Title :
XPS AND UPS investigation of NH4OH-exposed Cu(In,Ga)Se2 thin films
Author :
Perkins, Craig L. ; Hasoon, Falah S. ; Al-Thani, Hamda A. ; Asher, Sally E. ; Sheldon, Pete
Author_Institution :
Nat. Renewable Energy Lab., USA
Abstract :
Photoelectron spectroscopy was used to determine the compositional and electronic changes occurring in Cu(In,Ga)Se2 thin films as a result of immersion in aqueous ammonia solution. We find that NH4OH-treated CIGS surfaces are preferentially etched of indium and gallium, resulting in the formation of a thin layer of a degenerate Cu-Se compound that we tentatively identify as Cu2Se. The work function of ammonia-treated samples is found to increase by 0.6 eV relative to as-grown CIGS thin films. The uniformity of chemical bath effects (etching & deposition) was found to be improved by the addition to the bath of a non-ionic surfactant. Initial device results show that the new surfactant-based chemical bath deposition (CBD) method may lead to better and thinner CdS buffer layers.
Keywords :
X-ray photoelectron spectra; buffer layers; copper compounds; etching; gallium compounds; indium compounds; liquid phase deposition; semiconductor thin films; surfactants; thin film devices; ultraviolet photoelectron spectra; work function; CdS buffer layers; Cu(InGa)Se2; NH4OH-exposed Cu(In,Ga)Se2 thin films; NH4OH-treated CIGS surfaces; UPS; XPS; ammonia-treated samples; aqueous ammonia solution; chemical bath effects; degenerate Cu-Se compound; deposition; nonionic surfactant; photoelectron spectroscopy; preferential etching; surfactant-based chemical bath deposition; work function; Buffer layers; Chemicals; Etching; Gold; Heterojunctions; Photoelectricity; Renewable energy resources; Spectroscopy; Transistors; Uninterruptible power systems;
Conference_Titel :
Photovoltaic Specialists Conference, 2005. Conference Record of the Thirty-first IEEE
Print_ISBN :
0-7803-8707-4
DOI :
10.1109/PVSC.2005.1488117
