학술논문
Near-Surface [Ga]/([In]+[Ga]) Composition in Cu(In,Ga)Se2 Thin-Film Solar Cell Absorbers: An Overlooked Material Feature
Document Type
article
Author
Source
Physica Status Solidi (A) Applications and Materials Science. 216(18)
Subject
Language
Abstract
The chemical and electronic structures in the near-surface region of Cu(In,Ga)Se2 thin-film solar cell absorbers are investigated using nondestructive soft and hard X-ray photoelectron spectroscopy. In addition to a pronounced surface Cu-depletion, the [Ga]/([In]+[Ga]) composition indicates that the topmost surface is Ga-poor (or In-rich). For the studied depth region, common depth profiling techniques generally fail to provide reliable information and, thus, the near-surface chemical and electronic structure profiles are often overlooked. The relation between the observed near-surface elemental compositions and the derived electronic properties of the absorber material is discussed. It is found that the surface band gap energy crucially depends on the Cu-deficiency of the absorber surface and suggests that it is, in this region, only secondarily determined by the [Ga]/([In]+[Ga]) ratio.