A closer look at initial CdS growth on high-efficiency Cu(In, Ga)Se<inf>2</inf> absorbers using surface-sensitive methods

Abstract

In this contribution we present further evidence that the post-deposition treatment with alkali elements (PDT) on Cu(In, Ga)Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (CIGS) films can positively influence the initial growth of chemical-bath-deposited CdS. We investigate the surface of CIGS films with and without PDT during initial growth of CdS by various surface-sensitive methods - x-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), and high-resolution scanning electron microscopy - in order to gather information about the growth rate and coverage of CdS on the two surface types. We find that the CdS film deposited for 180 seconds on PDT-CIGS is mostly closed, while samples without PDT show very inhomogeneous coverage. Furthermore, for growth on PDT-CIGS, the effective CdS film thickness is determined to be higher by both XPS and SE. Finally, we present a discussion of the information content of the methods employed here.