Bulk measurement of copper and sodium content in CuIn(0.7)Ga(0.3)Se(2) (CIGS) solar cells with nanosecond pulse length laser induced breakdown spectroscopy (LIBS)

TL;DR

This paper demonstrates that nanosecond pulse LIBS can rapidly, inexpensively, and non-invasively measure copper and sodium in CIGS solar cells, enabling real-time in-line process monitoring.

Contribution

It introduces a LIBS-based method for measuring elemental content in CIGS solar cells with advantages over existing techniques, including speed, cost, and operational flexibility.

Findings

LIBS spectral lines correlate linearly with SIMS measurements

Nanosecond pulse LIBS effectively ablates CIGS material

Depth resolution of LIBS suitable for in-line monitoring

Abstract

In this work, we show that laser induced breakdown spectroscopy (LIBS) with a nanosecond pulse laser can be used to measure the copper and sodium content of CuIn(0.7)Ga(0.3)Se(2) (CIGS) thin film solar cells on molybdenum. This method has four significant advantages over methods currently being employed: the method is inexpensive, measurements can be taken in times on the order of one second, without high vacuum, and at distances up to 5 meters or more. The final two points allow for in-line monitoring of device fabrication in laboratory or industrial environments. Specifically, we report a linear relationship between the copper and sodium spectral lines from LIBS and the atomic fraction of copper and sodium measured via secondary ion mass spectroscopy (SIMS), discuss the ablation process of this material with a nanosecond pulse laser compared to shorter pulse duration lasers, and examine the depth resolution of nanosecond pulse LIBS.