Investigation of Defect Properties in Cu(In,Ga)Se2 Solar Cells by Deep-Level Transient Spectroscopy

L. L. Kerr, Sheng S. Li, S. W. Johnston, T. J. Anderson, O. D. Crisalle, W. K. Kim, J. Abushama, R. N. Noufi

Research output: Contribution to journalArticlepeer-review

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Abstract

The performance of the chalcopyrite material Cu(In,Ga)Se2 (CIGS) used as an absorber layer in thin-film photovoltaic devices is significantly affected by the presence of native defects. The deep-level transient spectroscopy (DLTS) technique is used in this work to characterize the defect properties, yielding relevant information about the defect types, their capture cross-sections, and energy levels and densities in the CIGS cells. Three solar cells developed using different absorber growth technologies were analyzed using DLTS, capacitance-voltage (C-V), and capacitance-temperature (C-T) techniques. It was found that CIS cells grown at the University of Florida exhibits a middle-gap defect level that may relate to the cell's low fill factor and open-circuit voltage values observed. A high efficiency (ηc>18%) CIGS cell produced by the National Renewable Energy Laboratory (NREL) was found to contain three minority-carrier (electron) traps and a 13% CIGS cell produced by the Energy Photovoltaics Inc. (EPV) exhibited one majority (hole) trap. The approach followed using the DLTS technique serves as a paradigm for revealing the presence of significant defect levels in absorber materials, and may be used to support the identification of remedial processing operations.

Original languageAmerican English
Pages (from-to)1579-1586
Number of pages8
JournalSolid State Electronics
Volume48
Issue number9
DOIs
StatePublished - 2004

NREL Publication Number

  • NREL/JA-520-36913

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