Chemical interaction at the buried silicon/zinc oxide thin-film solar cell interface as revealed by hard X-ray photoelectron spectroscopy

Abstract

Highlights We used HAXPES to identify chemical interactions at the buried silicon/aluminum-doped zinc oxide thin-film solar cell interface.  The results indicate a diffusion of zinc and aluminum into the silicon upon annealing procedures which are part of the solar cell processing.  The contamination of the silicon may be detrimental for the solar cell performance.

Influence of atmosphere and material properties on damp heat stability of ZnO:Al

“…After the annealing the silicon layer commonly is removed by reactive plasma etching using NF3 or SF6 as etching gas. To ensure the total removal of the chemically intermixed layer of less than 10 nm at the interface between silicon and ZnO:Al we applied further etching steps after the plasma treatment. These comprise either physical etching by an argon ion beam or chemical etching in hydrochloric (0.05 w/w% HCl) or hydrofluoric acid (1 w/w% HF).…”

“…We suggested a reconstruction at the grain boundaries to cause this stability against damp heat tests. However, an interdiffusion at the interface between silicon and ZnO:Al during annealing is known and one could speculate that this SiZn x Al y O z layer might be resistive to the plasma etching and could have acted as a protective barrier against water penetration.…”

HAXPES studies of solid materials for applications in energy and information technology using the HIKE facility at HZB-BESSY II

“…The calculations were performed within the local-density approximation. 21 We used the full potential linearized augmented plane-wave ͑FPLAPW͒ band-structure method as implemented in the WIEN2K package. 22 These calculations include self-consistent screening processes of all electrons in the supercell of 32 atoms.…”