uu.seUppsala University Publications
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
Temperature-dependent current-voltage and lightsoaking measurements on Cu(In,Ga)Se2 solar cells with ALD-Zn1-xMgxO buffer layers
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. (Solcellsgruppen)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. (Solcellsgruppen)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. (Solcellsgruppen)
2009 (English)In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 17, no 7, 460-469 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, lightsoaking and temperature-dependent current-voltage (JVT) measurements on Cu(In,Ga)Se2 solar cells with atomic layer deposited Zn1-xMgxO buffer layers are presented. A range of Mg concentrations are used, from pure ZnO (x=0) to 26% Mg (x=0·26). Since this kind of solar cells exhibit strong metastable behaviour, lightsoaking is needed prior to the JVT-measurements to enable fitting of these to the one-diode model. The most prominent effect of lightsoaking cells with Mg-rich buffer layers is an increased fill factor, while the effect on cells with pure ZnO buffer is mainly to increase Voc·. The activation energy is extracted from JVT-measurement data by applying three different methods and the ideality factors are fitted to two different models of temperature-dependence. A buffer layer consisting either of ZnO or Zn1-xMgxO with a minor Mg content gives solar cells dominated by interface recombination, which probably can be related to a negative conduction band offset. A relatively high Mg content in the buffer layer (x=0·21) leads to solar cells dominated by recombination in the space charge region. The recombination is interpreted as being tunnelling-enhanced. The situation in between these Mg concentrations is less clear. Before lightsoaking, the sample with x=0·12 has the highest efficiency of 15·3%, while after lightsoaking the sample with x=0·21 holds the best efficiency, 16·1%, exceeding the value for the CdS reference. The Jsc values of the Zn1-xMgxO cells surpass that of the reference due to the larger bandgap of Zn1-xMgxO compared to CdS.

Place, publisher, year, edition, pages
2009. Vol. 17, no 7, 460-469 p.
Keyword [en]
CIGS, ZnMgO, thin film solar cells, recombination, lightsoaking
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-109854DOI: 10.1002/pip.912ISI: 000270774600003ISBN: 1099-159X (print)OAI: oai:DiVA.org:uu-109854DiVA: diva2:274309
Available from: 2009-10-28 Created: 2009-10-28 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Modelling Band Gap Gradients and Cd-free Buffer Layers in Cu(In,Ga)Se2 Solar Cells
Open this publication in new window or tab >>Modelling Band Gap Gradients and Cd-free Buffer Layers in Cu(In,Ga)Se2 Solar Cells
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A deeper understanding of Cu(In,Ga)Se2 (CIGS) solar cells is important for the further improvement of these devices. This thesis is focused on the use of electrical modelling as a tool for pursuing this aim. Finished devices and individual layers are characterized and the acquired data are used as input in the simulations. Band gap gradients are accounted for when modelling the devices. The thesis is divided into two main parts. One part that treats the influence of cadmium free buffer layers, mainly atomic layer deposited (Zn,Mg)O, on devices and another part in which the result of CIGS absorber layer modifications is studied. Recombination analysis indicates that interface recombination is limitting the open circuit voltage (Voc) in cells with ZnO buffer layers. This recombination path becomes less important when magnesium is introduced into the ZnO giving a positive conduction band offset (CBO) towards the CIGS absorber layer. Light induced persistent photoconductivity (PPC) is demonstrated in (Zn,Mg)O thin films. Device modelling shows that the measured PPC, coupled with a high density of acceptors in the buffer-absorber interface region, can explain light induced metastable efficiency improvement in CIGS solar cells with (Zn,Mg)O buffer layers. It is shown that a thin indium rich layer closest to the buffer does not give any significant impact on the performance of devices dominated by recombination in the CIGS layer. In our cells with CdS buffer the diffusion length in the CIGS layer is the main limitting factor. A thinner CIGS layer improves Voc by reducing recombination. However, for thin enough absorber layers Voc deteriorates due to recombination at the back contact. Interface recombination is a problem in thin devices with Zn(O,S) buffer layers. This recombination path is overshadowed in cells of standard thickness by recombination in the CIGS bulk. Thin cells with Zn(O,S) buffer layers have a higher efficiency than CdS cells with the same absorber thickness.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 70 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 900
Keyword
CIGS, Thin film solar cells, Electrical modelling, Alternative buffer layers, Gallium gradients, Simulations, Electrical characterization, Metastabilities, Light-soaking, Hall measurements, Persistent photoconductivity
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Materials Engineering Physical Sciences
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-168618 (URN)978-91-554-8280-0 (ISBN)
Public defence
2012-03-30, Polhemssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2012-03-09 Created: 2012-02-13 Last updated: 2013-04-08Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Authority records BETA

Pettersson, JonasPlatzer-Björkman, CharlotteEdoff, Marika

Search in DiVA

By author/editor
Pettersson, JonasPlatzer-Björkman, CharlotteEdoff, Marika
By organisation
Solid State Electronics
In the same journal
Progress in Photovoltaics
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

doi
isbn
urn-nbn

Altmetric score

doi
isbn
urn-nbn
Total: 937 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