Skin Deep: Highlights of NREL Surface Analysis PV Research

The Surface Analysis project provides measurement support and leadership for collaborative research activities involving surface chemistry and physics in all areas of the PV program. Significant results from the past fiscal year include the following: i) in-situ XPS, UPS, and AES studies of chemical-bath exposure of CIGS surfaces demonstrated that Group-III elements are preferentially removedfrom the surface, that type conversion of the surface occurs, and that the addition of a surfactant improves CdS deposition and thus device performance; ii) XPS studies of polyethylene terephthalate (PET) candidate backsheet materials have shown that plasma exposure prior to oxide-barrier deposition results in the formation of low-molecular-weight fragments that result in the formation of a weakinterfacial layer that fails during damp-heat exposure; iii) an empirical relation was derived for the source geometry that leads to optimal film-thickness uniformity in rotating-substrate physical-vapor deposition (PVD) systems; and iv) PVD flux-distribution calculations were performed to develop a novel method for combinatorial thin-film synthesis.