Etch Back Selective Emitter Process with Single POCl3 Diffusion

Abstract

Selective emitter by etch back is an easy method to obtain a better blue response and lower contact resistivity and therefore to improve the performance of a solar cell. To achieve a selective emitter with only one diffusion step provides a cost reduction. In this work it is shown that it is possible to achieve a selective emitter by etch back with commercial etching paste applied by screen printing. Both activation of the etching paste and cleaning afterwards can be done with inline production equipment. Accurate alignment of the screen printed front side grid is essential. The selective emitter cells show a big improvement in open circuit voltage and efficiency. It is shown that the improvements are due to a better IQE and lower front side recombination.