Pore cathode for the mass production of photovoltaic devices having increased conversion efficiency

Abstract

A pore cathode for use in a deposition chamber for the plasma enhanced deposition of photovoltaic materials onto one or more webs of substrate material. The cathode is planar and serves the dual functions of (1) an electrode for the plasma deposition process and (2) a distribution conduit for the flow of fresh reaction gas to and for the evacuation of the spent reaction gas from the plasma region to maintain a uniform, constant pressure plasma reaction. The gas outlet pores of the inventive cathode are uniquely sized, shaped and spaced to provide new plasma chemistry and physics to insure optimization of the zoo of chemical species within the plasma regardless of deposition speed. That is, the distribution of ions, electrons, free radicals and neutral species in the plasma are optimized to deposit high quality photovoltaic semiconductor material while also increasing the utilization of the process gases, thus allowing the economical mass production of amorphous silicon solar cells having at least 8% photovoltaic efficiency on large area substrates. The pores can be covered by gas dispersion plates which prevent direct, line-of-sight, flow of the process gases to the adjacent deposition substrate and more uniformly distributes the gases flowing into the plasma region between the cathode and the substrate, thus minimizing the effects of non-homogeneity of the depositing species.

Dependencies are inferred from the claim text.