Development of a self-aligned etch-back process for selectively doped silicon solar cells

Abstract

Selectively doped (SD) solar cells have advantages of lower front diffusion recombination, lower contact resistivity and better blue response. In this work, a simple, self-aligned SD solar cell process is presented, eliminating the critical mask alignment step in current SD solar cells. In the new process, the front metal grid is deposited on top of a heavy phosphorus diffusion before the anti-reflection coating. The metal grid, formed in this experiment by evaporating aluminum through a shadow mask, acts as mask during a subsequent etch-back step, which therefore results in a heavily doped region (∼18 ω/sq) under the metal fingers and a lightly doped region (∼100 ω/sq) elsewhere. This etch-..