Analysis of Copper Indium Gallium Selenide (CIGS) Solar Cells with ARL QUANT’X EDXRF Spectrometer

Significance of the Topic

Copper Indium Gallium Selenide (CIGS) solar cells represent a high-efficiency photovoltaic technology due to their direct bandgap and strong light absorption, enabling thinner active layers and reduced material usage. Rapid, non-destructive analysis of layer composition and thickness is essential for quality control, process optimization and reliability assessment in both research and industrial production of CIGS devices.

Study Objectives and Overview

This application note demonstrates the use of an ARL QUANT’X energy-dispersive X-ray fluorescence (EDXRF) spectrometer for fast, accurate determination of elemental composition and layer thickness in CIGS solar cells. Key goals include validating measurement repeatability, assessing precision for major constituents (Cu, In, Ga, Se, Mo), and illustrating the fundamental-parameters (FP) based quantification workflow in WinTrace software.

Applied Methodology and Instrumentation

The ARL QUANT’X EDXRF system features a 50 W air-cooled Rh X-ray tube with a 0.05 mm Be window and a 30 mm2 silicon-drift detector (SDD). Nine primary beam filters optimize excitation conditions. Samples are analyzed directly without special preparation, using a CCD camera for precise positioning. Two tube voltages (30 kV with a Pd thick filter for Cu, Ga, Se; 50 kV with a thin Cu filter for In, Mo) and 30 s live time per condition in ambient air generate high-quality spectra. Fundamental-parameters thin-film routines within WinTrace require only layer count and elemental contents for calibration, employing bulk and thin-film standards.

Main Results and Discussion

Repeatability tests on standard CIGS modules (with and without Cu) involved ten consecutive measurements. For the full-composition cell, average CIGS thickness was 1.295 µm (RSD ≤ 0.5 %), and elemental concentrations showed RSD < 1 % (Ga ≈ 1.5 %). The copper-free variant exhibited 1.116 µm thickness and < 1 % RSD in In, Se, Ga, confirming robust layer modeling. Extending measurement time at 30 kV further improves Ga precision below 1 %.

Benefits and Practical Applications

• Non-destructive, rapid analysis suitable for inline or batch QC in CIGS manufacturing.
• High repeatability for thickness and composition without elaborate sample prep.
• Flexible FP-based software handles multi-layer stacks with minimal input.
• Unattended operation enabled by optional sample changer and CCD alignment.

Future Trends and Potential Uses

Advances in detector technology and software algorithms will further reduce analysis times and expand detectable elements. Integration with in-line process monitoring and machine learning models may enable real-time feedback control in thin-film deposition. Broader adoption of EDXRF for emerging tandem and multi-junction cells is anticipated, leveraging the same non-destructive advantages.

Conclusion

The ARL QUANT’X EDXRF spectrometer delivers accurate, non-destructive quantification of CIGS solar cell layers with excellent repeatability and minimal sample handling. Fundamental-parameters based thin-film methods streamline calibration and analysis, supporting quality assurance and R&D workflows in photovoltaics.

Reference

Lemberge P. Analysis of Copper Indium Gallium Selenide (CIGS) Solar Cells with ARL QUANT’X EDXRF Spectrometer. Thermo Fisher Scientific Application Note AN41962, 2019.