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

Abstract

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.

Silicon Thin Films: Functional Materials for Energy, Healthcare, and IT Applications

“…The theoretical, ideal operation point of a light induced water splitting device is indicated at E thermo. = 1.23 V. Including the electrode overpotentials, the voltage at the operation point must be in the range of 1.5–2 V. Adapted with permission …”

“…The operating voltage (0 V) for unbiased solar driven water splitting is indicated. Adapted with permission …”

Nanostructured p-Type Semiconductor Electrodes and Photoelectrochemistry of Their Reduction Processes

“…Since H 2 is attainable as the reduction product of H + cation it is then mandatory to focus the attention towards p-type electrodes having photoelectrocatalytic properties [62][63][64] towards the reduction of the proton either in the pristine state or with the surface modified by a dye-absorber/photocatalytic agent [65,66]. A comprehensive list of p-type semiconductor cathodes for the photoelectrochemical production of H 2 has been given recently in [67] when the design of optimized photoelectrochemical water splitting cells [68,69] was considered, and solar radiation represented the primary energy source for the activation of this conversion device [70]. One of the main concerns at the basis of the development of PECs for water splitting [71] which produce molecular H 2 at the (photo)cathode and O 2 at the (photo)anode is the replacement of precious metals like Pt or Ru photoelectrocatalysts with durable semiconducting electrodes of p-type based on cheaper metal oxides, phosphides and sulfides/disulfides or Si, in order to photoactivate HER (hydrogen evolution reaction).…”

“…A comprehensive list of p-type semiconductor cathodes for the photoelectrochemical production of H2 has been given recently in [67] when the design of optimized photoelectrochemical water splitting cells [68,69] was considered, and solar radiation represented the primary energy source for the activation of this conversion device [70]. One of the main concerns at the basis of the development of PECs for water splitting [71] The Ru-complex O22 immobilized on NiO surface is the dye-sensitizer acting as an electron donor towards the co-catalyst CodmgBF2, and as an electron acceptor from NiO.…”

The Influence of Operation Temperature and Variations of the Illumination on the Performance of Integrated Photoelectrochemical Water‐Splitting Devices

“…To predict the PV‐EC behavior and the STH efficiency under varying conditions, an electrical series connection model of the integrated device was used that combines the J‐V characteristics of the individual components . Here, the measured J‐V curves of the a‐Si : H/a‐Si : H/μc‐Si : H cell under varying conditions were combined with the measured respective linear sweep voltammetry (LSV) curves of the different catalyst systems.…”