Temperature-dependent current-voltage and lightsoaking measurements on Cu(In,Ga)Se2 solar cells with ALD-Zn1-xMgxO buffer layers
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
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.
CIGS, ZnMgO, thin film solar cells, recombination, lightsoaking
Engineering and Technology
IdentifiersURN: urn:nbn:se:uu:diva-109854DOI: 10.1002/pip.912ISI: 000270774600003ISBN: 1099-159XOAI: oai:DiVA.org:uu-109854DiVA: diva2:274309