Logo: to the web site of Uppsala University

uu.sePublications from Uppsala University
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Reactive sputtering of Cu2ZnSnS4 thin films - Target effects on the deposition process stability
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, Technology, Department of Engineering Sciences, Solid State Electronics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
Show others and affiliations
2014 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 240, p. 281-285Article in journal (Refereed) Published
Abstract [en]

Cu2ZnSnS4 (TS) is a promising material for thin film solar cells which contains only abundant elements. This work focuses on the stability of elemental composition of films deposited by reactive sputtering of CuSn alloy targets in H2S. Long equilibration times of several hours were observed. The main reason is the formation of a thick Cu2S layer on the target surface. Especially in areas with low erosion rate, the Cu2S thickness reaches up to 700 pm and is accompanied by a preferential loss of Sn from the target. Based on the results, it is suggested that the formation of Cu2S may be limited either by more uniform erosion of the target surface or by reduction of the H2S partial pressure.

Place, publisher, year, edition, pages
2014. Vol. 240, p. 281-285
Keywords [en]
Reactive sputtering, H2S, Sulfides, CZTS, Cu2ZnSnS4, CuSn sputtering
National Category
Natural Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Electronics
Identifiers
URN: urn:nbn:se:uu:diva-222175DOI: 10.1016/j.surfcoat.2013.12.042ISI: 000331989900038OAI: oai:DiVA.org:uu-222175DiVA, id: diva2:711500
Available from: 2014-04-10 Created: 2014-04-08 Last updated: 2018-08-17Bibliographically approved
In thesis
1. Sputtering of Precursors for Cu2ZnSnS4 Solar Cells and Application of Cadmium Free Buffer Layers
Open this publication in new window or tab >>Sputtering of Precursors for Cu2ZnSnS4 Solar Cells and Application of Cadmium Free Buffer Layers
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis is to understand the influence of the deposition process and resulting film properties on Cu2ZnSnS4 (CZTS) thin film solar cells. Two main aspects are studied, namely formation of absorber precursors by sputtering, and alternative Cd-free buffer materials with improved band alignment.

Reactive sputtering is used to grow dense and homogeneous precursor films containing all elements needed for CZTS absorbers. The addition of H2S gas to the inert Ar sputter atmosphere leads to a drastic decrease of Zn-deposition rate due to the sulfurization of the target. Sulfurization also leads to instabilities for targets made of CuSn, Cu and Cu2S, while sputtering from CuS gave acceptable process stability.

The H2S/Ar-ratio also affects film morphology and composition. Precursors with sulfur content close to stoichiometric CZTS have a columnar, crystalline structure. Materials analysis suggests a non-equilibrium phase with a cubic structure, where each S atom is randomly surrounded by 2:1:1 Cu:Zn:Sn-atoms, respectively. Substrate heating during sputtering is shown to be important to avoid cracks in the annealed films while stress in the precursor films is not observed to affect the absorber or solar cell quality.

Sputtering from compound targets in Ar-atmosphere yields precursor properties similar to those from reactive sputtering at high H2S/Ar-ratios and both types can be processed into well-performing solar cells.

Additionally, a low temperature treatment of CZTS absorbers in inert atmosphere prior to buffer layer growth is shown to affect the device properties, which indicates that the thermal history of the CZTS absorber is important.

The alternative buffer system ZnO1-xSx is found to yield lower efficiencies than expected, possibly due to inferior interface or buffer quality. The Zn1-xSnxOy (ZTO) buffers instead give better performance than their CdS references. For optimized parameters, the activation energy for recombination coincides with the energy of the photoluminescence peak of the absorber. This can be interpreted as a shift of dominant recombination path from the interface to the CZTS bulk. A well-performing CZTS-ZTO device with antireflective coating yielded an efficiency of 9.0 %, which at the time of publication was the highest value published for a Cd-free pure-sulfide CZTS solar cell.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 102
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1707
Keywords
solar cells, thin film, buffer layer, sputtering, reactive sputtering, CZTS, kesterite, zinc tin oxide
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-357354 (URN)978-91-513-0414-4 (ISBN)
Public defence
2018-10-05, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2018-09-13 Created: 2018-08-17 Last updated: 2018-10-02

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full text

Authority records

Kubart, TomasEricson, ToveScragg, Jonathan J.Edoff, MarikaPlatzer-Bjorkman, Charlotte

Search in DiVA

By author/editor
Kubart, TomasEricson, ToveScragg, Jonathan J.Edoff, MarikaPlatzer-Bjorkman, Charlotte
By organisation
Solid State Electronics
In the same journal
Surface & Coatings Technology
Natural SciencesEngineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 875 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf