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Simulating Material Inhomogeneities and Defects in CIGS Thin-film 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.
2009 (English)In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 17, no 5, 306-314 p.Article in journal (Refereed) Published
Abstract [en]

Thin-film CIGS solar cells are simulated using a hybrid model   consisting of a distributed form of the analytical one diode model   paired with a numerical finite element model of the d.c. conduction in   the front contact layers. Variations in material quality over the   substrate surface., from measured J-V curves, are incorporated into the   model and the effects of cell width and window layer thickness are evaluated for homogeneous and inhomogeneous material quality. Furthermore, the effects of discrete shunt defects of different sizes   are modelled, and in different positions on the cell surface. The  results from optimizing cell width and window layer thickness show that   the effects of material inhomogeneities include a small shift of the   optimal parameters together with a less pronounced maximum. As   expected, the defect size is important to the shunt conductance   parameter of the resulting J-V curves. The passivating effect of the highly resistive ZnO layer is confirmed.

Place, publisher, year, edition, pages
2009. Vol. 17, no 5, 306-314 p.
Keyword [en]
modelling, simulation, CIGS, solar cells, photovoltaic module
National Category
Engineering and Technology
URN: urn:nbn:se:uu:diva-97557DOI: 10.1002/pip.888ISI: 000268433900004OAI: oai:DiVA.org:uu-97557DiVA: diva2:172551
Available from: 2008-09-26 Created: 2008-09-26 Last updated: 2016-04-14Bibliographically 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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