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Influence from front contact sheet resistance on extracted diode parameters in CIGS solar cells
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.
2008 (English)In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 16, no 2, 113-121 p.Article in journal (Refereed) Published
Abstract [en]

The extraction of one-diode model parameters from a current-voltage (J-V) curve is problematic, since the model is one-dimensional while real devices are indeed three-dimensional. The parameters obtained by fitting the model curve to experimental data depend on how the current is collected, and more specifically the geometry of the contact. This is due to the non-uniform lateral current flow in the window layers, which leads to different parts of the device experiencing different front contact voltage drop, and hence different operating points on the ideal J-V curve. In this work, finite element simulations of three-dimensional contact structures are performed and compared to experimental data on Cu(In,Ga)Se2-based solar cell devices. It is concluded that the lateral current flow can influence the extracted parameters from the one-diode model significantly if the resistivity of the front contact material is high, or if there is no current collecting grid structure. These types of situations may appear in damp heat-treated cells and module type cells, respectively.

Place, publisher, year, edition, pages
2008. Vol. 16, no 2, 113-121 p.
Keyword [en]
simulations, CIGS, solar cells, finite element method, one-diode model
National Category
Engineering and Technology
URN: urn:nbn:se:uu:diva-97556DOI: 10.1002/pip.784ISI: 000254412700003OAI: oai:DiVA.org:uu-97556DiVA: diva2:172550
Available from: 2008-09-26 Created: 2008-09-26 Last updated: 2016-04-13Bibliographically approved
In thesis
1. Modelling and Degradation Characteristics of Thin-film CIGS Solar Cells
Open this publication in new window or tab >>Modelling and Degradation Characteristics of Thin-film CIGS Solar Cells
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Thin-film solar cells based around the absorber material CuIn1-xGaxSe2 (CIGS) are studied with respect to their stability characteristics, and different ways of modelling device operation are investigated. Two ways of modelling spatial inhomogeneities are detailed, one fully numerical and one hybrid model. In the numerical model, thin-film solar cells with randomized parameter variations are simulated showing how the voltage decreases with increasing material inhomogeneities.

With the hybrid model, an analytical model for the p-n junction action is used as a boundary condition to a numerical model of the steady state electrical conduction in the front contact layers. This also allows for input of inhomogeneous material parameters, but on a macroscopic scale. The simpler approach, compared to the numerical model, enables simulations of complete cells. Effects of material inhomogeneities, shunt defects and grid geometry are simulated.

The stability of CIGS solar cells with varying absorber thickness, varying buffer layer material and CIGS from two different deposition systems are subjected to damp heat treatment. During this accelerated ageing test the cells are monitored using characterization methods including J-V, QE, C-V and J(V)T. The degradation studies show that the typical VOC decrease experienced by CIGS cells subjected to damp heat is most likely an effect in the bulk of the absorber material.

When cells encapsulated with EVA are subjected to the same damp heat treatment, the effect on the voltage is considerably reduced. In this situation the EVA is saturated with moisture, representing a worst case scenario for a module in operation. Consequently, real-life modules will not suffer extensively from the VOC degradation effect, common in unprotected CIGS devices.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 82 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 554
solar cells, thin-film, chalcogenide, stability, characterization, modelling, simulations, finite element method, CIGS, photovoltaic module
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:uu:diva-9291 (URN)978-91-554-7287-0 (ISBN)
Public defence
2008-10-17, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:30
Available from: 2008-09-26 Created: 2008-09-26Bibliographically approved

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Edoff, Marika
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