Epitaxial Emitter Optimization for High-Efficiency Silicon Solar Cells

Abstract

Production of silicon substrates using epitaxial CVD is a leading “kerf-less” technology candidate for substantially improving silicon usage. Epitaxy provides an opportunity for realizing a much wider variety of dopant profiles in the bulk and for the emitters than can be achieved with solid-state diffusion methods. The in-situ epitaxial doped layers also eliminate steps from the cell production process for further cost reductions. This paper reports on optimization of epitaxial emitter profiles. A key feature of epitaxial emitters is a large reduction in Joe and of heavy doping effects through use of thick, lightly doped emitters. Using device structures that are entirely consistent with current production techniques, we show that the efficiency is improved by over 1% absolute by using epitaxial emitters compared to conventional emitter technology with bulk wafers.