The photocathode, the electrolyte concentration, and the hydrogen and oxygen evolving catalysts were varied exemplarily and the impact of each component on the integrated device performance was evaluated. A maximum solar‐to‐hydrogen efficiency of 9.5% was found using a triple junction solar cell functionalized with a Pt catalyst for the hydrogen evolution and a RuO2 catalyst for the oxygen evolution reaction in a 1 M KOH electrolyte. This result was confirmed experimentally and is compared to efficiencies reported in the literature.

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“…Using light concentration Fujii et al showed >12% on a large area including a membrane for product separation [27]. catalysts [28]. Stellmach et al have reached 2.5% with the noble metal free HER catalyst MoS 2 catalyst in a complete wireless 'artificial leaf' configuration [29].…”

Section: Group (Ii A) 'Back-back-multi'mentioning

confidence: 98%

Architectures for scalable integrated photo driven catalytic devices-A concept study

Kirner

Bogdanoff

Stannowski

et al. 2016

International Journal of Hydrogen Energy

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Multijunction Si photocathodes with tunable photovoltages from 2.0 V to 2.8 V for light induced water splitting

Cited by 187 publications

References 48 publications

The Impact of Different Si Surface Terminations in the (001) n-Si/NiOx Heterojunction on the Oxygen Evolution Reaction (OER) by XPS and Electrochemical Methods

The Impact of Different Si Surface Terminations in the (001) n-Si/NiOx Heterojunction on the Oxygen Evolution Reaction (OER) by XPS and Electrochemical Methods

Modeling and practical realization of thin film silicon‐based integrated solar water splitting devices

Architectures for scalable integrated photo driven catalytic devices-A concept study

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