Advanced diagnostic and control methods of processes and layers in CIGS solar cells and modules

Abstract

Process monitoring and quality assessment for Cu(In,Ga)(Se,S)2 (CIGS) absorber layers is discussed. One focus is on laser light scattering (LLS) as a tool for process diagnostics. This technique can give in situ and real-time information about CIGS film growth using sequential as well as evaporation processes. Raman spectroscopy is presented as a method to assess the fundamental structural properties of as-grown films. Experience shows that the specific structure of Raman lines can be interpreted in relation to device performance. Raman spectroscopy is particularly useful for material development and achieving at least average solar cell efficiencies. Time-resolved photoluminescence (TRPL) goes one step further and is generally related to the solar cell performance. It tracks carrier population decay after optical excitation and thus gives quantitative information about the most efficient recombination channels and material quality. It is apt to optimise the absorber of highly efficient devices. We will recommend how to use the three methods appropriately and will discuss requirements for industrial applications. Copyright © 2010 John Wiley & Sons, Ltd.