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ZnO-Cu2O core-shell nanowires as stable and fast response photodetectors
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0002-7893-7405
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0001-7949-0935
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0001-7475-6394
Division of Surface and Corrosion Science, KTH Royal Institute of Technolog.
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2018 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 51, p. 308-316Article in journal (Refereed) Published
Abstract [en]

In this work, we present all-oxide p-n junction core-shell nanowires (NWs) as fast and stable self-powered photodetectors. Hydrothermally grown n-type ZnO NWs were conformal covered by different thicknesses (up to 420 nm) of p-type copper oxide layers through metalorganic chemical vapor deposition (MOCVD). The ZnO NWs exhibit a single crystalline Wurtzite structure, preferentially grown along the [002] direction, and energy gap Eg=3.24 eV. Depending on the deposition temperature, the copper oxide shell exhibits either a crystalline cubic structure of pure Cu2O phase (MOCVD at 250 °C) or a cubic structure of Cu2O with the presence of CuO phase impurities (MOCVD at 300 °C), with energy gap of 2.48 eV. The electrical measurements indicate the formation of a p-n junction after the deposition of the copper oxide layer. The core-shell photodetectors present a photoresponsivity at 0 V bias voltage up to 7.7 µA/W and time response ≤0.09 s, the fastest ever reported for oxide photodetectors in the visible range, and among the fastest including photodetectors with response limited to the UV region. The bare ZnO NWs have slow photoresponsivity, without recovery after the end of photo-stimulation. The fast time response for the core-shell structures is due to the presence of the p-n junctions, which enables fast exciton separation and charge extraction. Additionally, the suitable electronic structure of the ZnO-Cu2O heterojunction enables self-powering of the device at 0 V bias voltage. These results represent a significant advancement in the development of low-cost, high efficiency and self-powered photodetectors, highlighting the need of fine tuning the morphology, composition and electronic properties of p-n junctions to maximize device performances.

Place, publisher, year, edition, pages
Elsevier, 2018. Vol. 51, p. 308-316
National Category
Other Physics Topics
Research subject
Experimental Physics
Identifiers
URN: urn:nbn:se:ltu:diva-69838DOI: 10.1016/j.nanoen.2018.06.058ISI: 000440682100034Scopus ID: 2-s2.0-85049324019OAI: oai:DiVA.org:ltu-69838DiVA, id: diva2:1223184
Note

Validerad;2018;Nivå 2;2018-08-02 (rokbeg)

Available from: 2018-06-25 Created: 2018-06-25 Last updated: 2019-04-19Bibliographically approved
In thesis
1. Advanced Nanostructured Transition Metal Oxide Semiconductors for Solar Energy Applications
Open this publication in new window or tab >>Advanced Nanostructured Transition Metal Oxide Semiconductors for Solar Energy Applications
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Avanceradenanostrukturerade halvledare av övergångsmetalloxid för solenergiapplikationer
Abstract [en]

Increasing energy consumption and its environmental impacts make it necessary to look for alternative energy sources. Solar energy as huge energy source that can cover the terms sustainability is considered as a favorable alternative. Optoelectronic devices like solar cells and photoelectrochemical cells are in very high interest to provide the energy that we need. They can convert solar energy, as a sustainable energy source, to electricity and fuel. Transition metal oxides (TMOs) due to high chemical stability, abundance, facile production and low cost are favorable materials to be used in these optoelectronic applications. In TMOs, d orbitals electrons contribute in forming bonds that gives special magnetic, electronic and geometric characteristics to these materials. They can be synthesized with different types of chemical and physical deposition methods.

The electronic properties of TMOs varies from metallic characteristics to electrical insulators. Transition metal oxide semiconductors (TMOSs) are mostly used in optoelectronic devices. Tuning the properties of TMOSs like, composition, morphology, dimensions, crystal structure, improves the performance of the optoelectronic devices. The light absorption, charge carrier mobility, the time scale between charge injection, regeneration and recombination processes are some of the properties critical to exploitation of TMOSs in solar cells and solar fuel technology.

In this thesis, we explore the use of nanostructured TMOSs in all-oxide solar cells, photodetectors and photoelectrochemical cells. 1-dimentional heterojunctions of n-type transparent semi-conductive metal oxides (ZnO and TiO2) in conjunction to p-type light absorbing semi-conductive metal oxides (Cu2O and Co3O4) have been tested in all-oxide photodetectors and solar cells.  It is shown that the 1-dimentional nanostructured geometry (nanowires, nanotubes) improves the charge separation and charge transport properties. Increasing the surface to volume aspect ratio in nanowires and nanotubes improves the light absorption compare to the thin film geometry. Our ZnO-Cu2O core-shell nanowire photodetector is the fastest visible light photodetector reported till now. Mesoporous NiO photocathode, sensitized with a biomimetic FeFe-catalyst and coumarin C343 dye, was tested in a photoelectrochemical cell for hydrogen production. This system is the first solar fuel device based on a biomimetic FeFe-catalyst and it shows a Faradic efficiency of 50% in hydrogen production. Cobalt catalysts have higher Faradic efficiency but their performance due to hydrolysis in low pH condition is limited. Nanostructured hematite/magnetite film as a photoanode was tested in a photoelectrochemical cell for water splitting. This hybrid electrode improved the photoactivity of the photoelectrochemical cell for water splitting. The main mechanism for the improvement of the functional properties relies with the role of the magnetite phase, which improves the charge carrier mobility of the composite system, compared to pure hematite, which acts as good light absorbing semiconductor.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
Metal Oxide, Photovoltaic, Semiconductors, Self-powered photodetectors, Photoelectrochemical cell, Solar fuel, Water splitting
National Category
Materials Engineering
Research subject
Experimental Physics
Identifiers
urn:nbn:se:ltu:diva-73709 (URN)978-91-7790-366-6 (ISBN)978-91-7790-367-3 (ISBN)
Public defence
2019-06-14, E632, Luleå University of Technology, Luleå, 10:00 (English)
Opponent
Supervisors
Funder
Vinnova, 224320
Available from: 2019-04-23 Created: 2019-04-19 Last updated: 2019-05-22Bibliographically approved

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Ghamgosar, PedramRigoni, FedericaYou, ShujieGilzad Kohan, MojtabaConcina, IsabellaAlmqvist, NilsVomiero, Alberto

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