Experimental study of boric acid diffused emitters for n-type c-Si solar cells

Abstract

In this work, boric acid powder solution has been used as a dopant source for optimizing emitter sheet resistance values corresponding to temperature range 850°-900°C. High purity (99.999%), non-toxic and low-cost boron diffusion is found to be suitable for p or p+ emitters with minimum diffusion-induced defects. Formation of a boron-rich layer, which is considered as a major problem in B-diffusion is eliminated with introduction of controlled process steps. An increase of effective minority carrier lifetime is observed after the diffusion process. The measured Sun's Voc and Implied Voc for sheet resistances less than 100Ω/sq is in the range of 570-600 mV, without any optics-improving techniques, for Czochralski n-type c-Si wafers. This indicates the suitability of the use of boric acid as the dopant source for emitter formation in n-type c-Si solar cells.