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CuInxGa1-xSe2 as an efficient photocathode for solar hydrogen generation
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
2013 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 38, no 35, 15027-15035 p.Article in journal (Refereed) Published
Abstract [en]

Utilizing the energy in the sun to efficiently split water into hydrogen and oxygen can have a huge beneficial impact on a future post-carbon energy system. There is still, however, some way to go before this concept will be fully competitive. At the heart of the problem is finding and designing materials that can drive the photoreaction in an efficient and stable way. In this work we demonstrate how CIGS (CuInxGa1-xSe2), can be used for photo reduction of water into hydrogen. CIGS, which is a proven good solar cell material, does not in itself have the appropriate energetics to drive the reaction to any larger extent. Here we show that by utilizing a solid state pn-junction for charge separation and a catalyst deposited on the surface, the efficiency is significantly improved and photocurrents of 6 mA/cm(2) are demonstrated for the reduction reaction in the configuration of a photo-electrochemical cell. The stability of CIGS in water under illumination turns out to be a problem. In our present set-up, we demonstrate that separation between the charge carrier generation, which takes place in the solar cell, from the catalysis, which takes place in the electrolyte leads to improved stability, while keeping the essential functions of the processes. By incorporating appropriate charge separation layers and optimizing the catalytic conditions at the surface of the electrodes, photocurrents in excess of 20 mA/cm2 are reached for the reduction half reaction, demonstrating how essentially the full potential of GIGS as an efficient absorber material can be utilized in photocatalytic reduction of water into hydrogen.

Place, publisher, year, edition, pages
2013. Vol. 38, no 35, 15027-15035 p.
Keyword [en]
Solar water splitting, Hydrogen production, CIGS, CuInGaSe2, PEC, Water electrolysis
National Category
Natural Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Electronics
Identifiers
URN: urn:nbn:se:uu:diva-214041DOI: 10.1016/j.ijhydene.2013.09.094ISI: 000328006500010OAI: oai:DiVA.org:uu-214041DiVA: diva2:684078
Available from: 2014-01-07 Created: 2014-01-07 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Highly Efficient CIGS Based Devices for Solar Hydrogen Production and Size Dependent Properties of ZnO Quantum Dots
Open this publication in new window or tab >>Highly Efficient CIGS Based Devices for Solar Hydrogen Production and Size Dependent Properties of ZnO Quantum Dots
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Materials and device concepts for renewable solar hydrogen production, and size dependent properties of ZnO quantum dots are the two main themes of this thesis.

ZnO particles with diameters less than 10 nm, which are small enough for electronic quantum confinement, were synthesized by hydrolysis in alkaline zinc acetate solutions. Properties investigated include: the band gap - particle size relation, phonon quantum confinement, visible and UV-fluorescence as well as photocatalytic performance. In order to determine the absolute energetic position of the band edges and the position of trap levels involved in the visible fluorescence, methods based on combining linear sweep voltammetry and optical measurements were developed.

The large band gap of ZnO prevents absorption of visible light, and in order to construct devices capable of utilizing a larger part of the solar spectrum, other materials were also investigated, like hematite , Fe2O3, and CIGS, CuIn1-xGaxSe2.

The optical properties of hematite were investigated as a function of film thickness on films deposited by ALD. For films thinner than 20 nm, a blue shift was observed for both the absorption maximum, the indirect band gap as well as for the direct transitions. The probability for the indirect transition decreased substantially for thinner films due to a suppressed photon/phonon coupling. These effects decrease the visible absorption for films thin enough for effective charge transport in photocatalytic applications.

CIGS was demonstrated to be a highly interesting material for solar hydrogen production. CIGS based photocathodes demonstrated high photocurrents for the hydrogen evolution half reaction. The electrode stability was problematic, but was solved by introducing a modular approach based on spatial separation of the basic functionalities in the device. To construct devices capable of driving the full reaction, the possibility to use cells interconnected in series as an alternative to tandem devices were investigated. A stable, monolithic device based on three CIGS cells interconnected in series, reaching beyond 10 % STH-efficiency, was finally demonstrated. With experimental support from the CIGS-devices, the entire process of solar hydrogen production was reviewed with respect to the underlying physical processes, with special focus on the similarities and differences between various device concepts.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 155 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1134
Keyword
ZnO, Nanoparticles, Quanum Dots, Size Dependent Properties, Hematite, CIGS, Solar Water Splitting, Hydrogen Production, PEC, Photoelectrochemical cells, PV-electrolysis
National Category
Inorganic Chemistry Physical Chemistry Materials Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-221260 (URN)978-91-554-8918-2 (ISBN)
Public defence
2014-05-23, Häggsalen, Ångström Laboratory, Lägehydsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2014-04-24 Created: 2014-03-27 Last updated: 2014-05-27Bibliographically approved

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Jacobsson, Jesper T.Platzer-Björkman, CharlotteEdoff, MarikaEdvinsson, Tomas

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