Plasma-Assisted Coevaporation of S and Se for Wide Band Gap Chalcopyrite Photovoltaics: Phase I Annual Report; December 2001-December 2002

In this work, ITN Energy Systems (ITN) and lower-tier subcontractor Colorado School of Mines (CSM) explore the replacement of the molecular chalcogen precursors during deposition (e.g., Se2 or H2Se) with more reactive chalcogen monomers or radicals (e.g., Se). Molecular species will be converted to atomic species in a low-pressure inductively coupled plasma. The non-equilibrium environmentcreated by the plasma will allow control over the S/Se ratio in these films. Tasks of the proposed program center on developing and validating monoatomic chalcogen chemistry, tuning of low-pressure monomer chalcogen sources, and evaluating plasma-assisted coevaporation (PACE) for CIGS coevaporation. Likely advantages of deposition by plasma-enhanced coevaporation include: a)provides potentialfor lower deposition temperature and/or for better film quality at higher deposition temperature; b) provide potential for decreased deposition times; c) provides high material utilization efficiency (~90%) that results in less deposition on other parts of the reactor, leading to lower clean-up and maintenance costs, as well as longer equipment lifetime; d) high material utilization efficiencyalso reduces the total operating pressure, which is beneficial for the design and control of metal coevaporation (advantages include minimal metal-vapor beam spread and lower source operating temperatures); e) enables deposition of wide-bandgap copper indium gallium sulfur-selenide (CIGSS) films with controlled stoichiometry.